JP3234784B2 - Transmission voice circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission voice circuit in a telephone.

[0002]

2. Description of the Related Art In a telephone, when a user talks normally, the sound source is separated from a voice source to a receiver, and the sound of the sound is changed depending on the surrounding environment such as a head or surrounding noise. Many. For this reason, conventionally, a transmitting voice circuit is provided in a sound receiving section of a receiver that receives a sound so as to correct the changed characteristics of the transmitting voice.

Conventionally, there has been a transmission voice circuit in a telephone of this type as shown in FIGS.
FIG. 6 is a block diagram showing a configuration of a transmission voice circuit in a conventional telephone, and FIG. 7 is a graph showing sensitivity frequency characteristics in the conventional transmission voice circuit.

First, a configuration of a conventional transmission voice circuit will be described with reference to FIG. 6, reference numeral 101 denotes a microphone provided in the receiver, 102 denotes a microphone amplifier that amplifies an audio signal received by the microphone 101, and 501 denotes a band-pass filter that passes only the audio frequency.

Next, the operation of the conventional transmission voice circuit will be described with reference to FIGS. First, the microphone 10
1 receives the voice uttered by the speaker, and
2 and the microphone amplifier 102 amplifies the speaker voice signal input by the microphone 101 to an appropriate level.
The amplified audio signal passes through a band-pass filter 501 to remove noise outside the audio band.

The sensitivity frequency characteristics include ITU-T
P. Recommendation 35 and G.C. According to Recommendation 121, handset telephones should be of a high-frequency emphasis type in consideration of the correction of the diffraction effect of the head in free space, etc. It is said that it is often flattened.

[0007] Similarly, in a loudspeaker, the IT
UT-TP. According to Recommendation 35, it is desirable to adopt a high-frequency emphasizing type of about 0 to 3 db / octave in consideration of correction of the diffraction effect of the head in free space.

Similarly, in digital telephones, IT
From the U-TP.31 recommendation, taking into account the correction of the diffraction effect of the head in free space, etc., as shown in FIG.
0 to 4 dB / octave at frequencies from z to 1 kHz, 0 to 6 dB at frequencies above 1 kHz
It is desirable to use a high-frequency emphasis type of about / octave.

[0009]

However, in the above-mentioned conventional transmitting voice circuit, the difference in the shape of the telephone or the like is not considered in the frequency characteristics of the band-pass filter. In particular, in mobile phones and PHSs that are becoming smaller and lighter, the size of the microphone, which is a sound receiving point, is away from the mouth due to the size and weight reduction, so that the head of the uttered voice reaches the microphone. The frequency characteristics may change due to diffraction effects or other surrounding influences. Therefore, there is a problem that a voice having a frequency characteristic different from that of the speaker's voice is received by the microphone.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and considers the effects of the diffraction effect of the head at the sound receiving point, and considers the characteristics of the band-pass filter in the transmission voice circuit of the telephone. Is modified so that the frequency characteristics of the voice uttered by the speaker and the frequency characteristics of the voice received by the microphone are the same, and a voice signal having an optimal frequency characteristic is output. An object is to provide an audio circuit.

[0011]

In order to achieve the above object, a transmitting voice circuit according to the present invention firstly divides a voice signal into a plurality of frequency bands, and for each of the divided frequency bands, Band-pass filter (BP
F), and the gain (α) of each band-pass filter is controlled by a sensitivity frequency characteristic adjuster, whereby a transmission voice circuit capable of independently changing a plurality of frequency bands is obtained. Can be

Second, a sensitivity frequency characteristic adjuster controls a band-pass filter previously calculated by a head diffraction analysis method for each divided frequency band (controls the gain of the band-pass filter). To control each band-pass filter according to the value calculated in order to obtain the transmitted voice in consideration of the influence of the head diffraction effect and the like. An audio circuit is obtained.

Third, the sensitivity frequency characteristic adjuster adjusts the transmission voice signal, which has been calculated in advance by the head diffraction analysis method, for each transmission voice level for each divided frequency band. The groups (α11 to αnn) are stored, and the correction gain for each frequency band corresponding to the transmission voice level actually obtained from the transmission voice signal is selected to control the gain of each bandpass filter (BPF). This makes it possible to obtain a transmission voice circuit corresponding to each voice level of the transmission voice and capable of obtaining the transmission voice in consideration of the influence of the head diffraction effect and the like.

