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DESCRIPTION JP2007214726

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DESCRIPTION JP2007214726
The present invention provides an audio signal output device in which the problem of sound
leakage between first and second channels is reduced by simple signal processing without using
a special terminal such as a 4-pole terminal. A three-pole terminal provided with an output
terminal 28L of a first channel audio signal, an output terminal 28R of a second channel audio
signal, and a common ground terminal 28C. The first channel audio signal is added to the second
channel audio signal reduced according to the sound leakage ratio of the second channel audio
signal to the first sound reproducing unit, and supplied to the output terminal of the first channel
audio signal. , Adding the first channel audio signal reduced according to the sound leakage ratio
of the first channel audio signal to the second audio reproduction unit to the second channel
audio signal, and supplying it to the output terminal of the second channel audio signal Sound
leakage cancellation signal addition means 30, 40 are provided. [Selected figure] Figure 1
Audio signal output device and sound leakage reduction method
[0001]
The present invention relates to an audio signal output device such as a music player that
outputs left and right two-channel stereo audio signals, for example, to headphones for sound
reproduction, and more particularly to an invention for reducing sound leakage between
channels.
[0002]
2. Description of the Related Art Portable music players that use headphones as sound
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1
reproduction means to sound reproduce stereo audio signals of left and right two channels are in
widespread use.
In this case, the connection between the music player and the headphones is generally performed
using a jack and a plug using a three-pole terminal. Here, in the case of the left and right twochannel stereo signals, the three-pole terminal is a terminal for the left channel audio signal, a
terminal for the right channel audio signal, and a ground terminal (ground) common to the left
and right channel audio signals. And three terminals.
[0003]
FIG. 8 shows the music player 200 and the headphones 100 connected thereto. The headphone
100 includes a headphone unit 10L for the left channel, a headphone unit 10R for the right
channel, a connection plug 101 including a three-pole terminal, a headphone unit 10L for the left
channel, and a headphone unit 10R for the right channel. And a cable 102 for connecting the
cable 101 with the cable 101.
[0004]
The cable 102 includes a connecting portion 103 for the left and right channel cables. The
ground sides of the left and right channels are commonly connected by the connecting portion
103, and the common connection point is connected to the common ground terminal COM of the
connection plug 101.
[0005]
The connection plug 101 is a three-pole terminal including a left channel signal terminal portion
L +, a right channel signal terminal portion R +, and a common ground terminal portion COM.
[0006]
The music player 200 is provided with a headphone jack 201 composed of a three-pole terminal
corresponding to the connection plug 101 of the headphone 100.
By inserting the connection plug 101 of the headphone 100 into the headphone jack 201 of the
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2
music player 200, the two-channel stereo audio signal output from the music player 200 is
acoustically reproduced by the headphone units 10L and 10R for the left and right channels of
the headphone 100. Ru.
[0007]
However, in the case of using the three-pole terminal as described above, there is a problem of
sound leakage between the left and right channels.
This sound leakage is a combination of the common ground terminal for the left channel and
right channel audio signals at the 3-pole terminal and the resistance component included in the
cable 102 of the headphone 100 and the amplifier characteristics of the music player 200. It is
known to occur. The sound leakage problem will be further described.
[0008]
FIG. 9 is an equivalent connection circuit diagram for explaining that a sound leak occurs when
the connection plug 101 of the headphone 100 is inserted into the headphone jack 201 of the
music player 200. In FIG. 9, in order to explain the case where the left channel audio signal leaks
to the right channel, it is assumed that the left channel audio signal is a large amplitude signal
and the right channel is completely silent. Further, it is assumed that the gain of the amplifier
unit of the music player 200 is one.
[0009]
As shown in FIG. 9, the left channel large amplitude audio signal (referred to as an analog audio
signal) from the left channel signal source 1L passes through the amplifier 2L having a gain of 1
and the resistor 3L, and the left channel audio signal output of the headphone jack 201 It is
supplied to the terminal 4L.
[0010]
A right channel signal (an analog audio signal) from the right channel signal source 1R is
supplied to the right channel audio signal output terminal 4R of the headphone jack 201 through
an amplifier 2R and a resistor 3R having a gain of 1.
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[0011]
In FIG. 9, the terminal 4 </ b> C grounded in the music player 200 is a common ground terminal
of the headphone jack 201.
The headphone jack 201 is configured as a three-pole terminal including a left channel audio
signal output terminal 4L, a right channel audio signal output terminal 4R, and a common
ground terminal 4C.
[0012]
In the state where the connection plug 101 of the headphone 100 is inserted and connected to
the headphone jack 201, as shown in FIG. 9, for the left channel between the left channel audio
signal output terminal 4L and the common ground terminal 4C. The headphone unit 10L is
connected, and the headphone unit 10R for the right channel is connected between the right
channel audio signal output terminal 4R and the common ground terminal 4C.
[0013]
Then, as shown in FIG. 9, between the left channel audio signal output terminal 4L and the
headphone unit 10L for the left channel, the line resistance 11L of the cable 102, and for the
right channel audio signal output terminal 4R and the right channel The line resistors 11R of the
cable 102 are respectively present between the headphone unit 10R, and the common
connection point 13C on the ground side of the left and right channels, the headphone unit 10L
for the left channel, and the headphone unit 10R for the right channel The line resistances 12L
and 12R are present respectively, and the common line resistance 14C is present between the
common connection point 13C and the common ground terminal 4C.
[0014]
In the connection circuit configuration as described above, the large amplitude audio signal of
the left channel output from the left channel audio signal output terminal 4L passes through the
headphone unit 10L for the left channel, and then is connected to the common ground terminal
4C. It reaches the connection point 13C and flows to the common ground terminal 4C.
