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JP2013142735

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DESCRIPTION JP2013142735
Abstract: The present invention provides a noise cancellation headphone capable of achieving
both improvement in sound quality and improvement in noise cancellation performance.
SOLUTION: A first driver unit 1 for reproducing a low range, another driver unit 2 for
reproducing a range other than the low range, and a musical tone signal are divided into the low
range and the other range. From the crossover circuit 3 for inputting the musical tone signal of
the tone range to the first driver unit 1 and the tone signal of the tone range other than the low
tone range to another driver unit 2 and noise signals of all frequency bands that can be detected
by the microphone 6 And a noise cancel circuit 4 that generates a cancel signal and inputs the
generated cancel signal to the first driver unit 1. [Selected figure] Figure 1
ノイズキャンセルヘッドホン
[0001]
The present invention relates to a noise cancellation headphone provided with a plurality of
driver units. The "headphones" according to the present invention includes stereo headphones
worn on the left and right ears and monaural headphones worn on only one ear. Further, it is not
limited by types, including an ear-cover type covering the ear from the outside, an ear-loading
type to be put on the ear, an inner-ear type to be inserted into the ear, and an ear-hook type to be
put on the ear. Therefore, what is called "earphones" is also included in the "headphones" in the
present specification and the like. In the present specification and the like, “driver unit” is
generally referred to as a speaker unit, which converts an electric signal into sound and emits the
sound.
09-05-2019
1
[0002]
Most conventional noise cancellation headphones invert the phase of the external noise signal
converted by the microphone to form a cancellation signal, add this cancellation signal and the
tone signal from the sound source, and input it to one driver unit. It is configured. Therefore, the
driver unit reproduces the sound of the musical tone signal and the cancel signal, the reproduced
sound of the cancel signal and the external noise are canceled each other, and the headphone
user can hear only the reproduced sound of the musical tone signal.
[0003]
According to the above-mentioned conventional noise cancellation headphone, since a signal
obtained by combining the musical tone signal and the cancel signal is input to one driver unit,
the musical tone signal and the cancel signal affect each other. Therefore, the noise cancellation
performance is sacrificed when the sound quality is emphasized, and the sound quality tends to
be sacrificed when the noise cancellation performance is emphasized. Therefore, technology has
been developed to realize both sound quality and noise cancellation performance at high levels.
However, since the principle of combining a musical tone signal and a cancellation signal to drive
one driver unit, both sound quality and noise cancellation performance have to be compromised,
and there is a limit to improving both performances. .
[0004]
In addition, the noise cancellation signal includes the low to mid range and further to the high
range, and all these ranges, especially the mid to high range noise, are also noises when it is tried
to cancel this. It also adversely affects cancellation performance. That is, since the wavelength of
voice becomes short in the middle and high tone range, the noise signal is generated depending
on the time and filter characteristics required for noise cancellation processing such as
generation of cancellation signal by phase inversion processing of noise signal and addition of
cancellation signal and musical tone signal. The phase of the cancellation signal may be deviated
from the phase that should be originally with respect to the phase of (1), and noise may be
amplified at a certain frequency.
[0005]
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2
FIG. 3 shows an example of the noise cancellation characteristic of the conventional noise
cancellation headphone. The horizontal axis represents frequency, and the vertical axis
represents noise cancellation amount by sound pressure. In addition, a noise signal detected by
the microphone is directly phase-inverted as a cancel signal without providing a low-pass filter
described later. Below 0 dB there is noise cancellation effect, and above 0 dB the noise increases.
As apparent from FIG. 3, the noise cancellation effect is high in the low frequency range.
However, it can be seen that in the middle and high range, the above-described phase shift
causes noise to peak at a specific frequency band and amplifies noise rather.
