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JP2011135279

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DESCRIPTION JP2011135279
The present invention provides a more convenient selection method of measures against
resonance phenomena using the relationship between the characteristics of the ear canal. A
signal processing means for applying a filtering process to an input acoustic signal, a filter
coefficient storage means for holding filter coefficients, and a plurality of filter coefficients stored
in the filter coefficient storage means Filter coefficient determination means for determining
filter coefficients used in the signal processing means; user interface means for presenting
options for filter coefficient determination to the user and obtaining selection results from the
user, the filter coefficient determination means comprising An acoustic signal correction
apparatus characterized in that, when generating the filter coefficient, a filter coefficient used for
the signal processing means is determined by estimating another feature amount from a certain
feature amount of an ear canal acoustic characteristic. [Selected figure] Figure 1
Acoustic signal correction apparatus and acoustic signal correction method
[0001]
The present invention relates to an acoustic signal correction apparatus and an acoustic signal
correction method.
[0002]
It is known that when a human listens in earphones, the ear canal is blocked by the earphones, so
that the listener can hear the listening sounds.
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This is because a resonance phenomenon occurs in the ear canal blocked by the earphones.
[0003]
Relatedly, in Patent Document 1, in the headphone device, a plurality of filter characteristics
having different passing frequency bands are stored in advance for noise cancellation, and any
one of a plurality of filters is selected by operating from the outside. The technology regarding
the setting of the noise cancellation headphone set as a filter characteristic of a digital filter is
described.
[0004]
Further, Patent Document 2 describes a technique for listening to many trial sounds respectively
on the left and right, and selecting an appropriate HRTF.
Further, Patent Document 3 describes a technique regarding hardware for solving the problem of
Patent Document 2.
[0005]
However, in having the function of selecting one from a plurality of settings, a highly convenient
selection method using the relationship between the characteristics of the ear canal has not been
disclosed.
[0006]
JP, 2007-110536, A JP, 5-252, 598 JP, 8, 111, 899, A
[0007]
An object of the present invention is to provide a more convenient selection method of measures
against resonance phenomena using the relationship between the characteristics of the ear canal.
[0008]
In order to solve the above problems, an acoustic signal correction apparatus according to the
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present invention includes a signal processing unit that applies a filtering process to an input
acoustic signal, a filter coefficient storage unit that holds filter coefficients, and the filter
coefficient storage. Filter coefficient determination means for determining a filter coefficient to
be used in the signal processing means from among a plurality of filter coefficients stored in the
means, an option for filter factor determination is presented to a user, and a selection result from
the user is obtained User interface means, wherein the filter coefficient determination means
determines filter coefficients used for the signal processing means by analogying other feature
quantities from certain feature quantities of the ear canal acoustic characteristic when generating
the filter coefficients It is characterized by
[0009]
According to the present invention, it is possible to obtain a more convenient selection method of
measures against the resonance phenomenon using the relationship between the characteristics
of the ear canal.
[0010]
FIG. 1 is a block diagram of an acoustic signal correction apparatus according to an embodiment
of the present invention.
Acoustic characteristic chart of the acquired ear canal.
The resonance frequency distribution figure at the time of earphone wearing in the left ear.
The resonance frequency distribution figure at the time of earphone wearing in the right ear.
The characteristic view which shows distribution of the right-and-left difference of primary
resonance frequency.
The characteristic view which shows distribution of the right-and-left difference of secondary
resonance frequency. The flow chart of processing of the sound signal amendment device of an
embodiment. BRIEF DESCRIPTION OF THE DRAWINGS The external view of the acoustic
apparatus which shows one Embodiment of this invention. The block block diagram of the
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acoustic signal correction apparatus which shows other embodiment of this invention.
