KR102306739B1 - Method and apparatus for voice enhacement in a vehicle - Google Patents

Abstract

The present invention relates to a method and device for enhancing voice transmission in a vehicle. More specifically, the present invention relates to the method and device that amplify and transmit a voice of a specific passenger in the vehicle to a location of another passenger. According to the present invention, provided is the method and device for enhancing the voice transmission in the vehicle that allow the hearing passenger to hear a sufficient level of voice by allowing the voice of the specific passenger in the vehicle to be amplified and transmitted to the location of another passenger, and allow a conversation to be proceeded while concentrating on driving. The device for enhancing the voice transmission in the vehicle comprises: a resonance removing part; and a voice suppression part.

Description

Method and apparatus for voice enhancement in a vehicle

The present invention relates to a method and apparatus for enhancing voice transmission inside a vehicle, and more particularly, to a method and apparatus for amplifying and transmitting the voice of a specific occupant in a vehicle to another occupant's location.

In the vehicle, due to noise while driving, voice transmission between passengers may be reduced. When the voice transmission power is deteriorated in this way, in order to ensure that the listening occupant can hear the other occupant's words, it may cause situations such as focusing on the voice of the other occupant at an insufficient level or turning their gaze to the other occupant, leading to a car accident. There was a problem that had a risk of being connected.

US 10-1178313 B1

The present invention was devised to solve such a problem, and the voice of a specific occupant in the vehicle is amplified and transmitted to the position of another occupant, so that the listening occupant hears a voice of a sufficient level, so that the conversation proceeds while concentrating on driving. It is an object of the present invention to provide a method and apparatus for enhancing voice transmission within a vehicle.

In order to achieve the above object, the device for enhancing voice transmission in a vehicle according to the present invention is a signal of a sum signal of voice input to a corresponding microphone, noise, and an echo from the speaker to the corresponding microphone for each microphone provided in the vehicle. an echo canceling unit for receiving and removing the echo therefrom; and a noise suppressor for performing noise suppression on the signal from which the echo is removed for each of the microphones, wherein when M microphones and K speakers are provided in the vehicle, the echo canceling unit may include the M microphones Correspondingly, provided with M x K acoustic echo canceller (AEC) modules for canceling K echoes introduced in the path from each of the K speakers to the corresponding microphone, the noise suppression unit comprising: Corresponding to each of the M microphones, M noise suppressor modules that perform noise suppression on a signal from which echo is removed are provided, wherein the in-vehicle voice transmission enhancement device uses a gain matrix Thus, it further includes a gain matrix application unit for matching the M microphone signals to which the noise suppression is performed by the noise suppression unit and a speaker to which each signal is to be output.

Each of the echo cancellation modules may include: an echo cancellation adaptive filter for generating an echo cancellation signal for canceling the echo from a signal in which voice, noise, and echo are combined; and an LMS algorithm performing unit that updates the echo cancellation adaptive filter through the LMS algorithm using the echo cancelled sum signal of voice and noise and the speaker output signal.

The gain matrix application unit may further include a function of setting an audio output gain for output to a speaker with respect to the microphone signal on which the noise suppression has been performed.

The in-vehicle voice transmission enhancement device may include: a noise level analyzer for estimating an environmental noise level from a noise spectrum in the noise suppressor; and a level setting unit configured to determine an audio output gain to be output to a speaker from the estimated environmental noise level.

The level setting unit may determine the gain level by increasing the gain of the gain matrix as the estimated environmental noise increases and decreasing the gain of the gain matrix as the noise decreases.

When the environmental noise level is smaller than a specific value (hereinafter referred to as a 'first reference level'), the gain is maintained at a preset specific value (hereinafter referred to as a 'first gain level'), and the environmental noise level is a different specific value (hereinafter referred to as a 'first gain level') Hereinafter, when it is greater than the 'second reference level'), the gain may be maintained at another predetermined specific value (hereinafter referred to as a 'second gain level').

According to another aspect of the present invention, in the method for enhancing voice transmission inside a vehicle, (a) for each microphone provided in the vehicle, the sum signal of the voice input to the microphone, the noise, and the echo from the speaker to the microphone receiving and canceling the echo therefrom; and, (b) for each of the microphones, performing noise suppression on the signal from which the echo is removed. After the step (b), (c) using a gain matrix, the noise The method further includes matching each microphone signal to which suppression has been performed and a speaker to which each signal is to be output.

