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DESCRIPTION JP2003018689

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DESCRIPTION JP2003018689
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
sound reproducing apparatus used as a subwoofer in an environment with noise, such as a car.
[0002]
2. Description of the Related Art Heretofore, as a sound reproducing apparatus, one described in
Japanese Patent Application Laid-Open No. 61-112496 is known.
[0003]
FIG. 13 shows the structure of a conventional sound reproducing apparatus, which is attached in
the vicinity of the audio device 101 and the position of the occupant's ear such as a headrest, and
detects the noise in the cabin including the reproduced sound from the audio device 101. Noise
is detected by a noise detection circuit and noise signal detection circuit that delays the music
signal from the audio device 101 for a predetermined time while subtracting the music signal
delayed for a predetermined time from the detection signal of the microphone 102 and the audio
device 101 The control unit 104 is provided with a control unit 104 that incorporates a noise
control circuit that mixes a noise cancellation signal of the opposite phase obtained by inverting
the noise signal component with the music signal, amplifies the power, and reproduces it from
the speaker 103. It is configured to connect.
[0004]
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1
According to the above construction, a noise in the passenger compartment including the
reproduced sound of the audio device is detected at a position close to the ear of the passenger,
and a music signal component delayed for a predetermined time based on the passenger
compartment acoustic transfer characteristic from the detection signal of the microphone. To
detect the noise signal component, invert the noise signal component to create a noise
cancellation signal of opposite phase, mix the noise cancellation signal with the music signal, and
amplify and output from the speaker into the vehicle interior, the microphone Even if the
detection signal contains a music signal, no signal with opposite phase is output for the music
reproduction sound, so only the true noise is acoustically offset, and the noise in the car room is
increased even if the noise in the car increases. Since the noise is canceled out, the music
reproduction sound can be clearly heard even in the driving with high noise level.
In addition, cavity resonance noise of a vehicle known as booming noise can be suppressed to
reduce discomfort.
[0005]
In this sound reproducing apparatus, it is necessary to attach a microphone to the headrest
position in the vehicle compartment and to attach a dedicated control unit in the vicinity of the
audio apparatus. The various restrictions above will be imposed.
Therefore, it is very difficult to add this sound reproduction device after the vehicle is completed.
From the viewpoint of increasing the degree of freedom in designing a vehicle and reducing the
cost, it is also required to reduce restrictions on the vehicle side as much as possible.
[0006]
The present invention is intended to solve this problem, and it is possible to reduce noise at the
ear of an occupant of a vehicle or the like by means of an audio device, and also to easily retrofit
it to a completed vehicle. It is an object of the present invention to provide a sound reproduction
device with less restriction on the side.
[0007]
SUMMARY OF THE INVENTION In order to solve this problem, the invention according to claim 1
of the present invention acoustically separates the back and front of a speaker unit mounted
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inside, And a speaker box having a recess opened to the outer periphery, a microphone attached
so as to pick up ambient sound in the recess of the speaker box, the speaker unit and the
microphone are electrically connected, and detected by the microphone And an electric circuit
configured to output a sound based on the generated sound from the speaker unit, the electric
circuit including a music compensation circuit that receives a music signal, an output of a
microphone, and an output of the music compensation circuit. A noise signal processing circuit
having an input, a music signal processing circuit having a music signal as an input, a signal
having an output of the noise signal processing circuit and an output of the music signal
processing circuit as an input It consists of an arithmetic circuit and a power amplifier circuit
that drives the speaker unit with the output of the signal addition circuit as its input, and is
placed under the seat in the vehicle, etc., and has simple wiring similar to a conventional
subwoofer etc. Only by acoustically canceling out the noise in the cabin, and suppressing the
hollow resonance of the vehicle known as booming noise, it can reduce the unpleasant feeling
and it is difficult to touch the microphone directly, so we touched the thing Since the speaker
unit and the loop of the microphone are in close proximity to each other, it is difficult to receive
the contact sound at the time of operation, and it is possible to make stable and difficult to cause
abnormal control.
[0008]
According to a second aspect of the present invention, in the first aspect, the sound absorbing
material is inserted in the recess of the speaker box, and the microphone is configured to
resonate based on the structure of the recess. It has an effect of suppressing noise components
other than the frequency to be a noise reduction target from entering the microphone.