[0015]
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However, the common connection point 13C is also connected to the headphone unit 10R for the
right channel, and the large amplitude audio signal of the left channel is transmitted to the
headphone unit 10R for the right channel in combination with the presence of the common line
resistance 14 and the like. It will be in the state where it leaks and is supplied.
As a result, although the right channel audio signal should not exist (is zero) in FIG. 9, the right
channel headphone unit 10R generates a sound wave from the leaked left channel audio signal
supplied. It will be done.
[0016]
The above description is for the case where the left channel audio signal is a large amplitude
audio signal and the right channel is completely silent, and the sound leakage of the left channel
audio signal to the right channel headphone unit 10R is described. However, when the right
channel audio signal is a large amplitude audio signal and the left channel is completely silent,
sound leakage of the right channel audio signal to the left channel headphone unit 10L occurs in
the same manner as described above.
[0017]
Here, the magnitude of the signal leaked to the headphone unit 10R for the right channel has a
coefficient 1 / ML (where ML is a factor according to the line resistance, the characteristics of the
headphone 100, etc.) to the amplitude AL of the left channel audio signal. It becomes size AL /
ML which multiplied> 1).
In addition, the magnitude of the signal leaked to the left channel headphone unit 10L is a factor
1 / MR according to the line resistance, the characteristics of the headphone 100, etc. 1) It
becomes size AR / MR which multiplied.
In this specification, these coefficients 1 / ML and 1 / MR are referred to as sound leakage ratios.
[0018]
The sound leakage ratio 1 / ML of the left channel audio signal to the right channel and the
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sound leakage ratio 1 / MR of the right channel audio signal to the left channel are not
necessarily the same.
[0019]
Conventionally, in order to solve the problem of sound leakage between the left and right
channels, as shown in FIGS. 10 and 11, a method using a 4-pole terminal has been provided (see
Non-Patent Document 1 described later).
That is, as shown in FIG. 10, the headphone 100 'in this example is provided with a connection
plug 104 consisting of a four-pole terminal instead of the connection plug 101 consisting of a
three-pole terminal.
The other configuration of the headphone 100 'is the same as that of the headphone 100
described with reference to FIG.
[0020]
In this case, as shown in FIG. 10, the connection plug 104 includes a left channel signal terminal
portion L +, a right channel signal terminal portion R +, a left channel ground terminal portion
L−, and a right channel ground terminal portion R−. And has a four-pole terminal configuration.
[0021]
FIG. 11 is an equivalent connection circuit diagram in a state in which the connection plug 104
of the 4-pole terminal of the headphone 100 ′ is inserted into the headphone jack of the music
player 200.
In FIG. 11 as well as FIG. 9 described above, the left channel audio signal is a large amplitude
signal and the right channel is completely silent in order to explain the case where the left
channel audio signal leaks to the right channel. Suppose that there is.
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Further, it is assumed that the gain of the amplifier unit of the music player 200 is one.
[0022]
As shown in FIG. 11, in the case of using the connection plug 104 consisting of four-pole
terminals, a music player is used as a connection point between the left channel ground terminal
portion L− of the connection plug 104 and the ground terminal of the headphone jack 201. The
left channel ground terminal 5L 200 is configured, and the right channel ground terminal
portion R− of the connection plug 104 and the ground terminal of the headphone jack 201 are
connected to the ground terminal 5R for the R channel of the music player 200. Is configured.
[0023]
Therefore, in the case of using the connection plug 104 formed of the four-pole terminal, the
common connection point 13C and the common line resistance 14C do not exist as in the case of
the three-pole terminal described with reference to FIG. After passing through the left channel
headphone unit 10L, the large amplitude audio signal of the channel is supplied to the ground
terminal 5L, and the problem of sound leakage from the left channel to the right channel is
avoided.
[0024]
In the case of using the connection plug 104 consisting of four-pole terminals, the problem of
sound leakage from the right channel to the left channel is similarly avoided.
[0025]
The above non-patent documents are as follows.
SHARP “Having a Mobile 1-Bit Digital Amplifier-HA to Achieve High-Quality Sounds Faithful to
Original Sounds”, [online], [Jan. 30, 2006 Search], Internet <URL: http: /
/www.sharp.co.jp/products/mdds700/text/1bit.html>
[0026]
As described above, according to the method using the connection plug composed of the four-
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7
pole terminal, the problem of sound leakage between the left and right channels can be avoided.
However, the connection plug consisting of the four-pole terminal is not a general one and is a
special one, which forces the user to purchase the special headphone, which is not preferable.
[0027]
Although the above description is for the left and right two-channel stereo audio signal, for
example, when the left channel is replaced with the first channel and the right channel is
replaced with the second channel, these first channel audio signals and The same problem arises
in the case where sound reproduction of audio signals other than left and right two-channel
stereo signals is considered as the second channel audio signal.
[0028]
SUMMARY OF THE INVENTION It is an object of the present invention to provide an apparatus
and method capable of alleviating the problem of sound leakage between the first and second
channels described above by simple signal processing without using a special 4-pole terminal as
described above. I assume.
[0029]
In order to solve the above-mentioned problems, the present invention provides an output
terminal of a first channel audio signal, an output terminal of a second channel audio signal, and
a common to the first channel audio signal and the second channel audio signal. A three-pole
terminal including a ground terminal, wherein a first sound reproducing unit for sound
reproducing the first channel audio signal and a second sound reproducing unit for sound
reproducing the second channel audio signal are connected, A three-pole terminal to which an
external terminal having a terminal corresponding to a three-pole terminal is connected; and a
reduction according to a sound leakage ratio of the second channel audio signal to the first sound
reproducing unit to the first channel audio signal The second channel audio signal is added, and
the output end of the first channel audio signal is added. And the first channel audio signal
reduced according to the sound leakage ratio of the first channel audio signal to the second
sound reproducing unit. The audio signal output device is provided with sound leakage
cancellation signal addition means for supplying to the output terminal of the second channel
audio signal.