When canceling the echo, for each microphone received signal, each echo introduced in the path from each speaker to the corresponding microphone is removed, and the noise suppression is performed on the signal from which each echo is removed. can

Prior to performing the matching in step (c), the method may further include (c0) setting an audio output gain for output to a speaker with respect to the microphone signal on which the noise suppression has been performed.

The step (c0) may include (c01) estimating an environmental noise level from a noise spectrum measured during noise suppression; and, (c02) determining an audio output gain to be output to a speaker from the estimated environmental noise level.

The gain level of the audio output gain may be determined by increasing the gain of the gain matrix as the estimated environmental noise increases and decreasing the gain of the gain matrix as the noise decreases.

When the environmental noise level is smaller than a specific value (hereinafter referred to as a 'first reference level'), the gain is maintained at a preset specific value (hereinafter referred to as a 'first gain level'), and the environmental noise level is a different specific value (hereinafter referred to as a 'first gain level') Hereinafter, when it is greater than the 'second reference level'), the gain may be maintained at another predetermined specific value (hereinafter referred to as a 'second gain level').

According to the present invention, the voice of a specific occupant in the vehicle is amplified and transmitted to another occupant's location, so that the listening occupant hears a voice of a sufficient level, so that a conversation can proceed while concentrating on driving. And there is an effect of providing a device.

1 is a schematic diagram illustrating voice transmission in a conventional vehicle and voice transmission in a vehicle in which an apparatus for enhancing voice transmission according to the present invention is installed.
2 is a block diagram showing a case in which one microphone and one speaker are installed in the apparatus for enhancing voice transmission according to the present invention;
3 is a diagram illustrating a block diagram in the case where two microphones and two speakers are installed in the apparatus for enhancing voice transmission according to the present invention;
4 is a block diagram showing a case in which M microphones and K speakers are generally installed in the apparatus for enhancing voice transmission according to the present invention.
FIG. 5 is a view for explaining the relationship between a microphone and a speaker in a vehicle when M=4 and K=6 in FIG. 4;
FIG. 6 is a block diagram illustrating a case in which a gain adjustment unit according to environmental noise level analysis is further provided in the apparatus for enhancing voice transmission of FIG. 4; FIG.
7 is a diagram illustrating a gain determination curve according to an environmental noise level;
8 is a flowchart of a method for enhancing speech delivery performed by the apparatus for enhancing speech delivery according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms or words used in the present specification and claims should not be construed as being limited to conventional or dictionary meanings, and the inventor should properly understand the concept of the term in order to best describe his invention. Based on the principle that it can be defined, it should be interpreted as meaning and concept consistent with the technical idea of the present invention. Therefore, the configuration shown in the embodiments and drawings described in the present specification is only the most preferred embodiment of the present invention and does not represent all of the technical spirit of the present invention, so at the time of the present application, various It should be understood that there may be equivalents and variations.

1 is a schematic diagram illustrating voice transmission in a conventional vehicle and voice transmission in a vehicle in which an apparatus for enhancing voice transmission according to the present invention is installed.

1A is a diagram illustrating a voice transmission process in a conventional vehicle. As shown in the figure, the driver's voice facing forward is transmitted relatively indistinctly to the passengers in the rear seat. In addition, although not shown, the voice of the rear seat passenger is not clearly audible to the front passenger or the driver due to the influence of the front seat seat and the like and the reflection sound of the vehicle body.

On the other hand, in the vehicle in which the voice transmission enhancing device of the present invention of FIG. 1(b) is installed, as shown in the figure, the driver's voice received from the microphone 1 is controlled by the speaker ( 2,3) directly to the rear-seat passengers, the rear-seat passengers can hear the driver's voice more clearly, and the same applies to the process in which the rear-seat passengers' voices are transmitted to the front-seat passengers or the driver. Of course, in this process, noise cancellation, echo cancellation, and amplification output are performed by the voice transmission enhancing device, which will be described in detail below with reference to FIGS. 2 to 7 .

2 is a block diagram illustrating a case in which one microphone and one speaker are installed in the apparatus 200 for enhancing voice transmission according to the present invention.

In this system, noise and voice from the microphone 110 and echo generated from the speaker 120 are introduced. The block diagram of FIG. 2 is a structure in which a sound is output to the speaker 120 by removing noise while removing an echo from the signal collected by the microphone 110 .