[0009]
According to a third aspect of the present invention, in the first aspect, the speaker unit includes
a printed circuit board on which the microphone and the electric circuit are mounted, and the
speaker box is mounted on the printed circuit board. It is configured to separate the back space
and the recess on the outside thereof, and the connector and the microphone are arranged in the
recess, and have the effect of being able to be easily assembled and inexpensively configured. .
[0010]
According to a fourth aspect of the present invention, there is provided an auxiliary unit for
mounting a microphone according to the first aspect, wherein the auxiliary unit is supported
outside the speaker box, and the microphone and the noise signal are provided. The processing
circuit is configured to be connected via the connector, and the auxiliary unit is retrofitted to the
speaker box having the same shape as that of the conventional sound reproducing apparatus
such as a subwoofer, and the sound reproduction with the muffling function is provided. It has
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the effect that the device can be configured.
[0011]
According to a fifth aspect of the present invention, in the invention according to the first aspect,
the microphone is a first microphone, and a second microphone attached to the back surface
space of the speaker unit of the speaker box; An acoustic feedback control circuit that receives
the output of the second microphone, and a signal addition circuit that receives the output of the
noise signal processing circuit, the output of the music signal processing circuit, and the output
of the acoustic feedback control circuit It has the effect of being able to be compatible with
acoustic feedback control applied to a subwoofer or the like.
[0012]
According to a sixth aspect of the present invention, in the fifth aspect, the music compensation
circuit is configured to receive the output of the second microphone mounted in the space
behind the speaker unit. It has the effect of enhancing the independence of the music
reproduction and the muffling operation by making the input signal of the music compensation
circuit closer to the acoustic music reproduction signal and facilitating the signal processing with
high accuracy.
[0013]
The invention according to claim 7 of the present invention is the invention according to claim 1,
wherein position recognition means for recognizing a specified position in the acoustic space and
noise signal processing using the output of the position recognition means as an input It has a
fail-safe circuit that controls the output of the circuit, and it can be moved easily because it is
easy to install, and when it is moved from the placement position where the silencing effect is
high, the mute signal is not output. Function to prevent erroneous mute control.
[0014]
According to an eighth aspect of the present invention, in the seventh aspect, the position
recognition means is configured to input the output of the music compensation circuit, the
output of the microphone, and the vehicle speed signal. It has the effect that position recognition
means can be provided only by circuit processing without structural changes.
[0015]
The invention according to claim 9 of the present invention is, in the invention according to claim
1, constituted so as to have adjusting means for changing the characteristics of the noise signal
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processing circuit, and for a plurality of applications. On the other hand, it has the effect that it
can be adapted.
[0016]
According to a tenth aspect of the present invention, in the first aspect, the noise signal
processing circuit is constituted by a digital signal processing circuit and the characteristic is
changed by software. There is an effect that it can be easily adapted by a computer etc. to a
plurality of applications and it is easy to construct a system etc. adapted automatically.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be
described below with reference to FIGS. 1 to 12. FIG.
[0018]
Embodiment 1 FIG. 1 shows the structure of a sound reproducing apparatus according to a first
embodiment of the present invention.
8a is a recessed part which exists inside from an outer peripheral surface.
The recess 8a is connected to the external space by the opening 8b.
The opening 8b is preferably sized so as to allow air to pass but not human fingers or the like,
and may be covered with a mesh so as to prevent dust and the like from entering.
Alternatively, a bracket or the like may be attached to the outside of the outer peripheral surface,
and a gap may be provided in the mounting portion of the microphone 1 to provide a recess in
which a hand etc. can not enter directly from the outside.
The microphone 1 is attached to the recess 8a.
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In order to draw the signal of the microphone 1 into the back space of the speaker unit 7, a
through hole may be provided between the recess 8 a and the speaker internal space, and the
microphone 1 may be attached.
At this time, in order to maintain the acoustic separation structure between the back surface and
the front surface of the speaker unit 7 in the speaker box 8, an airtight member or the like is
used so that the sealing property between the microphone 1 and the mounting wall of the recess
8a can be taken. Good.
[0019]
FIG. 2 shows the configuration of the electric circuit of the sound reproducing apparatus
according to the first embodiment of the present invention. In FIG. 2, 1 is a microphone and 2 is
a music signal output from the audio apparatus. A music compensation circuit comprising a band
pass filter circuit and a phase shift circuit for causing a music reproduction sound output from
the sound reproduction apparatus according to the present invention to be equal to a signal
returned to the microphone 1 again. .