[0011]
Hereinafter, embodiments of the present invention will be described. Embodiment 1 Embodiment
1 according to the present invention will be described with reference to FIGS. 1 to 8. First, as a
conventional problem, it is known that when a person listens to an ear with an earphone, the ear
canal is blocked by the earphone, so that the listening sound is heard. This is because a
resonance phenomenon occurs in the ear canal blocked by the earphones. FIG. 2 shows the
acoustic characteristics of the ear canal blocked by the earphones acquired by the microphone
near the open end of the earphone housing in a subject. The horizontal axis represents frequency
and the vertical axis represents gain. In the left and right ears, there is an initial peak (hereinafter
referred to as primary resonance) around 6 kHz. Around 10 kHz, there is a next peak (hereinafter
referred to as second-order resonance). It can be seen that in the left and right ears, the
frequency at which primary resonance occurs (hereinafter, primary resonance frequency) and
the frequency at which secondary resonance occurs (hereinafter, secondary resonance
frequency) are different.
[0012]
FIG. 3 shows the distributions of the primary resonance frequency and the secondary resonance
frequency of the left ear acquired under the same conditions as in FIG. 2 in a plurality of subjects.
FIG. 4 shows the distribution of primary resonance frequency and secondary resonance
frequency of the right ear of the same plurality of subjects. Thus, it can be seen that the
resonance frequency differs depending on the person from about 5.5 kHz to 9 kHz or more, even
if only the primary resonance frequency is described.
[0013]
Patent Document 2 discloses a technique related to an out-of-head localization headphone
listening apparatus as a technique for eliminating a feeling of blockage when headphones are
worn. By clustering different transfer functions for each individual, the types of filter coefficients
necessary for the effect are reduced, and the effort for setting the listener is reduced. However,
the problem is that at least 16 trials are required to determine the appropriate filter coefficients.
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[0014]
For this reason, Patent Document 3 discloses a technique for estimating an appropriate filter
coefficient from measurement data obtained by means of measuring the head shape mounted on
headphones separately from this, and reducing the time and effort for setting the listener. It is
done. However, hardware for measuring the shape is required, and the hardware implementation
cost is increased. There is also the problem that such headphones are not common.
[0015]
The present embodiment relates to a technology that can easily implement an audio device that
eliminates a feeling of stagnation when listening to an earphone. As a technique based on this
embodiment, there is JP-A-2009-194769 (hereinafter referred to as Document 1). In this
document 1, there is disclosed a technique for measuring the resonance frequency in the ear
canal of the listener and performing acoustic correction based on the measurement result to
eliminate the feeling of stagnation of the listening sound. However, this technology requires
hardware for measurement. Therefore, there is a problem that the hardware implementation cost
increases. There is also a problem that it is difficult to obtain such hardware generally.
[0016]
First, the reason why the technology disclosed in Document 1 can be implemented by a simpler
method will be described. According to the measurement results shown in FIG. 3 and FIG. 4, it
can be seen that the primary resonance frequencies are distributed approximately at 5 to 9 kHz.
It can be seen that the secondary resonance frequencies are distributed approximately at 10 to
14 kHz.
[0017]
On the other hand, it is known that the higher the frequency range, the coarser the frequency
resolution. Therefore, in order to generate filter coefficients for suppressing the peaks of the
primary resonance frequency and the secondary resonance frequency, strict matching between
the center frequency of the filter and the resonance frequency is not necessary. For the purpose
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of confirmation, a trial listening experiment was conducted in a pair comparison method with
regard to the influence on audibility in the case of closely matching and in the case of shifting
about 500 Hz before and after. The experiment confirmed that the difference in sound quality
between the two could not be determined. With regard to the secondary resonance frequency
band, acoustic correction is sufficiently possible with a more precise matching. From the above,
in order to reduce the primary resonance phenomenon, for example, it is possible to sufficiently
correct by preparing five types of filters of 5 kHz to 1 kHz. A coarser accuracy match is sufficient
to reduce secondary resonance phenomena.