[0030]
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8
According to the present invention having the above-described configuration, the second channel
audio signal component corresponding to the sound leakage component coming from the second
channel audio signal side to the first sound reproduction unit is added to the first channel audio
signal in advance. .
For this reason, in the first sound reproduction unit, the second channel audio signal component
added to the first channel audio signal and the sound leakage component coming from the
second channel audio signal side cancel each other, and the sound leakage component is It is
canceled.
[0031]
Similarly, the first channel audio signal component corresponding to the sound leakage
component arriving from the first channel audio signal side to the second sound reproduction
unit is added to the second channel audio signal in advance.
Therefore, in the second sound reproduction unit, the first channel audio signal component
added to the second channel audio signal and the sound leak component coming from the first
channel audio signal side cancel each other, and the sound leak component is It is canceled.
[0032]
According to the present invention, the problem of sound leakage between the first and second
channels can be alleviated by simple signal processing without using a special 4-pole terminal.
[0033]
Hereinafter, an embodiment of an audio signal output device according to the present invention
will be described with reference to the drawings, taking as an example a case where a left and
right two-channel stereo signal is applied to a music player that reproduces sound using
headphones.
[0034]
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9
First Embodiment FIG. 2 is a block diagram showing a configuration example of a music player
300 according to a first embodiment.
The music player of this example includes, for example, a hard disk drive, a semiconductor
memory or an optical disk drive, and includes a music content storage unit 21 for storing data of
music content, and a control unit 301 configured using a microcomputer, The operation input
unit 302 is provided.
[0035]
The music player according to this embodiment is provided with a headphone jack 28 having a
three-pole terminal configuration, and the headphone jack 28 is connected by the three-pole
terminal of the headphone 100 as shown in FIG. 8 described above. The plug 101 is configured
to be inserted.
That is, the headphone jack 28 of the music player of this embodiment includes three-pole
terminals of an output terminal 28L of the left channel audio signal, an output terminal 28R of
the right channel audio signal, and a common ground terminal 28C.
[0036]
The control unit 301 controls to read out the music content selected by the user from the music
content storage unit 21 in response to the user's selection input of the music content through the
operation input unit 302 and the reproduction request thereof.
[0037]
The music data of the music content read from the music content storage unit 21 is supplied to
the music data decoding unit 22 and decoded.
Then, the music data decoding unit 22 outputs digital audio signals (PCM (Pulse Code
Modulation) audio signals) DL and DR of left and right two channels.
10-04-2019
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[0038]
The digital audio signals DL and DR are supplied to D / A converters 23L and 23R, respectively,
converted to analog audio signals, and then supplied to the switch circuit 24.
[0039]
In this example, the switch circuit 24 and the switch circuit 26 described later are provided to
allow the user to select the case of performing the sound leakage countermeasure process for the
left and right channels and the case where the sound leakage countermeasure process is not
performed. It is done.
Then, in accordance with the user's selection input of the presence / absence of the sound
leakage countermeasure through the operation input unit 302, the control unit 301 supplies the
switch control signal SW to the switch circuit 24 and the switch circuit 26.
[0040]
When the user does not perform the sound leakage countermeasure process via the operation
input unit 302 and the selection operation is input, the control unit 301 switches the switch
circuit 24 and the switch circuit 26 to the switching state of FIG. 2 as the switching control signal
SW. Control signals are supplied to the switch circuit 24 and the switch circuit 26.
[0041]
Then, at this time, the analog audio signals of the left and right two channels from the D / A
converter 23L and the D / A converter 23R are respectively supplied to the switch circuit 26
through the analog amplifier 25L and the analog amplifier 25R.
At this time, since the switch circuit 26 is switched to the state shown in FIG. 2, the left and right
channel analog audio signals are transmitted through the resistors 27L and 27R respectively to
the left channel audio signal output terminal 28L and the right channel audio signal. It is
supplied to each of the output terminals 28R.
[0042]
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11
Further, when the user performs the sound leakage countermeasure processing through the
operation input unit 302 and the selection operation is input, the control unit 301 sets the switch
circuit 24 and the switch circuit 26 as the switching control signal SW in the reverse of the
switching state of FIG. A control signal for switching to the state is supplied to the switch circuit
24 and the switch circuit 26.
[0043]
Then, at this time, the analog audio signals of the two left and right channels from the D / A
converter 23L and the D / A converter 23R are supplied to the sound leakage cancellation signal
addition unit 30.
The sound leakage cancellation signal addition unit 30 performs processing for adding a signal
for canceling the sound leakage between the left and right channels to each of the left channel
audio signal and the right channel audio signal as described later.
[0044]
The two left and right channel analog audio signals OL and OR to which the sound leakage
cancellation signals from the sound leakage cancellation signal addition unit 30 have been added
are transmitted to the left through the switch circuit 26 and the resistors 27L and 27R,
respectively. A channel audio signal output terminal 28L and a right channel audio signal output
terminal 28R are respectively supplied.
[0045]
Next, FIG. 1 illustrates that in the first embodiment, in a state where the connection plug 101 of
the headphone 100 is inserted into the headphone jack 28 of the music player 300, the sound
leakage is canceled and reduced. It is an equivalent connection circuit diagram for.
[0046]
In FIG. 1, even if the left channel audio signal is a large amplitude signal and the right channel is
completely silent, the sound leakage of the left channel audio signal to the right channel is
canceled and reduced. It shows what is being done.
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Note that the signal source 20L indicates a signal source of the digital audio signal DL of the left
channel from the music data decoding unit 22, and the signal source 20R indicates a digital
audio signal DL of the right channel from the music data decoding unit 22. Signal source of
[0047]
A detailed configuration example of the sound leakage cancellation signal addition unit 30 in the
music player 300 according to the first embodiment is as shown in FIG.