This single microphone and single speaker input/output structure is very similar to that of the existing hands-free or conference phone, but in this case, your own voice (Tx in a call) is heard from the other party (Rx in a call) without the voice of the other party It is characterized by being During a call, the case where you and the other party talk together is called double talk. ), there is always a double talk situation. Therefore, this system requires high-performance echo cancellation and noise reduction technology and tuning so that there is no sound interruption in a double talk situation.

Referring to FIG. 2 , P(z) 10 denotes a path through which an echo is transmitted from a speaker 120 to a microphone 110 in a vehicle. In the microphone 110, the voice (v(n)), the noise (n(n)), and the echo signal (f(n)) passed through the P(z)(10) are summed (20) m( n) is introduced into the echo canceller 210 as a signal. The echo cancellation signal f' ( n), and this echo cancellation signal f'(n) is summed with the microphone signal m(n) (=v(n)+n(n)+f(n)) introduced from the microphone (213), After the echo signal f(n) is canceled by the echo cancellation signal f'(n), a v(n)+n(n) signal is generated. The v(n)+n(n) signal passes through the noise suppression unit 220 to suppress noise, and the signal y(n) output from the noise suppression unit 220 is output from the speaker 120 . In addition, y(n) and the aforementioned v(n)+n(n) are input to the LMS algorithm performing unit 211 of the AEC of the echo canceling unit 210 , and the LMS algorithm performing unit 211 may cancel the echo therefrom. The adaptive filter A(z) 212 is continuously updated.

3 is a block diagram illustrating a case in which two microphones and two speakers are installed in the apparatus 200 for enhancing voice transmission according to the present invention.

Since there are a total of four echo paths (P ₁₁ , P ₂₁ , P ₁₂ , P _{22 ), there are four AECs (AEC 11} , AEC ₂₁ , AEC), which are the echo cancellation modules of the echo canceller 210 . ₁₂ , AEC ₂₂ ), the speaker output unit becomes two ( 121 , 122 ), and there are two NS (noise suppressor), which is a noise suppressor module of the noise suppressor 220 for the final two signals synthesized after echo cancellation (NS ₁₎ , NS ₂ ). At this time, two NS means that there is one NS for each microphone, and therefore _{, subscripts in NS 1} and NS ₂ mean each microphone number.

In P ₁₁ , P ₂₁ , P ₁₂ , and P ₂₂ , the preceding subscript is the speaker number, and the latter is the microphone number. In _{the case of P 21} , it means an echo path coming out of the speaker No. 2 122 and entering the microphone No. 1 111 . Also, in each module AEC ₁₁ , AEC ₂₁ , AEC ₁₂ , and AEC ₂₂ of the echo canceller 210 , the preceding subscript means a speaker number, and the rear subscript means a microphone number. In _{the case of AEC 21} , it is an echo canceling module for the echo coming out of the speaker No. 2 (122) and entering the microphone No. 1 (111).

That is, the signal m _{1 (n) input from the left microphone 111 passes through AEC 11} , AEC ₂₁ which is an echo cancellation module corresponding to _{P 11} , P ₂₁ , which is a path through which an echo enters the left microphone 111 , P ₁₁ and P ₂₁ respectively, the echo is removed, and then the noise is removed through _{NS 1 before output to the right speaker 122 .} In FIG. 2, the sum 213 of m(n) and the echo cancellation signal f'(n), shown inside the echo cancellation (AEC) module, is shown outside of each AEC module in FIG. 3 for convenience (213) However, the same part is shown.

Conversely, the signal m _{2 (n) input from the right microphone 112 goes through AEC 12} , AEC ₂₂ , which is an echo cancellation module corresponding to _{P 12} , P ₂₂ , which is the path where the echo enters the right microphone 112 . As a result _{, the echo from each of P 12} and P ₂₂ is removed, and then the noise is removed through _{NS 2} before output to the left speaker 121 .

4 is a block diagram illustrating a case in which M microphones and K speakers are generally installed in the apparatus 200 for enhancing voice transmission according to the present invention, and FIG. 5 is M=4, K=6 in FIG. In the case of , a diagram for explaining the relationship between a microphone and a speaker in a vehicle.

That is, in FIG. 4, when M=4 and K=6, P(z) has a total of 6x4=24 P(z) paths, and the echo canceling unit 210 corresponding to each P(z) Echo cancellation module (AEC), although only one is shown in FIG. 4 for convenience, 6x4=24 are provided.