[0018]
As shown in FIGS. 3 and 4, there is a strong positive correlation between the primary resonance
frequency and the secondary resonance frequency even though the value of the resonance
frequency is largely different depending on the person. For this reason, when the primary
resonance frequency is high, the secondary resonance frequency is also high. By focusing on this
phenomenon, it is understood that the combination of types of filter coefficients for reducing
both the primary resonance and the secondary resonance is reduced. For example, in FIG. 3, in
the case of a person having a 7 kHz primary resonance phenomenon, it can be seen that a
secondary resonance phenomenon occurs at around 12 kHz. There is almost no resonance
phenomenon below 10 kHz or above 13 kHz. Therefore, it is understood that three types of 11 to
13 kHz may be prepared to suppress the secondary resonance phenomenon. In consideration of
the coarseness of the frequency resolution in high band listening, for example, it is sufficient to
prepare a resonance suppression filter aiming to reduce the resonance frequency by 12 kHz.
[0019]
As mentioned above, the types of filters for resonance suppression disclosed in Document 1 can
be limited to several types. By actually listening to a sound to which several types of filters have
been applied, it becomes possible to determine a filter for resonance suppression suited to the
listener. Therefore, no special hardware for measurement is required.
[0020]
FIG. 1 is a block diagram of an acoustic signal correction apparatus according to an embodiment
of the present invention. This acoustic signal correction apparatus is configured by the filter
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coefficient storage unit 104, the signal processing unit 106, the filter coefficient determination
unit 108, the user I / F 110, the output unit 112 and the like.
[0021]
The signal processing means 106 is composed of a digital filter, and applies digital signal
processing to the input acoustic digital signal 102. The output of the signal processing means
106 is input to the output means 112. When the output destination of the output unit 112 is an
earphone or the like having an analog input terminal, digital / analog conversion processing is
performed in the output unit 112, and an analogized electric signal is output to the earphone.
When the output unit 112 is connected to an audio device having a digital input, the digital data
is output as it is to the connected audio device as an electric signal or an optical signal.
[0022]
The filter coefficient storage means 104 stores a plurality of filter coefficients for reducing
higher order resonance phenomena such as primary resonance or primary resonance and
secondary resonance. For example, assuming that the order of the filter is N and the filter
coefficients of primary resonance and secondary resonance are stored, the total number of stored
filter coefficients is, for example, N × 2 = 2N.
[0023]
The filter coefficient storage unit 104 is connected to the filter coefficient determination unit
108. The filter coefficients designated by the filter coefficient determination unit 108 are loaded
from the filter coefficient storage unit 104 into the signal processing unit 106.
[0024]
In the user I / F 110, processing such as providing information to the user for determining the
filter coefficient and acquiring the user intention is performed. FIG. 5 is a characteristic diagram
showing the distribution of the left-right difference of the primary resonance frequency. FIG. 6 is
a characteristic diagram showing the distribution of the left-right difference of the secondary
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resonance frequency. In each case, the horizontal axis represents the difference in frequency and
the vertical axis represents the cumulative number of people.
[0025]
Both primary and secondary resonance frequencies are normal to the left and right. Also, in
consideration of the fact that the difference between the left and the right is within a certain
range, it is possible to analogize that the setting of the right ear should be at a frequency near
that setting if the setting of the left ear is performed. Since this is the same even in the left-right
reverse, after setting of one ear, the time and effort of the remaining one setting is reduced.
[0026]
FIG. 7 shows the flow of processing of the acoustic signal correction device in the present
embodiment. First, in order to check, for example, the primary resonance frequency of the left
ear, the filter coefficient determination unit 108 loads filter coefficients that reduce the primary
resonance of 5 kHz from the filter coefficient storage unit 104 to the signal processing unit 106.
Then, the sound for trial listening is input as an acoustic digital signal 102 to the signal
processing means 106, and the trial sound is output (442). The user listens to the audition sound
and determines whether the correction is suitable for him (444). The determination result is
notified to the filter coefficient determination means 108 via the user I / F 110 (446). If the filter
coefficients do not match, the filter coefficients that reduce the 6 kHz resonance phenomenon
are loaded from the filter coefficient storage unit 104 into the signal processing unit 106 (to 442
for no at 446). The same process is repeated to determine a filter suitable for reducing the
primary ear resonance phenomenon of the left ear (yes at 446). For example, assume that the
result is 7 kHz.