The sound leakage cancellation signal addition unit 30 in the first embodiment is a configuration
of an analog signal processing circuit.
[0048]
That is, in the sound leakage cancellation signal addition unit 30 in this embodiment, the analog
audio signal of the left channel from the D / A converter 23L is supplied to the addition unit 32L
through the amplifier 31L for left channel analog output. The right channel analog audio signal
from the D / A converter 23R is supplied to the addition unit 32R through the right channel
analog output amplifier 31R.
[0049]
Then, the analog audio signal of the left channel from the D / A converter 23L is supplied to the
addition unit 32R through the amplifier 33L for generating a sound leakage cancellation signal,
and is added to the analog audio signal of the right channel.
[0050]
Also, the analog audio signal of the right channel from the D / A converter 23R is supplied to the
addition unit 32L through the amplifier 33R for generating a sound leakage cancellation signal,
and is added to the analog audio signal of the left channel.
[0051]
At this time, as described above, when the sound leakage ratio of the left channel audio signal to
the right channel is 1 / ML, and the sound leakage ratio of the right channel audio signal to the
left channel is 1 / MR, The gain is 1 / ML (where ML> 1), and the gain of the amplifier 33R is 1 /
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MR (where MR> 1).
[0052]
As a result, the output signal CL of the amplifier 33L becomes the sound leakage cancellation
signal of the audio signal of the left channel leaking to the right channel, and the output signal
CR of the amplifier 33R the sound leakage cancellation of the audio signal of the right channel
leaking to the left channel It is made to be a signal.
[0053]
In this example, the gain of the amplifier 31L is 1-1 / MR so that the outputs of the adders 32L
and 32R have a gain of 1, and the gain of the amplifier 31R is 1-1 / R. It is considered as ML.
[0054]
As described above, the audio signal of the left channel and the audio signal of the right channel
to which the sound leakage cancellation signals are respectively added are output from the
adders 32L and 32R via the resistors 27L and 27R respectively. 28L and right channel audio
signal output terminal 28R.
[0055]
As a result of being configured as described above, in the first embodiment, as described below,
the sound leakage signal between the left and right channels is canceled by the sound leakage
elimination signals CL and CR, so that the sound leakage is generated. Is reduced.
[0056]
That is, also in FIG. 1, the large-amplitude audio signal of the left channel output from the left
channel audio signal output terminal 28L passes through the headphone unit 10L for the left
channel as in the case of FIG. It reaches the common connection point 13C connected to the
terminal 4C and flows to the common ground terminal 28C.
[0057]
And since the common connection point 13C is also connected to the headphone unit 10R for the
right channel, the large amplitude audio signal of the left channel is combined with the
headphone unit 10R for the right channel due to the presence of the common line resistance 14
and the like. It also leaks and is supplied.
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14
[0058]
However, in the first embodiment, as shown in FIG. 1, the sound leakage cancel signal CL
corresponding to the leakage of the left channel audio signal to the right channel through the
amplifier 33L is the audio of the right channel in the adding unit 32R. It is added to the signal.
In FIG. 1, since the audio signal of the right channel is not present (is zero), the adding portion
32R outputs the sound leakage cancellation signal CL supplied through the amplifier 33L, and
the sound leakage cancellation signal CL is It is supplied to the right channel headphone unit 10R
through the right channel audio signal output terminal 28R.
[0059]
As a result, in the right channel headphone unit 10R, the signal component leaking from the left
channel side via the common connection point 13C and the sound leakage cancellation signal CL
cancel each other out and are canceled, and from the right channel headphone unit 10R No
sound waves are generated or reduced by the sound leak signal.
[0060]
As described above, FIG. 1 describes the case where the left channel audio signal leaks to the
right channel, but when the right channel audio signal leaks to the left channel, the amplifier 33R
added to the adding unit 32L is used. The leakage is canceled and canceled in the left channel
headphone unit 10L by the sound leakage cancellation signal CR, and no sound wave is
generated or mitigated from the right channel headphone unit 10R. .
[0061]
As a result, it is possible to more accurately convey to the user the information originally
possessed by the left and right channel audio signals to the headphone user, and so-called
separation between channels is improved.
[0062]
Further, in the above embodiment, since the user can select whether or not to use the sound
leakage cancellation signal addition unit 30, a connection plug other than the connection plug of
the headphone 100 is connected to the headphone jack 28. For example, when the audio signal
output from the head jack 28 is reproduced by two external speakers or the audio signal output
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from the head jack 28 is sent to another audio device, the sound leakage cancellation signal is
added. It is possible to output the original left and right channel audio signals.
[0063]
In the above-described embodiment, the values of the sound leakage ratios 1 / ML and 1 / MR
are set to the headphone 100 for the output audio signal of the music player 300, for example,
when it is assumed that the music player 300 is attached with the headphone 100. Measure the
sound leakage ratio 1 / ML and 1 / MR when listening to the music, and set the measured sound
leakage ratio 1 / ML and 1 / MR in the amplifiers 33L, 33R, 31L and 31R in a fixed manner. You
can do it.
[0064]
However, in consideration of the fact that the characteristics of the music player 300 and the
characteristics of the headphones 100 may not all be the same, and the user may not use only
the headphones 100 attached to the music player 300, etc. When the values of / ML and 1 / MR
are fixedly set, there is a risk that the desired effect can not be obtained as a sound leakage
elimination effect.
In consideration of that, the control unit 301 controls the gains of the variable gain amplifiers
33L and 33R by the gain adjustment input of the user through the operation input unit 302,
using the amplifiers 33L and 33R as the configuration of the variable gain amplifier. It is good to
be configured to be able to.