Fourth, according to the head diffraction analysis method, the sound uttered by the speaker reaches the microphone which is the sound receiving point.
The amount of change in the sound level changed by the effect of the head diffraction effect is calculated in advance by using the boundary element method, the corresponding correction gain is stored, and the gain of each band-pass filter is controlled by the value. Thus, a transmission voice circuit capable of obtaining a transmission voice that is not affected by the diffraction effect of the head or the like is obtained.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to a band-pass filter that divides an input transmission voice signal into a plurality of frequency bands and passes each of the plurality of frequency band voice input signals. When the sensitivity frequency characteristic adjuster for adjusting the gain of each bandpass filter individually, the divided
Input sound due to the diffraction effect of the head for each frequency band
A head diffraction analysis unit that calculates the amount of change in voice level,
The sensitivity frequency characteristic adjuster is located in the head diffraction analysis unit.
Of audio level for each divided frequency band calculated by
Stores the correction gain of each bandpass filter corresponding to the amount
A storage device, and each divided frequency band extracted from the storage device
The use of each band-pass filter using the correction gain for each band
And a filter control device for controlling the gain.
And taking into account the effects of diffraction effects on the head, etc.
Controlled to be a bandpass filter with sensitivity frequency characteristics
It has the effect that it can be controlled.

According to a second aspect of the present invention, the head
Diffraction analysis part has diffraction effect of head for each divided frequency band
Audio signal received the change in input audio level due to the influence of
Calculated according to the level of the signal, the sensitivity frequency characteristic adjuster
Indicates the audio level of the received audio signal for each divided frequency band.
A voice level detection circuit for detecting the
Of each band-pass filter corresponding to the amount of change in
A storage for storing a correction gain, and the audio level detection circuit
Level of the audio signal received for each divided frequency band from
From the storage device according to the
Filter characteristic selector for selecting the gain, and the filter characteristic
Each bandpass filter according to the correction gain selected by the selector
Filter control device for controlling the gain of the filter.
The audio level changes from moment to moment.
Responding and taking into account the effects of diffraction effects on the head, etc.
Controlled to be a bandpass filter with sensitivity frequency characteristics
It has the effect that it can be controlled.

According to a third aspect of the present invention, the head
Part diffraction analysis part, the shape of the head and phone to be analyzed,
Receiving at least one analysis condition of the physical property data,
And the phone are divided into boundary elements,
Analysis data setting to set the sound source at the position of the mouth of the head
And a sound radiated from the sound source reaches a predetermined sound receiving point.
An acoustic characteristic calculation unit for determining a frequency characteristic of the reached sound,
Frequency characteristics of the sound source and frequency characteristics at the sound receiving point
To calculate the difference, and calculate the
Change stored in the memory as a correction gain to control the gain
It is equipped with an amount calculation unit and has different shapes
On the phone, diffraction of the head on each phone
Calculate the effects of the bandpass filter
Has the effect that the data can be controlled.

[0018]

(Embodiment 1) Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings and FIGS. FIG. 1 is a block diagram showing a configuration of a transmission voice circuit according to a first embodiment of the present invention. FIG. 2 is a block diagram showing a configuration of a transmission voice circuit according to a second embodiment of the present invention. FIG. 4 is a block diagram showing in detail a configuration of a sensitivity frequency characteristic adjuster of a transmission voice circuit according to a third embodiment of the present invention, and FIG. 4 is a block diagram illustrating a transmission voice circuit according to a fourth embodiment of the present invention. FIG. 5 is a block diagram showing a configuration of a head diffraction analysis unit to be used. FIG. 5 is a diagram showing a sound source and a sound arrival at a sound receiving point for explaining the head diffraction analysis unit according to the fourth embodiment of the present invention shown in FIG. FIGS. 7A and 7B are graphs showing examples of the frequency response of the sound source, wherein FIG. 7A shows the frequency response (sound level) of the sound source, and FIG. FIG.