A noise signal processing circuit 3 receives the output of the microphone 1 and the output of the
music compensation circuit 2 and subtracts the output signal of the music compensation circuit
2 from the output signal of the microphone 1 as a noise reduction target. The filter circuit is
configured to convert the noise signal so that the reproduced sound at the muffling point is in
reverse phase with respect to the noise.
In the case of the sound reproduction apparatus according to the present invention, this filter
circuit does not necessarily output a signal of the opposite phase, since it is conceivable that the
microphone and the muffling point are separated.
Moreover, in order to suppress an excessive signal generated when something collides with a
microphone etc., the compressor circuit which suppresses an amplification factor with respect to
an excessive input so that a signal may not be distorted, and the signal which exceeded the
dynamic range are cut. It may include a limiter circuit and the like.
A music signal processing circuit 4 is a circuit for converting a music signal from an audio device
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into a signal suitable for music reproduction as a part of a normal audio device, and a band pass
filter circuit or the like is generally used.
A signal addition circuit 5 is composed of an addition circuit that electrically adds the output
signal of the noise signal processing circuit 3 and the output signal of the music signal
processing circuit 4. Reference numeral 6 denotes a power amplification circuit, which amplifies
the power of the output of the signal addition circuit 5. A speaker unit 7 is driven by the power
amplification circuit 6. A speaker box 8 is configured to acoustically separate the front surface
and the back surface of the speaker unit 7 by attaching the speaker unit 7. For example, an
airtight member may be sandwiched between the speaker unit 7 and the speaker box 8 Good.
Thus, an acoustically separated speaker internal space is configured. Moreover, the microphone
1 is attached to the outer side of this speaker internal space, for example, the outer wall surface
of the speaker box 8. This makes it possible to easily receive extraneous noise signals.
[0020]
Next, these operations will be described. First, when a music signal is input from an audio device
in an acoustic space free from extraneous noise, the music signal is input to the music signal
processing circuit 4 and the music compensation circuit 2. The signal that has passed through
the music signal processing circuit 4 passes through the signal addition circuit 5 and the power
amplification circuit 6 and is converted from an electrical signal to an acoustic signal by the
speaker unit 7 to output a music reproduction sound. At this time, although the microphone 1
receives music reproduction sound, the signal converted to be equal to this is output from the
music compensation circuit 2 and the output of the noise signal processing circuit 3 becomes
zero, which affects the music reproduction. Do not give
[0021]
Next, when external noise enters in the absence of a music signal, the microphone 1 receives the
noise signal and is converted by the noise signal processing circuit 3 into a signal that is in
reverse phase at the muffling point, After passing through the signal addition circuit 5 and the
power amplification circuit 6, the electric signal is converted into an acoustic signal by the
speaker unit 7 and a noise reproduction sound is output. At the muffling point, the extraneous
noise and the noise reproduction sound cancel each other to lower the noise sound pressure
level.
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[0022]
When the music signal and the external noise come in simultaneously, since the abovementioned, the music reproduction sound and the noise reproduction sound are output
independently of each other. Therefore, at the muffling point, the level of the external noise itself
is lowered while the music reproduction sound is the same as when there is no external noise.
[0023]
With the above configuration, the ability to reproduce the music signal is as it is, and when the
external noise comes in, the level is lowered to make it easy to listen to the music reproduction
sound like when there is no external noise. can get. Further, FIG. 3 shows an example in the case
of being mounted on a vehicle, but it can be easily set only by arranging it under a seat or the
like and performing the same connection as a conventional subwoofer. Further, since the
microphone 1 is also attached to the sound reproducing apparatus of the present invention, it is
possible to prevent the occupant's body from touching. Also, when mounted on a vehicle, it is
often used for the purpose of reducing booming noise caused by low frequency cavity resonance
due to road noise, and in this case other noises such as wind noise etc. It becomes unnecessary
noise, and it is desirable that the microphone 1 not receive this. From this point, it is effective to
arrange the microphone 1 under the seat. Further, since the speaker unit 7 as the sound source
and the microphone 1 are in a close distance, for example, even if the characteristics of the
acoustic space change due to opening and closing of the door of the vehicle, etc. Since it is hard
to affect, it also has the effect of making it difficult to cause abnormal phenomena such as
howling.