_{As an echo flows into the left microphone 111 through the two paths P 11} and P ₂₁ corresponding to the two speakers in FIG. 3 and is combined with the voice signal and the noise signal, also in the case of FIG. 4, one microphone With respect to (110), K echoes are introduced into each microphone 110 through K paths P(z) corresponding to K speakers and are combined with a voice signal and a noise signal.

In addition, in FIG. 3 , the _{signal m 1} (n), which is the sum of the voice, noise, and each echo, coming from the left microphone 111 for the cancellation of each of the echoes introduced through _{P 11} and P _{21 is two echo cancellation modules AEC 11} As the noise was suppressed through the _{noise suppression module NS 1} after each echo was removed through , AEC _{21, in the case of FIG.} 110), the voice, the noise and the respective echo signals are summed m _m (n) are each of the echo through the echo canceller AEC module _{1m, 2m} AEC, ... AEC _Km of the K single echo rejection 210 come into After removal, noise suppression is performed through the m-th noise suppression module NS _{m of the noise suppression unit 220 .}

For the M signals that are finally generated through the M NS modules of the noise suppression unit 220 matching the microphone number and have undergone echo cancellation and noise suppression, a speaker to be finally output must be selected. In the case of FIG. 3 , the signal from the first microphone 111 is output to the second speaker 122 , and the signal from the second microphone 112 is matched to be output to the first speaker 121 . However, in a structure in which a general number of microphones and speakers are combined, a configuration for such a matching is required. In the present invention, as shown in FIG. 4 , a gain matrix application unit 250 is provided to perform this. The role of the gain matrix application unit 250 is to output an input signal of a specific microphone to a speaker located close to the occupant far from the microphone.

로 구성될 수 있다. 이때 도 4에서 NS₁, NS₂를 거친 최종 마이크 신호를 fm₁, fm₂라 하면, 1번 스피커로 출력되는 신호 y₁ 및 2번 스피커로 출력되는 신호 y₂는 각각, For example, if M=2, K=2, the gain matrix is

can be composed of At this time, if the final microphone signal that has passed through _{NS 1} and NS _{2 in FIG. 4 is fm 1} , fm ₂ , the signal y ₁ output to the first speaker and the signal y ₂ output to the second speaker are, respectively,

As,

y ₁ = fm ₂ ,

y ₂ = fm ₁

, which has the same configuration as in FIG. 3 .

로 구성될 수 있다. 이때 도 4에서 각 마이크에 대한 소음억제 모듈인 NS₁, ..., NS₄를 거친 최종 마이크 신호를 fm₁, fm₂, fm₃, fm₄라 하고, 1번 ~ 6번 스피커로 출력되는 신호를 각각 y_1, y_2, y_3, y_4, y_5, y₆ 는 각각, Also, for M=4, K=6, the gain matrix is

can be composed of At this time, in FIG. 4, the final microphone signal that has passed through _{the noise suppression modules NS 1} , ..., NS _{4 for each microphone is referred to as fm 1} , fm ₂ , fm ₃ , fm ₄ , and is output to speakers 1 to 6 The signals y _1, y _2, y _3, y _4, y _5, y ₆ are respectively,

As,

y ₁ = fm ₂ + fm ₃ + fm ₄ ,

y ₂ = fm ₃ + fm ₄ ,

y ₃ = fm ₁ + fm ₃ + fm ₄ ,

y ₄ = fm ₁ + fm ₂ + fm ₄ ,

y ₅ = fm ₁ + fm ₂ ,

y ₆ = fm ₁ + fm ₂ + fm ₃

becomes this

5 is a position of passengers including a driver in the vehicle. Passengers corresponding to microphone numbers 1 and 2 are front seats, passengers corresponding to microphone numbers 3 and 4 are rear seats, and speakers 1 to 6 are shown in FIG. It is a situation installed at the location, and the microphone number (in the case of fm) and the speaker number (in the case of y) of the superscript are the same as the microphone number and speaker number shown in FIG. 5 .

From the above formula, it can be seen that:

Output to speaker 1 (y ₁ ): When one of the 2, 3, 4 microphones speaks

Output to speaker 2 (y ₂ ): When one of the 3 or 4 microphones speaks

Output to speaker 3 (y ₃ ): when one of the passengers speaks from microphones 1, 3, and 4

Output to speaker 4 (y ₄ ): When one of the passengers speaks from microphones 1, 2, and 4

Output to speaker 5 (y ₅ ): when one of the passengers speaks from microphone 1 or 2

Output to speaker 6 (y ₆ ): When one of the passengers speaks from microphone 1, 2, or 3

That is, the voice output to the specific speaker is the voice input into the microphone by the passenger far from the speaker. In this way, by using the gain matrix, it is possible to set how to match the microphone output to each speaker with respect to a different number of microphones and speakers.