First, with reference to FIG. 1, the configuration of the transmission voice circuit according to the first embodiment of the present invention will be described. FIG.
, 101 is a microphone equipped on the handset, 1
Reference numeral 02 denotes a microphone amplifier for amplifying a transmission voice signal received by the microphone 101, and reference numerals 105 to 107 denote a voice frequency band divided into a plurality of (n) frequency bands by n. A bandpass filter (BPF) connected in parallel so as to pass a voice signal.

Reference numeral 104 denotes a band-pass filter (BPF) group including band-pass filters (BPFs) 105 to 107 of each frequency band, and reference numeral 103 denotes each band-pass filter 105.
To 107 are sensitivity frequency characteristic adjusters that supply values for adjusting respective frequency characteristics (for example, correction gains α1, α2,..., Αn for correcting the gain of each band-pass filter). Bandpass filters 105 to 10
7 is an adder that adds the outputs of the 7 and outputs a transmission voice signal whose frequency characteristics have been corrected.

Next, the operation of the transmission voice circuit according to the first embodiment of the present invention will be described with reference to FIG. First, the speaker voice signal input to the microphone 101 is amplified to an appropriate level via the microphone amplifier 102 and input to the transmission voice circuit. Next, a correction gain (for example, α1, α2,..., Αn) corresponding to each of the band-pass filters 105 to 107 of the band-pass filter (BPF) group 104 is preset from the sensitivity frequency characteristic adjuster. An example of the setting will be described later).
To 107, whereby the band-pass filters 105 to 107 are controlled.

It is not necessary to divide the audio frequency band into n equal parts. For example, the audio frequency band may be divided for each critical bandwidth. The signal that has passed through the band-pass filter group 104 is input to the adder 108, synthesized again as one transmission voice signal, and output to the next stage.

The transmission voice circuit in the present embodiment is configured as described above, so that the frequency characteristics of the transmission voice signal for each divided frequency band can be independently transmitted through the plurality of band-pass filters 105 to 107. By performing the correction or the change, it is possible to adjust the transmitted voice signal so as to have a preferable frequency characteristic as a whole.

(Embodiment 2) Next, referring to FIG.
The configuration of the transmission voice circuit according to the second embodiment of the present invention will be described. FIG. 2 is a diagram showing the sensitivity frequency characteristic adjuster 103 in FIG. 1 in detail. In FIG.
Reference numerals 105 to 107 denote a band pass filter (BPF) connected in parallel so as to pass a transmission voice signal of each frequency band for each divided frequency band by dividing the voice frequency band into a plurality of (n) frequency bands. , 104 are a group of band-pass filters (BPF) consisting of band-pass filters (BPF) 105 to 107 of each frequency band.

Reference numeral 103 designates a filter control device 201 and a storage device 202.
107 is a value for adjusting each frequency characteristic (for example, a correction gain α for correcting each band-pass filter).
1, α2,..., Αn), the sensitivity frequency characteristic adjuster 203 determines the frequency response (voice level) of the sound source for each frequency band and the frequency response (voice level) of the arrival sound at the sound receiving point. This is a head diffraction analysis unit that calculates correction gains (α1 to αn) (to be described in detail later). Also,
The storage unit 202 stores the calculated correction gains (α1 to αn), and the filter control device 201 stores the correction gains (α1 to αn).
n) correspond to the corresponding bandpass filters 105 to 10 respectively.
7 to control the gain for the transmitted voice signal.

Next, the operation of the transmission voice circuit according to the second embodiment of the present invention will be described with reference to FIG. First, at the time of a test, at the time of manufacture, at the time of shipment, or the like, the head diffraction analysis unit 203 previously calculates correction gains (α1 to αn) for each frequency band, and
02 is stored. (An example of a method of calculating the correction gain (α1 to αn) by the head diffraction analysis unit 203 will be described later.) At this time, the storage unit 202 stores the correction gain (α1) for each divided frequency band as shown in [Table 1]. ~ Αn) data is stored. The filter control device 201 uses the values (correction gains α1 to αn) stored in the storage unit 202 to control the respective bandpass filters 105 to 107 for the audio signals of the respective frequency bands input to the respective bandpass filters 105 to 107. Control the gain.

The transmission voice circuit according to the present embodiment is configured as described above, and has a band having a preferable sensitivity frequency characteristic in which the sensitivity frequency characteristic of the voice signal affected by the diffraction effect of the head is corrected. Pass filter 105
~ 107 can be adjusted.