[0024]
Second Embodiment In the second embodiment of the present invention, a sound absorbing
material is inserted in the recess 8 a of the speaker box 8. In general, the frequency of noise to be
muffled in the sound reproducing apparatus according to the present invention is around 30 to
100 Hz, and usually the sound absorbing material does not absorb sound in the frequency
around this, so noises of other frequencies are suppressed. Thus, signal processing by the electric
circuit can be reduced.
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[0025]
Third Embodiment FIG. 4 shows a sound reproducing apparatus according to a third embodiment
of the present invention. In FIG. 4, the detailed description of the same configuration as that
shown in the first embodiment will be omitted. A printed circuit board 10 has a microphone 1, a
music compensation circuit 2, a noise signal processing circuit 3, a music signal processing
circuit 4, a signal addition circuit 5, and a power amplification circuit 6 mounted thereon. A
connector 9 may be used to connect a power supply for operating the sound reproducing
apparatus of the present invention, a music signal, and the like, which is also mounted on the
printed circuit board 10. The printed circuit board 10 is configured to be fixed to the speaker box
8, and by being fixed, between the separation wall provided on the speaker box 8 and the printed
circuit board 10, an external space serving as a front surface space of the speaker unit Construct
a blocked speaker unit back space. At the same time, the recess 8a is formed inside the outer
periphery of the speaker box 8 and outside the rear space of the speaker unit. In the printed
circuit board 10, it is desirable not to mount a component in a portion in close contact with the
separation wall provided in the speaker box 8, and for assembly, an airtight member or the like is
preferably sandwiched in the close portion. The connector 9 and the microphone 1 are mounted
at prescribed positions on the printed circuit board so as to be disposed in the recess 8 a.
Further, it is desirable that the connector 9 be disposed at a position where it is difficult to touch
from the outside so that the connector as a pair can be inserted and removed.
[0026]
Since these operations are similar to those shown in the first embodiment, the description will be
omitted.
[0027]
According to the above configuration, it is not necessary to form a complicated sealed structure
in the speaker box, and the assembly is facilitated, and hence the cost can be reduced.
[0028]
(Fourth Embodiment) FIG. 5 shows a sound reproducing apparatus according to a fourth
embodiment of the present invention.
In FIG. 5, the detailed description of the same configuration as that shown in the first
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9
embodiment will be omitted.
In FIG. 5, 15 is an auxiliary unit, and the microphone 1 is attached to the inside from the outer
peripheral surface, and a harness for taking out a signal from the microphone 1 is attached. The
connector 9 is electrically connected to the inside of the speaker box 8 through a pair connector
for connecting the main harness. Also, the auxiliary unit 15 is configured to be attached to the
outer peripheral surface of the speaker box 8.
[0029]
Since these operations are similar to those shown in the first embodiment, the description will be
omitted.
[0030]
According to the above configuration, it is possible to share most of the conventional sound
reproducing apparatus intended only for music reproduction and the sound reproducing
apparatus having the noise reduction function in the present invention.
As a result, the mold cost in manufacturing can be reduced, and the effect can be added only
when the noise reduction function is required.
[0031]
Fifth Embodiment FIG. 6 shows a sound reproduction apparatus according to a fifth embodiment
of the present invention. In FIG. 6, the detailed description of the same configuration as that
shown in the first embodiment will be omitted. In FIG. 6, reference numeral 11 denotes a second
microphone, which is fixed inside the speaker unit rear space of the speaker box 8. In the case
where the printed circuit board 10 is used and the printed circuit board 10 is fixed inside the
rear space of the speaker unit, the second microphone 11 may be mounted on the printed circuit
board 10. An acoustic feedback control circuit 12 includes an output of the second microphone
11 as an input and a filter circuit for controlling an output sound pressure characteristic.
Reference numeral 5 denotes a signal addition circuit, which is formed of an addition circuit
which receives the outputs of the noise signal processing circuit 3, the music signal processing
circuit 4 and the acoustic feedback control circuit 12 and electrically adds them.
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[0032]
Next, these operations will be described. The processing of the external noise and the music
signal is the same as that shown in the first embodiment, and the detailed description thereof is
omitted.
[0033]
When the speaker unit 7 is driven, a sound pressure having a phase opposite to that of the
output sound pressure emitted from the speaker box 8 is generated inside the speaker unit rear
space of the speaker box 8. The sound pressure is received by the second microphone 11, and
the output sound pressure is controlled by feeding back the released signal to the original music
signal by the signal addition circuit 5 through the acoustic feedback control circuit 12. it can.