[0006]
Therefore, in the conventional noise cancellation headphone, the external noise signal converted
by the microphone is passed through a low pass filter, and only the bass component of the noise
signal is used as the cancellation signal. Most of the external noise is in the low frequency range,
so it is considered that the low frequency range alone is sufficient for practical use if there is a
noise cancellation effect. In this way, it is possible to eliminate the problem that noise is rather
amplified in the middle and high range. However, even in the noise canceling headphone
provided with the low pass filter, one driver unit is driven by the signal obtained by adding the
musical tone signal and the canceling signal. Therefore, as described above, the sound quality is
improved and the noise cancellation performance is improved. There is a limit to making it
compatible. In addition, since the characteristic of the low-pass filter is that the output signal is
delayed with respect to the input signal in time, the cancellation signal generated by passing the
external noise signal through the low-pass filter will also be delayed from the timing originally
required. As a result, the noise cancellation performance is adversely affected.
[0007]
By the way, in order to improve the sound quality of the headphones, a two-way system
headphone is known that includes a driver unit that reproduces a bass region and a driver unit
that reproduces a treble region (for example, Patent Document 1, Patent Document 2, Patent
Document 3). In addition to a driver unit for reproducing the low range and the high range, a 3way type headphone equipped with a driver unit for reproducing the mid range is also
commercially available. However, these two-way and three-way headphones are intended to
improve the sound quality by widening the reproduction frequency band and reproducing well
over the entire reproduction frequency band, and do not have a noise cancellation function.
09-05-2019
3
[0008]
In order to enable noise cancellation without loss of sound quality, in addition to a driver unit
driven by a tone signal, a piezoelectric element driven by a noise cancellation signal generated by
a noise signal from a microphone is provided. There has been proposed a headphone in which a
frame of a driver unit is coupled by the piezoelectric element (see Patent Document 4). According
to the invention described in Patent Document 4, since the piezoelectric element drives the frame
of the driver unit by external noise, the sound wave emitted from the driver unit is a combination
of the reproduced sound of the musical tone signal and the reproduced sound of the cancel
signal. The noise is canceled by the reproduction sound of the cancellation signal. Since the
electrical coupling between the noise cancellation signal and the tone signal is shallow, the
adverse effect of the noise cancellation signal on the tone signal can be reduced.
[0009]
In addition to a driver unit driven by a tone signal, a headphone provided with a driver unit for
noise cancellation driven by a cancellation signal generated by a noise signal from a microphone
has also been proposed (for example, Patent Document 5, Patent Document) 6). The headphone
described in Patent Document 5 includes a driver unit driven by a tone signal and a driver unit
for noise cancellation driven by a noise cancellation signal, and the external noise and the
cancellation sound emitted from the driver unit for cancellation The external space
communicates with the inside of the headphone so as to be acoustically coupled inside the
headphone.
[0010]
The headphone described in Patent Document 6 includes a driver unit driven by a tone signal
and a driver unit for noise cancellation driven by a noise cancellation signal, and the cancellation
driver unit emits a cancellation sound outward. , Noise around the headphones. The headphone
described in Patent Document 5 cancels noise within the headphone, whereas the headphone
described in Patent Document 6 has a difference in that noise outside the headphone cancels
noise around the headphone.
09-05-2019
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[0011]
Japanese Patent Publication No. 06-38552 Patent Document No. 2516904 Patent Document No.
4184283 Patent Document No. 2008-99127 Patent Document No. 2009-17485 Patent
Document No. No. 3153113
[0012]
So far, we have described the technological transition of headphones and noise-canceling
headphones, as well as technical issues.
In the transition of noise cancellation headphone technology, it is a major task to simultaneously
improve the sound quality or the reproduction performance and the noise cancellation
performance, and there is room for further improvement. That is, in order to improve the sound
quality or the reproduction performance, it is effective to make the driver unit a two-way system
or a three-way system multi-way system as described in Patent Documents 1 to 3. is there.
However, in such a multi-way system, noise cancellation is inconsistent.