[0065]
That is, in this case, the music player 300 is provided with a setting mode of the sound leakage
ratio, and for example, the first test signal in which the left channel audio signal is a large
amplitude signal and the right channel audio signal is zero is conversely It is recommended that
the music player 300 be provided with a test signal for outputting a second test signal of which
the right channel audio signal is a large amplitude signal and the left channel audio signal is zero
each for a predetermined time. .
[0066]
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16
The user selects the setting mode of the sound leakage ratio and reproduces the first test signal
and the second test signal described above with the music player 300, and while confirming the
sound leakage in the headphones being used at that time. The operation input unit 302 is used to
adjust the gains of the variable gain amplifiers 33L and 33R.
Thus, an appropriate value corresponding to the sound leakage ratio can be set as the gain of the
variable gain amplifiers 33L and 33R.
[0067]
In the embodiment of FIG. 1, the gains of the amplifiers 31L and 31R are adjusted so that the
gain of the output signal does not change even if the sound leakage cancellation signal is added
to the audio signals of the left and right channels. In the case of analog audio signals, the gains of
these amplifiers 31L and 31R may be fixed at 1 without adjusting the gains of the amplifiers 31L
and 31R.
[0068]
Second Embodiment The first embodiment is an example in which a sound leakage cancellation
signal is added to each channel audio signal at the stage of an analog audio signal.
However, when an analog element or circuit is used, the characteristic may not be stable due to
the variation of the element.
In addition, in the case of using an analog element, there are problems such as an increase in
component cost, circuit scale, and power consumption.
[0069]
In the second embodiment, in consideration of this point, when the audio signal is a digital signal,
the sound leakage cancellation signal is added to the audio data of each channel by digital
processing.
[0070]
FIG. 3 is a block diagram showing a configuration example of the music player 300 in the case of
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17
the second embodiment, and the same reference numerals are given to the same components as
the music player in the case of the first embodiment shown in FIG. Is attached.
[0071]
In the second embodiment, as shown in FIG. 3, the switch circuit 29 switched between when the
sound leakage countermeasure processing for the left and right channels is performed and when
the sound leakage countermeasure processing is not performed is the music data decoding unit
22. And the D / A converters 23L and 23R.
[0072]
Then, in the second embodiment, when the user does not perform the sound leakage
countermeasure processing through the operation input unit 302 and the selection operation
input is performed, the control unit 301 sets the switch circuit 29 as the switching control signal
SW in FIG. A control signal for switching to the switching state is supplied to the switch circuit
29.
[0073]
Then, at this time, the digital audio data DL and DR of the left and right two channels from the
music data decoding unit 22 are respectively supplied to the D / A converter 23L and the D / A
converter 23R through the switch circuit 29, and analog audio It is converted to a signal.
The left and right two-channel analog audio signals from the D / A converter 23L and the D / A
converter 23R pass through the analog amplifier 25L and the analog amplifier 25R, respectively,
and through the resistors 27L and 27R, respectively. The signal output terminal 28L and the
right channel audio signal output terminal 28R are respectively supplied.
[0074]
In addition, when the user performs a sound leakage countermeasure process through the
operation input unit 302 and performs selection operation input, the control unit 301 switches
the switch circuit 28 to a state opposite to the switching state of FIG. 3 as the switching control
signal SW. Control signal is supplied to the switch circuit 28.
[0075]
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Then, at this time, the digital audio data DL and DR of the left and right two channels from the
music data decoding unit 22 are supplied to the sound leakage cancellation signal addition unit
40 of digital signal processing.
As described later, the sound leakage cancellation signal addition unit 40 adds a signal for
canceling the sound leakage between the left and right channels to the left channel audio signal
and the right channel audio signal at the stage of the digital signal as described later. I do.
[0076]
In the second embodiment, in the sound leakage cancellation signal addition unit 40, the sound
leakage ratios 1 / ML and 1 / MR can be adjusted by the user operation input through the
operation input unit 302. Control unit 301 generates adjustment control signals CTL of sound
leakage ratios 1 / ML and 1 / MR according to the user operation input through operation input
unit 302, and generates the generated adjustment control signals CTL as sound leakage
cancellation signal addition unit 40. Configured to supply
[0077]
Then, the left and right two-channel digital audio signals DOL and DOR to which the sound
leakage cancellation signals are added from the sound leakage cancellation signal addition unit
40 are supplied to the D / A converter 23L and the D / A converter 23R, respectively. Are
converted to analog audio signals.
The left and right two-channel analog audio signals from the D / A converter 23L and the D / A
converter 23R pass through the analog amplifier 25L and the analog amplifier 25R, respectively,
and through the resistors 27L and 27R, respectively. The signal output terminal 28L and the
right channel audio signal output terminal 28R are respectively supplied.
[0078]
Next, FIG. 4 illustrates that in the second embodiment, the sound leakage is canceled and reduced
in a state where the connection plug 101 of the headphone 100 is inserted into the headphone
jack 28 of the music player 300. It is an equivalent connection circuit diagram for.
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19
[0079]
In this FIG. 4, as in the case of FIG. 1, even if it is assumed that the left channel audio signal is a
large amplitude signal and the right channel is completely silent, the right channel of the left
channel audio signal is It shows how the sound leakage to the sound is canceled and reduced.
[0080]
A detailed configuration example of the sound leakage cancellation signal addition unit 40 in the
music player 300 according to the second embodiment is as shown in FIG.
The sound leakage cancellation signal addition unit 40 in the second embodiment is a
configuration of a digital signal processing circuit.
[0081]
That is, in the sound leakage cancellation signal addition unit 40 in this embodiment, the digital
audio signal DL of the left channel from the music data decoding unit 22 is supplied to the
addition unit 42L through the coefficient multiplication unit 41L for sound leakage ratio
adjustment. At the same time, the digital audio signal DR of the right channel from the music data
decoding unit 22 is supplied to the addition unit 42R through the coefficient multiplication unit
41R for adjusting the sound leakage ratio.