Therefore, the sound reproducing apparatus of the present invention can be tuned to have a
preferable output sound pressure. Further, since the external noise processing and the feedback
signal from the microphone 1 are used, the operation of the acoustic feedback does not affect the
noise signal processing.
[0034]
According to the above configuration, by controlling the output sound pressure characteristic, it
is possible to obtain an effect that a better acoustic characteristic can be realized, and also a
noise reduction can be realized.
[0035]
(Sixth Embodiment) FIG. 7 shows a sound reproducing apparatus according to a sixth
embodiment of the present invention, and in FIG. 7, a detailed description of the same
configuration as that shown in the fifth embodiment is given. Omit.
In FIG. 7, reference numeral 2 denotes a music compensation circuit, which receives the output
of the second microphone 11, and the music reproduction sound output from the sound
reproduction apparatus according to the present invention becomes a signal equal to the signal
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returned to the microphone 1 again. It consists of a filter circuit to make it so. Since the output of
the microphone 11 is a signal similar to the sound pressure characteristic output from the sound
reproducing apparatus according to the present invention, the filter circuit of the music
compensation circuit 2 transmits the acoustic space in which the sound reproducing apparatus
according to the present invention is disposed. It is as easy as simulating a function.
[0036]
Next, these operations will be described. The processing of the music signal and the acoustic
feedback signal is the same as that described in the fifth embodiment, and the detailed
description thereof is omitted.
[0037]
The music compensation circuit 2 to be input to the noise signal processing circuit 3 is a
microphone even if a signal similar to the sound pressure characteristic output from the sound
reproducing apparatus according to the present invention is input from the second microphone
11 1 is converted to be equal to the signal received.
[0038]
The subsequent operation is similar to that shown in the first embodiment.
[0039]
According to the above configuration, since the configuration of the music compensation circuit
2 can be simplified, the cost of parts can be reduced, and the effect of making the operation of
the music compensation more accurate can be obtained.
[0040]
Seventh Embodiment FIG. 8 is a block diagram of a portion related to a failsafe function of a
sound reproduction apparatus according to a seventh embodiment of the present invention.
The other parts are the same as those described in Embodiment 1, and thus the description
thereof is omitted.
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12
In FIG. 8, reference numeral 13 denotes a position recognition means, which moves from a
predetermined position in an acoustic space in which the sound reproducing apparatus of the
present invention is disposed, or the output is active when placed in an acoustically different
environment. It is configured to be
For example, the position recognition means 13 is configured to perform active output with a
desired key, and the desired key is configured to be automatically inserted by placing the sound
reproducing apparatus of the present invention at a predetermined position. Be done. As another
example, a magnet is embedded in a predetermined position, and the position recognition means
13 is configured to remain inactive in response to the magnet, but become active if it deviates
from the predetermined position. Ru. Also, as another example, the position recognition means
13 is in the vicinity of the connector 9, and the pair of connectors 9 is attached to a harness
whose length can reach only the correct position for arranging the sound reproducing apparatus
of the present invention. Also, it has a special structure such as a projection for coupling the
position recognition means 13 to a general purpose connector. There may be a plurality of
position recognition means 13. A fail-safe circuit 14 receives the output of the position
recognition means 13 and also becomes active when the output of the position recognition
means 13 becomes active. When there are a plurality of position recognition means 13, if any of
them becomes active, the output also becomes active. A noise signal processing circuit 3 receives
the output of the failsafe circuit 14 in addition to the output of the microphone 1 and the output
of the music compensation circuit 2, and outputs the noise signal when the output of the failsafe
circuit becomes active. It contains a switch to prevent it.
[0041]
Next, these operations will be described. The processing of the external noise and the music
signal is the same as that shown in the first embodiment, and the detailed description thereof is
omitted.
[0042]
In order to reduce noise, it is necessary to specify an arrangement position in the acoustic space
and set the filter characteristics of the noise signal processing circuit, but if it deviates from the
correct position, the effect of noise reduction is obtained. Becomes smaller, and conversely, noise
increases.
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[0043]
Now, assuming that the sound reproducing apparatus according to the present invention is
moved from a predetermined position, the output of the position recognition means 13 is active,
and the output of the failsafe circuit 14 is also active.