[0013]
On the other hand, although the noise cancellation headphones described in Patent Documents 4
to 6 are provided with two driver units, one driver unit is dedicated to tone reproduction and the
other driver unit is dedicated to noise cancellation. Therefore, improvement in noise cancellation
performance can be expected. However, no special consideration is given to the improvement of
sound quality or reproduction performance.
[0014]
The present invention aims to solve the problems of the conventional noise cancellation
headphone described above, that is, to provide a noise cancellation headphone capable of
achieving both improvement in sound quality or reproduction performance and improvement in
noise cancellation performance. I assume.
[0015]
According to the present invention, a first driver unit for reproducing the low frequency range,
another driver unit for reproducing the low frequency range other than the low frequency range,
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5
and a musical tone signal divided into the low frequency range and the low frequency range A
cancellation signal is generated from a crossover circuit that inputs a musical tone signal to the
first driver unit and a musical tone signal of a range other than the low range to the other driver
unit, and a noise signal of all frequency bands that can be detected by the microphone. And a
noise cancellation circuit to be input to the first driver unit.
[0016]
The first driver unit reproduces the low frequency range, and the other driver unit configures
multi-way headphones that reproduce the frequency range other than the low frequency range to
obtain well-balanced high-quality reproduced sound over a wide frequency range. Can.
The cancellation signal generated by the noise cancellation circuit is generated from noise signals
of all frequency bands that can be detected by the microphone without passing through a low
pass filter or the like.
Therefore, although the cancellation signal includes middle and high range signals, the first
driver unit reproduces only the low range, and the middle and high range can not be reproduced,
or the sound pressure level is low even if it is. Therefore, even if there is a phase shift of the
cancellation signal with respect to the noise signal in the middle and high tone range, there is no
problem that the noise is amplified and reproduced. Since noise cancellation is performed only
by the first driver unit that reproduces only the low-pass band, there is no time delay of the lowpass noise cancellation signal by the low-pass filter, and good noise cancellation is possible.
While being able to acquire an effect, the influence which a noise cancellation function has on
tone reproduction performance can be reduced extremely.
[0017]
It is a block diagram showing the example of the noise cancellation headphone concerning the
present invention. It is a graph which shows the musical tone reproduction | regeneration
frequency characteristic in the Example of the noise cancellation headphone which concerns on
this invention. It is a graph which shows the example of the noise cancellation characteristic in
the conventional general noise cancellation headphone.
09-05-2019
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[0018]
Hereinafter, embodiments of the noise cancellation headphone according to the present
invention will be described with reference to the drawings.
[0019]
In the embodiment of the noise cancellation headphone according to the present invention, as
shown in FIG. 1, the first driver unit 1 for reproducing the low frequency band and the first
driver unit 1 separately reproduce the non-low frequency band. A second driver unit 2 is
provided.
The first driver unit 1 is a unit called "woofer" suitable for reproducing the low tone range, and
the second driver unit 2 is a unit called "tweeter" suitable for reproducing the middle and high
tones.
[0020]
The first driver unit 1 and the second driver unit 2 are incorporated in a common headphone
case (not shown). The mode of incorporating each of the driver units 1 and 2 into the headphone
casing is optional, and may be incorporated in a mode suitable for the type of headphones. In any
case, the sound waves reproduced by the driver units 1 and 2 can be merged to reach the
tympanic membrane of the user.
[0021]
A musical tone signal is input to the driver units 1 and 2 from the musical tone signal input
terminal 5. A compact disk (CD) player, an MP3 player, an IC recorder, and other appropriate
tone generators are connected to the tone signal input terminal 5, and tone signals are input
from the tone generator. The tone signal is raised to a power suitable for driving the headphones
by an amplifier on the sound source side. A crossover circuit 3 is provided behind the tone signal
input terminal 5 so that the two driver units 1 and 2 can be divided into tone ranges and driven
by the tone signal.