[0027]
After the determination of the primary resonance frequency, in order to examine the secondary
resonance frequency of the left ear, the filter coefficient determination means 108 reduces the
secondary resonance at 12 kHz in addition to the previously determined primary resonance
frequency 7 kHz. Are loaded from the filter coefficient storage means 104 into the signal
processing means 106. This is because, as shown in FIGS. 3 and 4, the listener having a primary
resonance frequency of 7 kHz takes into consideration that the secondary resonance is
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concentrated from 11 kHz to 13 kHz centered on 12 kHz. It is. Then, the sound for trial listening
is input as an acoustic digital signal 102 to the signal processing means 106, and the trial sound
is output (450). The user listens to the trial sound and determines whether the correction is
suitable for him (452). The determination result is notified to the filter coefficient determination
means 108 via the user I / F 110 (454). If the filter coefficients do not match, the filter
coefficients for reducing the 11 kHz resonance phenomenon are loaded from the filter coefficient
storage unit 104 to the signal processing unit 106 instead of 12 kHz (to 450 for no at 454). The
same process is performed, and if the two do not match, the same process is performed at 13
kHz instead of 11 kHz. The same process is repeated to determine the secondary ear resonance
frequency of the left ear (yes at 454). For example, assume that the result is 13 kHz.
[0028]
Next, processing is performed to check the primary resonance frequency of the right ear (460).
The flow of processing is the same as for the left ear, but the starting frequency is changed to 5
kHz to 7 kHz. This is based on the nature that the primary resonance frequency is very close on
the left and right as shown in FIG. If 7kHz does not fit the user's ear, examine nearby 6kHz and
8kHz. As a result, it is possible to reduce the time and effort of listening to the trial sound far
from the primary resonance frequency in the user's ear canal acoustic characteristic.
[0029]
The search for the right ear secondary resonance frequency begins with identifying the first
candidate to present to the user from the left ear secondary resonance frequency result and the
right ear primary resonance frequency result. Referring to the secondary resonance frequency of
the left ear, as shown in FIG. 6, it is based on the nature that the difference between the left and
right of the secondary resonance frequency is small. In this example, we start at 13 kHz. If it does
not fit the user's ear at 13kHz, look at 12kHz or 11kHz. The process flow is similar to that of the
left ear. After selecting the filter coefficients, the user listens to the music (462).
[0030]
As described above, it is possible to narrow down the candidates to be presented to the user by
utilizing the fact that the difference between the right and left resonance frequencies is small and
the positive correlation between the primary resonance frequency and the secondary resonance
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frequency. This makes it possible to enjoy high-quality sound with a small number of times and
without the need for a special hardware device.
[0031]
The mounting location of the acoustic signal correction device of FIG. 1 will be described with
reference to the acoustic device of FIG. When the acoustic signal correction device is built in the
player 90, the acoustic signal filtered using the filter coefficient derived by the filter coefficient
determination means 108 is output to the earphone or headphone 94. Further, the sound signal
correction device may be built in the remote control 92, the earphone or the headphone 94. The
user I / F 110 corresponds to an external operation by the user from the remote controller 92,
for example. The user I / F 110 may be configured to use the user I / F of the player 90.
[0032]
The selection of the frequency may be configured such that the user sounds the sound of each
frequency in turn and presses the determination button of the remote control 92 at that timing.
Alternatively, a display screen for selecting a frequency may be displayed on the player 90 or the
remote controller 92, and the user may move the cursor with the remote controller 92 and press
the enter button.
[0033]
Second Embodiment A second embodiment according to the present invention will be described
with reference to FIGS. 2 to 9. The parts common to the first embodiment will not be described.