[0082]
Then, the left channel digital audio signal DL from the music data decoding unit 22 is supplied to
the addition unit 42R through the coefficient multiplication unit 43L for generating a sound
leakage cancellation signal, and is added to the right channel digital audio signal.
[0083]
The right channel digital audio signal DR from the music data decoding unit 22 is supplied to the
addition unit 42L through the coefficient multiplication unit 43R for generating a sound leakage
cancellation signal, and is added to the left channel digital audio signal.
[0084]
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20
At this time, as described above, assuming that the sound leakage ratio of the left channel audio
signal to the right channel is 1 / ML, and the sound leakage ratio of the right channel audio
signal to the left channel is 1 / MR, the coefficient multiplication unit The coefficient to be
multiplied by 43L is 1 / ML (where ML> 1), and the coefficient to be multiplied by the coefficient
multiplier 43R is 1 / MR (where MR> 1).
As described above, the coefficients 1 / ML and 1 / MR are made variable by the adjustment
control signal CTL from the control unit 301.
[0085]
As a result, the output signal DCL of the coefficient multiplying unit 43L becomes a sound
leakage cancellation signal of the audio signal of the left channel leaking to the right channel,
and the output signal DCR of the coefficient multiplying unit 43R is an audio signal of the right
channel leaking to the left channel Sound leakage cancellation signal.
[0086]
Then, in the second embodiment, in order to prevent overflow in the digital domain by addition
in the adding unit 42L and the adding unit 42R, the coefficient to be multiplied by the coefficient
multiplying unit 41L is set to 1-1 / MR, The coefficient to be multiplied by the coefficient
multiplying unit 41R is set to 1-1 / ML.
[0087]
Here, as described above, the coefficients 1 / ML and 1 / MR are made variable by the
adjustment control signal CTL from the control unit 301.
[0088]
As described above, the digital audio signal DOL for the left channel and the digital audio signal
DOR for the right channel to which the sound leakage cancellation signals are respectively added
are output from the adding unit 42L and the adding unit 42R respectively to the D / A converters
23L and 23R. , And converted to an analog audio signal.
Then, analog audio signals of the left and right channels after conversion are supplied to the left
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21
channel audio signal output terminal 28L and the right channel audio signal output terminal 28R
through the resistors 27L and 27R, respectively.
[0089]
As a result, in the same manner as in the first embodiment, in the right channel headphone unit
10R, the signal component leaking from the left channel side via the common connection point
13C and the sound leakage cancellation signal CL mutually The cancellation and cancellation are
performed, and no sound wave is generated or reduced by the sound leakage signal from the
right channel headphone unit 10R.
[0090]
FIG. 4 illustrates the case where the left channel audio signal leaks to the right channel, but when
the right channel audio signal leaks to the left channel, the sound leakage from the coefficient
multiplying unit 43R added to the adding unit 42L The leakage is canceled and canceled in the
left channel headphone unit 10L by the cancellation signal DCR, and no sound wave is generated
or reduced from the sound leakage signal from the right channel headphone unit 10R.
[0091]
FIG. 5 shows a more detailed configuration example of the sound leakage cancellation signal
addition unit 40 of FIG.
As shown in FIG. 5, the sound leakage cancellation signal addition unit 40 is a configuration of a
digital product-sum operation unit.
[0092]
As shown in FIG. 5, in the sound leakage cancellation signal addition unit 40 of this example, the
digital audio signal DL of the left channel and the digital audio signal DR of the right channel
from the music data decode unit 22 are input to the input buffer registers 44L and 44R. One
sample is taken at a time.
Then, each time new digital audio sample data is taken into input buffer registers 44L and 44R,
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22
previous data is discarded from the input buffer registers 44L and 44R.
[0093]
Then, the sample data of the left channel fetched into the input buffer register 44L are
respectively supplied to the multipliers 45L and 47L, and the coefficient values stored in the
coefficient register 46L and the coefficient register 48L respectively multiply the respective
sample data. Be done.
[0094]
Here, the multiplier 45L and the coefficient register 46L constitute the coefficient multiplier 41L
of FIG. 4, and the multiplier 47L and the coefficient register 48L constitute the coefficient
multiplier 43L of FIG. In 46L, 1-1 / ML is stored as a coefficient value, and in the coefficient
register 48L, the sound leakage ratio 1 / ML is stored as a coefficient value.
[0095]
In this example, the coefficient values of the coefficient registers 46 L and 48 L are varied by the
adjustment control signal CTL from the control unit 301.
Alternatively, the control unit 301 generates a coefficient value corresponding to the user's
sound leakage ratio adjustment operation input, and supplies the generated value to the
coefficient registers 46L and 48L as the coefficient value.
[0096]
Then, the multiplication output from the multiplication unit 45L is supplied to the addition unit
42L of the left channel.
The multiplication output from the multiplication unit 47L is supplied to the addition unit 42R of
the right channel.
[0097]
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Similarly, the sample data of the right channel fetched into the input buffer register 44R is
respectively supplied to the multipliers 45R and 47R, and the coefficient values stored in the
coefficient register 46R and the coefficient register 48R are the respective sample data.
Multiplied by
[0098]
Here, the coefficient multiplication unit 41R of FIG. 4 is configured by the multiplication unit 45R
and the coefficient register 46R, and the coefficient multiplication unit 43R of FIG. 4 is
configured by the multiplication unit 47R and the coefficient register 48R. In 46R, 1-1 / MR is
stored as a coefficient value, and in the coefficient register 48R, the sound leakage ratio 1 / MR is
stored as a coefficient value.
[0099]
In this example, the coefficient values of the coefficient registers 46R and 48R are varied by the
adjustment control signal CTL from the control unit 301.