In the gain matrix application unit 250 of FIG. 4, each value of the gain matrix is set to 0 or 1 to only perform a function of matching a microphone and a speaker, but in addition to this matching function, a gain may be applied for an output. , which will be described below with reference to FIGS. 6 and 7 .

FIG. 6 is a block diagram illustrating a case in which a gain adjustment unit according to environmental noise level analysis is further provided in the voice transmission enhancing apparatus of FIG. 4 , and FIG. 7 is a gain determination curve according to the environmental noise level it is one drawing

와 같이 적용되며, 이에 의해 각 스피커로의 출력은 g의 이득이 적용된 상태로 출력되게 된다.The noise suppressor 220 updates a noise spectrum existing in a microphone signal in every time frame for noise reduction in each NS module. Since the noise spectrum inside the noise suppressor 220 increases when the surrounding environmental noise is large, and when the noise is low, the noise spectrum becomes small. It is possible to estimate the environmental noise level from the spectrum, and from this environmental noise level, the level setting unit 240 determines an audio output gain g to be output to the speaker, and the determined g is applied to the gain matrix application unit 250 . by the gain matrix

is applied, whereby the output to each speaker is output with a gain of g applied.

When the noise level as shown in Fig. 7 for the stable operation is less than NL_Th _min and kept at the same g (gain) to g _min, and maintaining the greater if g than NL_Th _max by g _max, the range of NL_Th than _min and NL_Th _max or less The higher the environmental noise, the higher the gain of the gain matrix, and the lower the noise, the lower the gain of the gain matrix to automatically adjust the voice level.

The gain matrix application unit 250 may perform such matching of a microphone and a speaker and applying a gain in the manner of a hardware or software program.

8 is a flowchart of a method for enhancing speech delivery performed by the apparatus 200 for enhancing speech delivery according to the present invention.

Since this method for enhancing voice delivery has already been described in detail from the configuration of the device 200 for enhancing voice delivery with reference to FIGS. 2 to 7 , such a process will be briefly described with reference to FIG. 8 .

First, from each microphone in the vehicle, the voice of the passenger, noise, and echo sound from each speaker to the corresponding microphone are summed and input, and the combined signal is received by the voice transmission enhancing device 200 (S801). For the signal thus received from each microphone, echo cancellation is performed (S802). For example, each acoustic echo canceller (AEC) of the echo canceller 210 of the voice transmission enhancement device 200 cancels the echo from each speaker to the corresponding microphone in the signal received by each microphone. It generates echo cancellation signals for each speaker, thereby canceling all echoes from each speaker to the corresponding microphone.

Thereafter, on the microphone signals from which echo signals from all microphones are removed, noise suppression is performed by the noise suppression unit 220 (S803), and the microphone signals on which noise suppression has been performed for each microphone are obtained by a gain matrix application unit ( 250), matching with each speaker is performed using the gain matrix, thereby generating an output signal to each speaker (S806).

In this case, the environmental noise analysis by the noise level analyzer 230 may be performed on the microphone signal on which the noise suppression has been performed. That is, the environmental noise level can be estimated from the noise spectrum present in the microphone signal (S804), and accordingly, the level setting unit 240 determines the audio output gain g (S805), and the determined g is the gain It is applied to the gain matrix by the matrix application unit 250 to match each speaker, and thereby generate an output signal to each speaker (S806).

10: Voice transmission system from the in-vehicle speaker to the microphone
20: sum of voice, noise and echo
100: vehicle
110,111,112: microphone
120,121,122: speaker
200: voice transmission enhancement device
210: echo canceller (acoustic echo canceller, AEC)
211: LMS algorithm execution unit
212: echo cancellation adaptive filter
213: echo cancellation signal sum
220: noise suppressor (noise supperessor, NS)

Claims (15)