[0029]

(Embodiment 3) Next, referring to FIG.
The configuration of the transmission voice circuit according to the third embodiment of the present invention will be described. FIG. 3 shows the sensitivity frequency characteristic adjuster 1 shown in FIG.
It is a figure which shows the part of 03 in more detail. In FIG.
Since the microphone 101, the microphone amplifier 102, the band-pass filter group 104, and the band-pass filters 105 to 107 have been described in detail in FIG. 1, further detailed description will be omitted.

Reference numeral 103 shown in FIG.
01, a filter characteristic selector 302, and a storage device 202
And a sensitivity frequency characteristic adjuster 203 constituted by the filter control device 201, based on the frequency response (voice level) of the sound source for each frequency band and the frequency response (voice level) of the arrival sound at the sound receiving point, [ As shown in Table 2],
The correction gain (α11) at each audio level of the input audio signal
To αnn).

The voice level detection circuit 301 detects the voice level of the transmission voice signal input for each frequency band, and the storage unit 202 stores the correction gains (α11 to αnn) calculated by the head diffraction analysis unit 203. The filter characteristics selector 302 stores the correction gains (α11 to αn) corresponding to the voice level of the transmission voice signal detected by the voice level detection circuit 301.
n) is selected from the storage device 202, and the filter control device 20 is selected.
Numeral 1 designates the selected correction gains (α11 to αnn) as band-pass filters 105 to 107 of the corresponding frequency bands.
To control the gain for the transmitted voice signal passing therethrough.

Next, the operation of the transmitting voice circuit according to the third embodiment of the present invention will be described with reference to FIG. First, the speaker voice signal input to the microphone 101 is
Bandpass filter group 104 through microphone amplifier 102
And input to the audio level detection circuit 301, where the audio level of each frequency band is detected at regular intervals.

The filter characteristic selector 302 stores the
From the values of the correction gains (α11 to αnn) stored in Table 2 (Table 2), filter characteristics for each frequency band corresponding to the detected audio level, that is, correction gains (α
11 to αnn). Filter characteristic selector 3
02 (α11-αnn)
Are passed to the filter control device 201 and the correction gains (P1 to P1)
Each of the band-pass filters 105 to 107 is controlled as Pn).

When the voice level input to the voice level detection circuit 301 is low and there is no voice signal of the speaker, muffling data (for example, muffling data) for eliminating ambient noise is used.
ANC, etc.) is stored in the storage device 202, and when such a small sound level is detected, the ambient noise can be reduced by using the muffling data.

[0036]

With the above configuration, the transmission voice circuit according to the present embodiment is adapted to follow the voice level of the speaker's transmission voice signal, which changes from moment to moment, in each frequency band. A band-pass filter 1 having a preferable sensitivity frequency characteristic in which the sensitivity frequency characteristic of an audio signal affected by a diffraction effect of the head is corrected for each level.
It can be adjusted so as to have a value of 05 to 107.

(Embodiment 4) Next, referring to FIG.
The configuration of the transmission voice circuit according to the fourth embodiment of the present invention will be described. FIG. 4 is a diagram showing the head diffraction analyzer 203 shown in FIGS. 2 and 3 in detail.

The head diffraction analysis unit 203 includes a head / telephone information input unit 402 for inputting model information (analysis conditions) such as the shape of the head / telephone to be analyzed and physical property data, and a sound source such as a human utterance. Sound source information such as sound pressure or frequency of the sound source (a sound source having a known frequency characteristic can be set at the position of the mouth of the modeled head).
03, a sound receiving point information input unit 404 for inputting sound receiving point position information, and an element dividing unit 405 (details will be described later) for dividing a head, a telephone, and the like into respective boundary elements. A setting unit 401, an acoustic characteristic calculating unit 406 that calculates acoustic characteristics (frequency characteristics) of a sound arriving at a predetermined sound receiving point when the sound emitted from the sound source reaches a predetermined sound receiving point, And a change amount calculation unit 407 that calculates a change amount of the sound level at the sound receiving point from a difference from the frequency characteristic of the sound source.