Alternatively, the control unit 301 generates a coefficient value corresponding to the adjustment
operation input of the sound leakage ratio of the user, and supplies the generated value to the
coefficient registers 46R and 48R as the coefficient value.
[0100]
Then, the multiplication output from the multiplication unit 45R is supplied to the addition unit
42R of the right channel.
The multiplication output from the multiplication unit 47R is supplied to the addition unit 42L of
the left channel.
[0101]
From the above, the left and right channels of digital audio signals DOL and DOR to which the
sound leakage cancellation signals are added are obtained from the adding sections 42L and
42R, respectively, and as shown in FIG. And the D / A converter 23R to convert it into an analog
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audio signal.
[0102]
The method of determining the coefficients to be set in the coefficient registers 46L, 46R, 48L
and 48R is the same as the method described in the first embodiment described above, and the
first and second coefficient setting modes are provided. It is possible to carry out by adjusting
and setting the coefficient to an optimal value so as to minimize the sound leakage by using the
test signal of.
[0103]
Although the example of FIG. 5 is a case where the sound leakage cancellation signal addition
unit 40 which is a digital signal processing unit is configured as a hardware including a productsum operation unit, the sound leakage cancellation signal addition unit 40 decodes music data
The digital audio data DL and DR from the unit 22 can also be executed as software processing
while acquiring one sample at a time.
[0104]
FIG. 6 is a flow chart showing the processing procedure in the case of such software processing.
In this case, the processing of each step in FIG. 6 is executed by the microcomputer of the control
unit 301 of FIG.
[0105]
That is, first, the control unit 301 takes in the digital audio signals DL and DR of the left and right
channels from the audio data decoding unit 22 as input sample data (step S101).
Next, the control unit 301 reads the coefficients 1 / ML, 1 / MR, 1-1 / ML, and 1-1 / MR stored
in coefficient registers (not shown) (step S102).
[0106]
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Then, next, the control unit 301 is: DOL = DL × (1-1 / MR) + DR × 1 / MR DOR = DR × (1-1 /
ML) + DL × 1 / ML (Expression A) The product-sum operation processing represented is
executed (step S103).
[0107]
Next, the control unit 301 supplies the digital signals DOL and DOR obtained in step S103 to the
D / A converter 23L and the D / A converter 23R to convert them into analog audio signals and
output them. (Step S104).
[0108]
Then, the control unit 301 determines whether or not to end the audio output based on whether
or not the music data of the music content from the music content storage unit 21 has ended,
and whether or not the user has issued a reproduction stop instruction. (Step S105) If it is
determined that the audio output has not ended yet, the process returns to step S101, and the
processing after step S101 is repeated.
When it is determined in step S104 that the audio output is to be ended, the processing routine
of FIG. 6 is ended.
[0109]
The coefficients 1 / ML, 1 / MR, 1-1 / ML, and 1-1 / MR set in the coefficient register are used by
the first and second test signals described in the first embodiment. Are set by the user in
advance.
[0110]
When software processing such as that described above is performed, there is an advantage that
the hardware for performing the product-sum operation of (Expression A) described above
becomes unnecessary.
[0111]
Third Embodiment In the second embodiment described above, the sound leakage amount can be
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adjusted so that the user can adjust and set the music player 300 according to the headphones to
be attached. The magnitude of the leakage cancellation signal can be set optimally.
However, in the above embodiment, the phase of the sound leakage cancellation signal is not
considered.
That is, when the phases of the sound leakage cancellation signal and the audio signal of the
channel to be erased do not match in each of the headphone units 10L and 10R, a good
cancellation effect may not be obtained.
[0112]
The third embodiment is a case where the phase of the sound leakage cancellation signal can be
adjusted by the user.
[0113]
The method of adjusting the phase of the sound leakage cancellation signal can also be applied to
the case where the sound leakage cancellation signal addition unit 30 is provided at the stage of
the analog audio signal described in the first embodiment.
That is, in the sound leakage cancellation signal addition unit 30 of FIG. 1, variable delay means
of an analog circuit, for example, a phase shift circuit is provided on the input side or the output
side of the amplifier 33L and the input side and the output side of the amplifier 33R. good.
[0114]
However, accurate phase adjustment in analog circuits is quite difficult.
Therefore, in the third embodiment, a phase adjustment unit is provided in the sound leakage
cancellation signal addition unit 40 at the stage of the digital audio signal of the second
embodiment.
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In this case, phase adjustment is performed in units of samples of digital audio data.
[0115]
FIG. 7 is a block diagram showing a configuration example of the sound leakage cancellation
signal addition unit 40 in the case of the third embodiment.
In the example of FIG. 7, n stages (n is an integer of 2 or more) of shift registers 440L and 440R
are provided instead of the input buffer registers 44L and 44R of the example of FIG.
The n-stage shift registers 440L and 440R output digital data delayed by 0, 1, 2,..., N-1 samples
with respect to the input digital data as the output of each stage.
[0116]
In the example of FIG. 7, the first stage outputs L [n-1] and R [n-1] of the shift registers 440L and
440R are the input digital data itself, and the output L [i], R [i] of the i-th stage. The smaller the
value of i, the larger the delay amount, and the outputs L [0] and R [0] are data samples delayed
by n-1 samples than the input digital data.
[0117]
The first stage outputs L [n-1] and R [n-1] of the shift registers 440L and 440R are respectively
supplied to the multipliers 45L and 45R, and are stored in the coefficient registers 46L and 46R,
respectively. It is multiplied by ML and 1-1 / MR.
The multiplication results of the multipliers 45L and 45R are respectively supplied to the adders
42L and 42R.
[0118]
On the other hand, with respect to the register output of each stage of shift registers 440L and
440R, multiplication units 47L [0], 47L [1], 47L [2],..., 47L [N-1] and multiplication units 47R [0]
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, 47R [1], 47R [2],..., 47R [N-1] are provided.