As an in-vehicle voice transmission reinforcement device,
an echo canceling unit for receiving a sum signal of voice input from a corresponding microphone, noise, and an echo from the speaker to the corresponding microphone with respect to each microphone provided in the vehicle, and removing the echo therefrom; and,
For each of the microphones, a noise suppressor that performs noise suppression on the signal from which the echo is removed
including,
If the vehicle is equipped with M microphones and K speakers,
The echo canceling unit,
Corresponding to each of the M microphones, provided with M x K acoustic echo canceller (AEC) modules for canceling K echoes introduced in the path from the K speakers to the corresponding microphone,
The noise suppression unit,
Corresponding to each of the M microphones, it includes M noise suppressor modules that perform noise suppression on a signal from which echo is removed,
A gain matrix application unit for matching M microphone signals for which noise suppression has been performed by the noise suppression unit and a speaker to which each signal is to be output by using a gain matrix
further comprising,
In-vehicle voice transmission enhancement device.
delete The method according to claim 1,
Each of the echo cancellation modules,
an echo cancellation adaptive filter for generating an echo cancellation signal for canceling the echo from a signal in which voice, noise, and echo are summed; and,
An LMS algorithm performing unit that updates the echo cancellation adaptive filter through the LMS algorithm using the echo cancelled, sum signal of voice and noise and the speaker output signal
In-vehicle voice transmission enhancement device, characterized in that it comprises a.
delete The method according to claim 1,
The gain matrix application unit,
A function of setting an audio output gain for output to a speaker with respect to the microphone signal on which the noise suppression has been performed
In-vehicle voice transmission enhancement device, characterized in that it further comprises. 6. The method of claim 5,
a noise level analyzer for estimating an environmental noise level from a noise spectrum in the noise suppressor; and,
A level setting unit that determines an audio output gain to be output to a speaker from the estimated environmental noise level
In-vehicle voice transmission enhancement device, characterized in that it further comprises. 7. The method of claim 6,
The level setting unit,
Determining the gain level in such a way that the greater the estimated environmental noise, the higher the gain of the gain matrix, and the lower the noise, the lower the gain of the gain matrix.
In-vehicle voice transmission enhancement device, characterized in that. 8. The method of claim 7,
When the environmental noise level is smaller than a specific value (hereinafter referred to as a 'first reference level'), the gain is maintained at a preset specific value (hereinafter referred to as a 'first gain level'), and the environmental noise level is a different specific value (hereinafter referred to as a 'first gain level') (hereinafter referred to as 'second reference level'), maintaining the gain at another predetermined specific value (hereinafter referred to as 'second gain level')
In-vehicle voice transmission enhancement device, characterized in that. A method for enhancing voice transmission inside a vehicle, comprising:
(a) with respect to each microphone provided in the vehicle, receiving a signal of the sum of the voice input to the microphone, noise, and the echo from the speaker to the corresponding microphone, and removing the echo therefrom; and,
(b) for each of the microphones, performing noise suppression on the signal from which the echo is removed
including,
After step (b),
(c) performing matching of each microphone signal on which the noise suppression has been performed and a speaker to which each signal is to be output by using a gain matrix
further comprising,
A method for enhancing voice transmission inside a vehicle. 10. The method of claim 9,
Upon canceling the echo,
For each microphone received signal, removing each echo introduced in the path from each speaker to the corresponding microphone,
that the noise suppression is performed for each of the echo-removed signals
In-vehicle voice transmission enhancement method, characterized in that. delete 10. The method of claim 9,
Before performing the matching in step (c),
(c0) setting an audio output gain for output to a speaker with respect to the microphone signal on which the noise suppression has been performed
In-vehicle voice transmission enhancement method, characterized in that it further comprises. 13. The method of claim 12,
The step (c0) is,
(c01) estimating an environmental noise level from a noise spectrum measured during noise suppression; and,
(c02) determining an audio output gain to be output to a speaker from the estimated environmental noise level
In-vehicle voice transmission enhancement method comprising a. 14. The method of claim 13,
The audio output gain is
The gain level is determined by increasing the gain of the gain matrix as the estimated environmental noise increases, and decreasing the gain of the gain matrix as the noise decreases
In-vehicle voice transmission enhancement method, characterized in that. 15. The method of claim 14,
When the environmental noise level is smaller than a specific value (hereinafter referred to as a 'first reference level'), the gain is maintained at a preset specific value (hereinafter referred to as a 'first gain level'), and the environmental noise level is a different specific value (hereinafter referred to as a 'first gain level') (hereinafter referred to as 'second reference level'), maintaining the gain at another predetermined specific value (hereinafter referred to as 'second gain level')
In-vehicle voice transmission enhancement method, characterized in that.

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