Next, with reference to FIGS. 4 and 5, the operation of the head diffraction analyzing section 203 of the transmission voice circuit according to the fourth embodiment of the present invention (the correction gain is determined by the head diffraction analyzing method). The operation of calculating and setting) will be described in detail. First, model information such as shape and physical property data (for example, reflectance) of the head / telephone is input from the head / telephone information input unit 402. The shape of the head is, for example, ITU-T
P. 58 Use the dummy head shape and the like specified in the Recommendation.

Next, the element dividing section 405 divides the head, the telephone, and the like into respective boundary elements and outputs the boundary elements. When dividing the head and the telephone, etc. into boundary elements, there is some difference before and after depending on the solver (calculation engine), but the length of one side of the divided surface is determined by the analysis upper limit frequency (for voice, for example, 340
It is said that it is necessary to make the length about 1/6 of the wavelength (about 0 Hz). That is, if it is longer, the calculation accuracy is reduced, and if it is shorter, the calculation takes a long time. In the case of a telephone, it is only necessary to be able to analyze up to about 3400 Hz. For example, in order to analyze up to 3400 Hz, the length of one side of the division surface is divided into smaller than 1.6 cm which is あ る of the wavelength. Need to be.

Further, sound source information such as sound pressure and frequency of a sound source (human utterance) is input from a sound source information input unit 403. For example, the sound source information may be a point sound source having a flat frequency characteristic or a sound source having the same characteristics as a human voice. Also, the position information of the sound receiving point, that is, the distance from the sound source to the sound receiving point is input from the sound receiving point information input unit 404.
Further, although not shown in FIG. 4, audio level information of each input audio signal to be considered (for example, audio levels A1 to An in Table 2) can be added.

After the input of the above information is completed, the acoustic characteristics (frequency characteristics) at the sound receiving point from the sound source by the boundary element method.
Is calculated by the acoustic characteristic calculation unit 406. Change amount calculator 40
7 compares the frequency characteristic at the sound receiving point obtained from the calculation result with the frequency characteristic of the sound source, and, based on the comparison, calculates the amount of change in the audio level corresponding to the level of the audio signal input for each frequency band. Ask. For each frequency band,
The amount of change in each audio level obtained in accordance with the input audio level is represented by a corresponding correction gain (α11 to αnn).
Is stored in the storage device 202. Then, the correction gains (α11 to αnn) are used for gain control of the band-pass filters 105 to 107 in the first to third embodiments.

With the transmission voice circuit according to the present embodiment configured as described above, in each frequency band, the sensitivity frequency of the voice signal affected by the diffraction effect of the head, etc., is determined for each voice level. Analysis data for correcting the characteristic is calculated in advance, and the correction gain (α11 to αn) is thereby calculated.
By setting and storing n), the sensitivity frequency characteristic of the audio signal affected by the diffraction effect of the head or the like can be adjusted according to the audio level of the transmitted audio signal of the speaker that changes every moment. It can be adjusted to have bandpass filters 105-107 having modified preferred sensitivity frequency characteristics.

FIG. 5 is a frequency response diagram showing an example of the frequency response of the sound source and the frequency response of the arrival sound at the sound receiving point.
(A) shows the frequency response (voice level) of the sound source,
(B) is a graph showing a comparison between the frequency response of the sound source and the frequency response of the arrival sound at the sound receiving point. The frequency characteristics of the sound source and the frequency characteristics at the sound receiving point are compared for each frequency band (f1, f2,..., Fn), and the level difference (α
1, α2,..., Αn) are stored in the storage unit 202. The level difference (α1, α2,..., Αn) with respect to the input sound signal at the sound receiving point is eliminated through a band-pass filter, so that the effect due to the diffraction effect of the head and the transmission due to the difference in the sound receiving point, etc. Deterioration of speech sound quality can be prevented.

[0046]

The transmission voice circuit according to the present invention is constructed as described above. In particular, the voice signal is divided into a plurality of frequency bands, and each divided frequency band passes the frequency of the frequency band. A bandpass filter was provided, and the gain of each bandpass filter was controlled independently by the sensitivity frequency characteristic adjuster, corresponding to the level of the input audio signal, and was affected by the diffraction effect of the head, etc. A transmission voice circuit having a band-pass filter that can correct the sensitivity frequency characteristic of the audio signal to a desirable sensitivity frequency characteristic is obtained.