Therefore, the output of the noise signal processing circuit is stopped, and only the music signal
is outputted from the sound reproducing apparatus of the present invention, and the operation of
noise reduction is stopped. As a result, although the noise is not reduced, it is possible to prevent
the noise from being increased due to the erroneous control.
[0044]
With the above configuration, the noise reduction operation is performed so as not to cause
abnormal control when the arrangement position is moved to a place where the muffling effect is
small or can not be obtained because the mounting to a vehicle or the like is easy. The effect of
being able to stop can be obtained.
[0045]
(Embodiment 8) FIG. 9 is a block diagram of a portion related to a failsafe function of the sound
reproduction apparatus according to an eighth embodiment of the present invention.
The other parts are the same as those described in Embodiment 1 or 7, and thus the description
thereof is omitted. In this case, it is assumed to be installed in a car or the like. In FIG. 9,
reference numeral 13 denotes position recognition means, which receives the output of the
microphone 1, the output of the music compensation circuit 2, and the vehicle speed signal of
the car. Here, it is assumed that the vehicle speed signal outputs an active signal only when the
vehicle speed is zero. The position recognition means 13 compares the output of the microphone
1 with the output of the music compensation circuit 2, and when the difference is in the position
of the sound reproducing apparatus of the present invention, the tolerance as the correction
error of the music compensation circuit 2 When it becomes more than the value, it is configured
to be an active output. However, this comparison is performed only when the vehicle speed
signal is active.
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[0046]
Next, these operations will be described. The processing of the external noise and the music
signal is the same as that described in Embodiment 1 or Embodiment 7, and the detailed
description thereof is omitted.
[0047]
First, the case where the sound reproducing apparatus of the present invention is placed at a
predetermined position will be described. When the vehicle speed is 0 and the output from the
microphone 1 is compared with the output from the music compensation circuit 2 in the position
recognition means 13, if there is a music signal, the output from the microphone 1 corresponds
to the feedback of the music signal. Because the difference is only within the correction error in
the music compensation circuit 2. Therefore, the output of the position recognition means 13
becomes inactive. Further, when there is no music signal, there should be no output from the
microphone 1, so the comparison result in the position recognition means 13 is also inactive.
Also, when the music signal is too small, it may be difficult to make a correct comparison in the
position recognition means 13. Therefore, as the condition for performing the comparison, a
certain minimum level of the music signal is set, and more music signals are input. The
comparison operation may be performed only when it is detected.
[0048]
Next, the case where the sound reproducing apparatus of the present invention is moved from a
predetermined position will be described. When the vehicle speed is 0 and the output from the
microphone 1 is compared with the output from the music compensation circuit 2 in the position
recognition means 13, the transfer function of the acoustic space changes, so the output from the
microphone 1 and the music compensation circuit 2 There is a difference between the output
and the output. The change in the transfer function causes an error in the characteristics of the
noise signal processing circuit 3. Therefore, even if the noise reduction operation is performed in
this state, the effect becomes small, and furthermore, the opposite effect is caused and the noise
increases. Conceivable. Therefore, when the difference in comparison in the position recognition
means 13 becomes large, the output can be made active and the noise reduction operation can
be stopped.
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[0049]
With the above configuration, the position recognition function can be operated by itself without
relying on the structure on the vehicle side, and the operation of noise reduction can be stopped
so as not to cause abnormal control when the arrangement position is changed. The effect of
being able to
[0050]
(Embodiment 9) FIG. 10 shows a block diagram of a portion related to a noise signal processing
circuit of a sound reproduction apparatus according to a ninth embodiment of the present
invention.
The other parts are the same as those described in Embodiment 1, and thus the description
thereof is omitted. In FIG. 10, reference numeral 3 denotes a noise signal processing circuit,
which can be constituted by a gain amplifier, various filters and the like, but the case of being
constituted by a gain amplifier and a band pass filter will be described as an example. A filter
characteristic changeover switch 16 is connected to the noise signal processing circuit 3 and is
configured to be able to switch each constant of the noise signal processing circuit 3. The gain
amplifier of the noise signal processing circuit 3 has a plurality of gain switching resistors, and
one of the switches included in the filter characteristic switching switch 16 is connected. Further,
the band pass filter of the noise signal processing circuit 3 has a plurality of cutoff frequency
switching resistors or capacitors, and the other one of the switches included in the filter
characteristic switching switch 16 is connected. The values of the switching resistor and the
switching capacitor described above are set to values at which the muffling performance can be
effectively obtained when the sound reproducing apparatus of the present invention is disposed
in several sound spaces for muffling.