Means of determining filter coefficient of filter frequency characteristics for reducing higherorder resonance phenomena such as first-order resonance and second-order resonance as shown
in FIG. 9 instead of holding filter coefficients compared to the first embodiment Determined at
108a. The filter coefficient determination unit 108 a derives filter coefficients according to the
determined frequency characteristics, and outputs the derived filter coefficients to the signal
processing unit 106. The signal processing means 106 performs a filtering process on the
acoustic signal using the set filter coefficient. The output means 112 outputs a signal for
listening to the earphone.
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[0034]
Compared to the first embodiment, the memory for holding the filter coefficient can be reduced.
In addition, filter coefficients can be calculated more accurately as needed. Third Embodiment A
third embodiment according to the present invention will be described with reference to FIGS. 2
to 8 and FIG. 1 or FIG. The parts common to the first and second embodiments will not be
described. A filter that simultaneously corrects both the primary resonance frequency and the
secondary resonance frequency may be generated to allow the user to audition. For example, it is
a filter or the like that corrects 7 kHz as primary resonance and 12 kHz as secondary resonance.
The effect of reducing the number of audition times can be expected.
[0035]
As an effect of the above embodiment, no hardware for measurement is required, a feeling of
stagnation of sound due to occlusion resonance at the time of wearing the earphone is reduced,
and high-quality sound can be enjoyed.
[0036]
It is possible to select an appropriate acoustic correction filter in a manner convenient to the
user.
That is, it is possible to mount an acoustic device that suppresses the feeling of stagnation while
suppressing the number of types of filter coefficients to be prepared for the resonance frequency
at the time of occlusion that differs depending on the person.
[0037]
(Points of Embodiment) (1) A digital signal processing means having a function of hearing with
earphones and performing filter processing for reducing a peak phenomenon of a specific
frequency caused by a resonance phenomenon at the time of occlusion of the ear canal And
means for storing the filter coefficients used in the digital signal processing means, and filter
coefficient determination means for determining the filter coefficients used in the digital signal
processing means among the plurality of filter coefficients stored in the storage means And the
filter coefficient determination means estimates the remaining feature amounts from the selected
one feature amount to determine the filter coefficients used for the digital signal processing
means.
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[0038]
(2) The acoustic apparatus according to (1), wherein the one feature amount is one of the
characteristics of the left and right ears, and the remaining feature amount is the other
characteristic of the left and right ears.
(3) The acoustic apparatus according to any one of (1) and (2), wherein the one feature quantity
is a primary resonance frequency, and the remaining feature quantities are secondary or higher
resonance frequencies. (4) The acoustic measure of (1) to (3), wherein the plurality of filter
coefficients stored in the storage means are filter coefficients determined from characteristics of
a plurality of persons acquired in advance.
[0039]
(5) The sound device of (1) to (4) having not the storage means but the filter generation means.
In the embodiment, as an outline, there is a storage means which has a function of listening with
an earphone, and holds a filter coefficient for performing a filter process for reducing a peak
phenomenon of a specific frequency caused by a resonance phenomenon at the time of occlusion
of the ear canal Filter factor determination means for determining the filter factor to be used for
the digital signal processing means from among the plurality of filter factors stored in the
storage means, the filter factor determination means selecting one of the selected feature
quantities The acoustic device has been described which is characterized by analogizing the
remaining feature amounts from the above and determining the filter coefficients used for the
digital signal processing means.
[0040]
That is, the present invention is characterized in that other feature quantities are estimated from
one selected feature quantity, and filter coefficients are determined. The present invention is not
limited to the above embodiment, and various modifications can be made without departing from
the scope of the invention. In addition, various inventions can be formed by appropriately
combining a plurality of components disclosed in the above-described embodiment. For example,
some components may be deleted from all the components shown in the embodiment.
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Furthermore, the components according to the different embodiments may be combined as
appropriate.
[0041]
104: filter coefficient storage means, 106: signal processing means, 108, 108a: filter coefficient
determination means, 110: user I / F (interface), 112: output means, 90: player, 94: earphone or
headphone, 92: remote control .
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