The transmission voice circuit according to the present invention is configured as described above. In particular, the gain of each band-pass filter is adjusted according to the level of the input transmission voice signal by the head diffraction analysis method using the boundary element method. By controlling the band-pass filter by calculating from the amount of change calculated by
A transmission voice circuit capable of faithfully reproducing the voice of the speaker at the microphone position is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a transmission voice circuit according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a transmission voice circuit according to a second embodiment of the present invention;

FIG. 3 is a block diagram showing in detail a configuration of mainly a sensitivity frequency characteristic adjuster of a transmission voice circuit according to a third embodiment of the present invention;

FIG. 4 is a block diagram showing a configuration of a head diffraction analyzer used in a transmission voice circuit according to a fourth embodiment of the present invention.

FIG. 5 is a graph showing an example of a frequency response between a sound source and a sound arrived at a sound receiving point for explaining the head diffraction analyzing unit according to the fourth embodiment of the present invention shown in FIG. 4;
(A) is a diagram showing a frequency response (voice level) of a sound source. (B) is a diagram showing a comparison between a frequency response of a sound source and a frequency response of a sound source at a sound receiving point.

FIG. 6 is a block diagram showing a configuration of a transmission voice circuit in a conventional telephone.

FIG. 7 is a graph showing sensitivity frequency characteristics in a conventional transmission voice circuit;

[Explanation of symbols]

 Reference Signs List 101 microphone 102 microphone amplifier 103 sensitivity frequency characteristic adjuster 104 band-pass filter group 105 to 107 band-pass filter 108 adder 201 filter control device 202 storage device 203 head diffraction analysis unit 301 audio level detection circuit 302 filter characteristic selector 401 analysis Data setting unit 402 Head / phone information input unit 403 Sound source information input unit 404 Sound receiving point information input unit 405 Element division unit 406 Acoustic characteristic calculation unit 407 Change amount calculation unit 501 Band-pass filter

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04M 1/00 H04M 1/24-1/253 H04M 1/58-1/62 H04M 1/66-1/82 H04B 7 / 24-7/26 102 H04Q 7/00-7/38 H04B 3/20-3/23

Claims (3)

(57) [Claims] An input transmission voice signal is divided into a plurality of frequency bands, and a band-pass filter for passing the voice input signal in each of the plurality of frequency bands, and a sensitivity for individually adjusting a gain of each band-pass filter. A frequency characteristic adjuster ;
Due to the effect of head diffraction effect for each divided frequency band
A head diffraction analyzer that calculates the amount of change in the input sound level
The sensitivity frequency characteristic adjuster is provided with the head diffraction analyzer
Audio level for each divided frequency band calculated in
The correction gain of each band-pass filter corresponding to the
Memory to be stored and each of the divided sections taken out from the memory.
Each of the bandpass filters is corrected using a correction gain for each wavenumber band.
A transmission voice circuit, comprising : a filter control device for controlling a gain of the transmitter. 2. The head diffraction analysis unit according to claim 1, wherein
Of the input sound level due to the diffraction effect of the head and the head
The amount is calculated according to the level of the received audio signal, and
Frequency frequency adjuster adjusts the audio level of the received audio signal.
Audio level detection circuit that detects each divided frequency band
And the amount of change in the calculated input voice level.
A memory for storing the correction gain of each bandpass filter;
Received from the audio level detection circuit for each divided frequency band.
Each band is stored from the storage device according to the level of the sound signal.
Filter characteristic selector for selecting the correction gain of the pass filter
And a correction gain selected by the filter characteristic selector.
Filter system that controls the gain of each band-pass filter according to
The transmission voice circuit according to claim 1, further comprising a control device . 3. The head diffraction analysis section includes a head to be analyzed and a head diffraction analysis section.
Analysis of at least one of the shape and physical properties data of the phone and the phone
Receive conditions and split head and phone into boundary elements
Sound source at the mouth of the modeled head.
An analysis data setting unit to determine the sound radiated from the sound source
Finds the frequency characteristics of the sound that reaches the predetermined sound receiving point
An acoustic characteristic calculator, frequency characteristics of the sound source and the sound receiving point
And calculate the difference by comparing the
The above correction gain for controlling the gain of the bandpass filter is described above.
It is characterized by having a change amount calculation unit for storing in memory
The transmission voice circuit according to claim 1 or 2 .