09-05-2019
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[0022]
The crossover circuit 3 divides the above-mentioned tone signal including the signal of the whole
range into the signal of the low range and the signal of the middle range and the high range as
shown in FIG. , Middle and high range signals are input to the second driver unit 2. As shown in
FIG. 2, a frequency fc at a position where a graph A representing the frequency characteristic of a
low frequency band signal and a graph B representing the frequency characteristic of a middle or
high frequency band signal intersect is called a crossover frequency. The crossover circuit 3 also
has the function of a network in a multi-way speaker system, and can adjust the balance between
the bass signal and the middle and treble signal to set the crossover frequency fc. .
[0023]
The low band signal is input to the first driver unit 1, and the middle and high band signals are
input to the second driver unit 2, but the noise cancel circuit 4 is connected to the drive circuit of
the first driver unit 1. The first driver unit 1 is also configured to receive a noise cancellation
signal. A microphone for detecting environmental noise is attached to the headphone casing, and
a noise signal that is detected by the microphone 6 and electroacoustically converted is input to
the noise cancellation circuit 4. The noise cancellation circuit 4 has a function of converting the
phase of the noise signal into an opposite phase to generate a cancellation signal. Further, the
noise cancellation circuit 4 has a function of an adder for adding the generated cancellation
signal and the signal of the above-mentioned bass range, and a signal obtained by adding the
cancellation signal and the musical tone signal of the bass range is inputted to the first driver
unit 1 It is configured to
[0024]
According to the embodiment of the noise cancellation headphone according to the present
invention described above, the first driver unit 1 reproduces a low frequency band, and the
second driver unit 2 constitutes a multi-way type headphone which reproduces a frequency band
other than the low frequency band. Because of this, it is possible to obtain well-balanced highquality reproduced sound over a wide frequency band. In particular, since the middle and high
tones are not affected by the noise canceling operation, it is possible to design and adjust purely
in pursuit of sound quality improvement.
09-05-2019
8
[0025]
The cancellation signal generated by the noise cancellation circuit 4 is generated as a signal of
the opposite phase based on the noise signal of the entire frequency band that can be detected
by the microphone 6 without passing through a low pass filter or the like. The cancellation signal
also includes middle and high range signals. Therefore, the cancellation signal also includes a
signal that amplifies noise due to a phase shift as described with reference to FIG. 3 in a specific
frequency band of middle and high tone.
[0026]
However, the first driver unit 1 reproduces only the bass region, can not reproduce the middle
and high tone regions, and the sound pressure level is low even if it is played Even if there is a
phase shift, there is no problem that the noise is amplified and reproduced. In addition, since the
type of low pass filter is not used and the noise cancellation is performed only by the first driver
unit 1 that reproduces only the low tone range, the noise cancellation function has extremely
little influence on the tone reproduction performance. it can.
[0027]
Therefore, according to the present invention, while improving the sound quality by using a
plurality of driver units, it is possible to minimize the adverse effect on the reproduction
performance in the middle to high frequency range accompanying the noise cancellation
operation.
[0028]
The embodiment shown in FIG. 1 is an example of a two-way system using two driver units, but a
three-way system using three driver units, or any other multi-way system may be used.
In the 3-way or more multi-way system, in addition to the "woofer" and "tweeter", a "squaker"
suitable for reproducing the midrange is used. In this case, the crossover circuit 3 separates the
musical tone signal into signals belonging to the low range, the mid range, and the high range,
and the signals belonging to the respective ranges are "woofer", "squaker", "tweeter". Distribute to
In any case, the noise cancellation signal is configured to be input only to the driver unit
09-05-2019
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responsible for the reproduction of the low frequency band.
[0029]
The invention can be applied to any type of headphones or earphones, regardless of the type of
headphones as mentioned earlier.
[0030]
1 first driver unit 2 second driver unit 3 crossover circuit 4 noise cancellation circuit 5 tone
signal input terminal 6 microphone
09-05-2019
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