[0051]
Next, these operations will be described. The processing of the external noise and the music
signal is the same as that shown in the first embodiment, and the detailed description thereof is
omitted.
[0052]
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When the sound reproducing apparatus of the present invention is arranged in a known sound
space used when setting each constant of the noise signal processing circuit 3, the filter
characteristic switching is performed so that the constant corresponding to that is obtained. It
suffices to switch the switch 16.
[0053]
Further, when the sound reproducing apparatus of the present invention is disposed in an
unknown sound space which is not used when setting each constant of the noise signal
processing circuit 3, gain switching resistance, cutoff frequency switching If the number of
resistors or capacitors is sufficiently increased, optimum noise reduction characteristics can be
obtained by switching these with the filter characteristics changeover switch 16.
[0054]
According to the above-mentioned configuration, it is possible to realize the silencing of a
plurality of known acoustic spaces by adjusting the changeover switch of one acoustic
reproducing device, and the silencing of an unknown acoustic space is realized by sufficiently
increasing the number of switching. The effect of being able to be realized is obtained.
[0055]
(Embodiment 10) The sound reproducing apparatus according to the tenth embodiment of the
present invention is the same as that shown in the first embodiment except for the portion
relating to the noise signal processing circuit 3, so that the description thereof. Is omitted.
The noise signal processing circuit 3 has a memory for storing information in a digital manner,
and it is possible to set the constant of the constituent elements by the information of the
memory by a gain amplifier, a filter and the like.
More specifically, digital signal processing circuits such as DSPs are often used, and digital filters
such as transversal filters are often used.
Thereby, in the sound reproducing apparatus of the present invention, the constant of the noise
signal processing circuit 3 can be set from the outside.
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[0056]
Next, these operations will be described. For example, by measuring the noise characteristics of a
certain acoustic space such as a vehicle interior, it is possible to obtain the sound pressure level
with respect to the frequency of the noise. At this time, if there is something that indicates a large
sound pressure level at a certain frequency, it is muted. The signal processing pattern in the
noise signal processing circuit 3 can be calculated by comparing the gain shift, the phase shift,
the oscillation margin and the like with the characteristic of the sound reproduction apparatus at
this frequency. This can be defined as a filter constant that minimizes the noise level here when
an error microphone is placed at a point to be muffled, or can be obtained in advance using a
general adaptive system or the like. it can. In the analog signal processing circuit, it can be
represented by constants such as the gain, center frequency, Q constant of the band pass filter,
and the phase shift amount of the phase shifter, and in the digital signal processing circuit, a
transversal filter with n taps Can be represented as n constants A0, A1... A (n-1) in Also, it is
known that the constants of these analog signal processing circuits can be approximately
converted to the constants of digital signal processing circuits.
[0057]
FIG. 11 shows an example of a flow for realizing this. P1 is an external input reading step, and
the determination of the switch state can be used as an example. The gain, center frequency, Q
constant of the band pass filter in analog signal processing, and the phase shift amount of the
phase shifter are set in several stages, and transversal filter constants A0, A1 ... A for all
combinations thereof. (N-1) is stored in advance in the ROM memory. Thereby, in the external
input reading step P1, the type of transversal filter to be used can be determined by reading the
defined switch information. P2 is a filter constant setting step, and a constant corresponding to
the type of transversal filter may be read from the ROM memory. Further, it is conceivable to use
data communication as another example of the external input reading step P1. The configuration
equivalent to the above can be obtained by receiving equivalent information by the data
communication function instead of the switch information, but in this case, the ROM memory is
previously stored in the ROM memory by receiving the transversal filter constant itself. It is also
possible to eliminate the need to set data. P3 is a noise signal input step, which converts an
analog signal received by the microphone 1 into a digital signal. P4 is a digital signal processing
step using a transversal filter or the like, which is converted into a signal set in step P2 and
filtered based on the filter constant. P5 is a noise signal output step, in which the digital signal is
converted back to an analog signal. J1 is a determination step of reset, and it is determined
whether to return to the noise signal input step P3 or return to the external input reading step
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P1. This reset determination step J1 may be eliminated, and a reset due to a system restart by
resetting the power supply may be used.