[0119]
In each of multiplication units 47L [0], 47L [1], 47L [2],..., 47L [N-1] for the left channel, the
coefficient 1 / ML stored in the coefficient register 48L And the register output of each stage are
multiplied, and the multiplication result is supplied to the selector 49L.
The selection control signal SELL is supplied from the control unit 301 to the selector 49L in
accordance with the operation input through the operation input unit 302 by the user.
From the selector 49L, one of the multiplication results selected by the selection control signal
SELL out of the multiplication results of the multiplication units 47L [0], 47L [1], 47L [2], ..., 47L
[N-1]. Is obtained, and the selected single multiplication result is supplied to the addition unit
42R with the right channel signal.
[0120]
In addition, in each of multiplication units 47R [0], 47R [1], 47R [2], ..., 47R [N-1] for the right
channel, the coefficient 1 / MR stored in the coefficient register 48R And the register output of
each stage are multiplied, and the multiplication result is supplied to the selector 49R.
The selection control signal SELR is supplied from the control unit 301 to the selector 49R in
accordance with the operation input through the operation input unit 302 of the user.
From the selector 49R, one of the multiplication results selected by the selection control signal
SELR among the multiplication results of the multiplication units 47R [0], 47R [1], 47R [2], ...,
47R [N-1]. Is obtained, and the selected single multiplication result is supplied to the addition
unit 42L with the left channel signal.
[0121]
In the music player 300 of the third embodiment in which the sound leakage cancellation signal
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addition unit 40 is configured as described above, setting modes of coefficients and phases are
provided, and the first test signal and the second test signal as described above are provided.
Coefficients 1 / ML, 1 / MR, 1-1 / ML, 1-1 / MR setting and phase adjustment are performed
using a test signal.
[0122]
That is, the user puts the music player 300 in the coefficient and phase setting mode, and
reproduces, for example, the first test signal at first.
Then, in a state where the first test signal is being reproduced, the coefficient 1 / ML is set so
that the amount of sound leakage of the left channel signal to the right channel is minimized.
At this time, the coefficient supplied to the multiplication unit 45L is set to a value such that the
multiplication result does not overflow.
[0123]
Then, the coefficient 1 / ML set as described above is stored in the coefficient register 48L.
Also, the coefficient 1-1 / ML is calculated, and the calculation result is stored in the coefficient
register 46R.
[0124]
Next, the first test signal is continuously reproduced, and the selection control signal SELL to the
selector 49L is adjusted so that the amount of sound leakage of the left channel signal to the
right channel is minimized.
Then, the selection control signal SELL as the adjustment result is held as the selection control
signal SELL of the selector 49L.
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30
[0125]
Next, the test signal to be reproduced is changed to the second test signal, and the same as above
is performed for the right channel.
That is, in a state where the second test signal is being reproduced, the coefficient 1 / MR is set
such that the sound leakage amount of the right channel signal to the left channel is minimized.
At this time, the coefficient supplied to the multiplication unit 45R is set to a value such that the
multiplication result does not overflow.
[0126]
Then, the coefficient 1 / MR set as described above is stored in the coefficient register 48R.
Also, the coefficient 1-1 / MR is calculated, and the calculation result is stored in the coefficient
register 46L.
[0127]
Next, the second test signal is continuously reproduced, and the selection control signal SELR to
the selector 49R is adjusted so that the amount of sound leakage of the right channel signal to
the left channel is minimized.
Then, the selection control signal SELR as the adjustment result is held as the selection control
signal SELR of the selector 49R.
[0128]
In the third embodiment, since the phase of the sound leakage cancellation signal can be
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adjusted, further improvement of the sound leakage cancellation effect can be expected.
[0129]
[Other Embodiments or Modifications] In the above-described embodiment, the sound leakage
reduction method has been described by taking the case of stereo audio signals of left and right
two channels as an example, but the first channel audio signal and the second channel audio
signal It goes without saying that the present invention is not limited to the left channel signal
and the right channel signal of the stereo audio signal.
[0130]
Although the audio signal output device is a music player, the present invention is not limited to
a music player, and any device having an audio signal output terminal having a three-pole
terminal configuration is applicable to the present invention. Needless to say.
[0131]
FIG. 1 is a circuit diagram for describing a first embodiment of a sound leakage reduction method
according to the present invention.
It is a block diagram showing an example of composition of a music player of an example of a
device by which a 1st embodiment of a sound leak reduction method by this invention was
applied.
It is a block diagram which shows the structural example of the music player of the example of
the apparatus to which the 2nd Embodiment of the sound leakage reduction method by this
invention was applied.
It is a circuit diagram for describing a second embodiment of the sound leakage reduction
method according to the present invention.
It is a block diagram which shows the structural example for implement | achieving 2nd
Embodiment of the sound leakage reduction method by this invention.
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It is a flowchart which shows the structural example for implement | achieving 2nd Embodiment
of the sound leakage reduction method by this invention.
It is a block diagram showing an example of composition for realizing a 3rd embodiment of a
sound leak reduction method by this invention.
It is a figure for demonstrating the apparatus provided with 3 pole terminal.
It is a figure for demonstrating the sound leak between channels in, when using a 3-pole
terminal.
It is a figure for demonstrating the apparatus using 4 pole terminal in order to reduce a sound
leak.
It is a figure for demonstrating the sound leak reduction between channels in, when using 4 pole
terminal.
Explanation of sign
[0132]
28 ... headphone jack, 28 L ... left channel audio signal output terminal, 28 R ... right channel
audio signal output terminal, 28 C ... common ground terminal, 30 ... sound leakage cancellation
signal addition unit (for analog processing) 40 ... sound leakage cancellation signal Adder (for
digital processing)
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33
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