[0058]
Further, by providing a communication means, a system is configured to automatically adjust so
as to obtain the most effective silencing characteristic simply by arranging the sound
reproducing apparatus of the present invention in an arbitrary sound space. be able to. The
adjustment flow is shown in FIG. P6 is a noise characteristic measurement step of the acoustic
space, and in the state where the noise to be muffled is generated in the acoustic space, the
frequency distribution of the noise is measured. P7 is a selection step of the muffling frequency,
and the muffling frequency which usually indicates the largest level is selected. P8 is a
calculation step of the filter constant, and the filter constant is calculated from the gain shift at
the frequency, the phase shift, the oscillation margin at the peripheral frequency, and the like. P9
is a conversion step to a digital filter, which converts the value obtained in step P8 into a
transversal filter constant. By setting this value in the sound reproduction apparatus of the
present invention by the communication means, the muffling operation can be performed.
[0059]
The above adjustment flow can be configured as an external device of the sound reproduction
apparatus of the present invention, but if the adjustment system is built in the sound
reproduction apparatus of the present invention, the present invention can be applied to any
sound space. It is also possible to automatically adjust the muffling characteristic in a selfcontained manner simply by arranging the sound reproducing device.
[0060]
Further, although the case where only the noise signal processing circuit 3 is realized by the
digital signal processing circuit is described above, the music compensation circuit 2, the music
signal processing circuit 4, the signal addition circuit 5, etc. are also constituted by the digital
signal processing circuit. You may
[0061]
According to the above configuration, muffling of a plurality of acoustic spaces can be realized by
external adjustment, and constant settings can be managed by digital information, so that a
system such as automatic adjustment to any acoustic space can be constructed. An effect is
obtained.
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[0062]
As described above, according to the present invention, it can be mounted on a vehicle etc. very
easily as well as the conventional subwoofer etc. Especially, unpleasant road noises known as
booming noise etc. It can be effectively reduced at the occupant's ear.
[0063]
Also, by arranging under the seat, etc., the microphone is less susceptible to uncontrollable
unnecessary noise, and abnormal control occurs when an occupant touches the microphone or
the window is opened and the wind enters. Can be prevented.
[0064]
Then, when the arrangement position is moved to a place where the muffling effect is small or
can not be obtained because it is easy to mount on a vehicle etc., the muffling operation can be
stopped so as not to cause abnormal control. The advantageous effect is obtained.
[0065]
Brief description of the drawings
[0066]
1 is a cross-sectional view of a speaker used in the sound reproduction apparatus according to
the first embodiment of the present invention.
[0067]
Figure 2 is a block diagram showing the same electric circuit
[0068]
Fig. 3 is a schematic diagram showing an example of mounting on a vehicle
[0069]
4 is a cross-sectional view of a speaker used in the sound reproduction apparatus according to
the third embodiment of the present invention.
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20
[0070]
FIG. 5 is a cross-sectional view of a speaker used in the sound reproduction device according to
the fourth embodiment of the present invention.
[0071]
6 is a block diagram showing a sound reproduction apparatus according to the fifth embodiment
of the present invention.
[0072]
7 is a block diagram showing a sound reproduction apparatus according to the sixth embodiment
of the present invention.
[0073]
FIG. 8 is a block diagram of the main parts showing a sound reproduction apparatus according to
the seventh embodiment of the present invention.
[0074]
FIG. 9 is a block diagram of the main parts showing the sound reproducing apparatus according
to the eighth embodiment of the present invention.
[0075]
<Figure 10> The block diagram of the principal part which shows the sound playback device due
to the 9th form of execution of this invention
[0076]
<Figure 11> Operation explanation figure of the principal part which shows the sound playback
device due to the form of 10th execution of this invention
[0077]
12 is an operation explanatory view of the main part showing the modification
[0078]
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Fig. 13 is a schematic view showing an example of mounting a conventional sound reproducing
apparatus on a vehicle
[0079]
Explanation of sign
[0080]
1 microphone 2 music compensation circuit 3 noise signal processing circuit 4 music signal
processing circuit 5 signal addition circuit 6 power amplification circuit 7 speaker unit 8 speaker
box 9 connector 10 printed board 11 second microphone 12 acoustic feedback control circuit 13
position recognition means 14 Fail-safe circuit 15 Auxiliary unit 16 Filter characteristic
changeover switch
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