JPH0993166A - Loudspeaking information communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress incidence probability of howling by inserting a line loss suitable for an impulse response characteristic so as to eliminate a reverberation component. SOLUTION: An acoustic evaluation signal caused by an evaluation signal generator 12 is sent under the operating environment by a reception signal output terminal 2. The acoustic evaluation signal receives the effect of an acoustic characteristic under external environment and inputted to the inside of the system from a transmission signal input terminal 4. The received acoustic replay signal is subjected to convolution arithmetic operation processing with a waveform of inverse characteristic to the acoustic evaluation signal by a high speed product sum arithmetic circuit 13. The impulse response characteristic of the acoustic space is obtained by the arithmetic processing and an impulse response characteristic evaluation device 14 calculates a square power change quantity in the acoustic impulse response and the quantity of the insertion loss of the circuit loss controller 15 is decided depending on the quantity of the square power change for a period set in the inside of the impulse response characteristic evaluation device 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a communication line, a room sound field control device and a high quality voice communication conference device, and an acoustic echo in which a signal of a receiving path appears in a transmitting path through an acoustic echo path. The present invention relates to a loudspeaker information communication system using an acoustic echo canceller that removes components.

[0002]

2. Description of the Related Art Generally, an acoustic echo canceller is used in a long distance telephone line using a communication satellite and a submarine cable.
It can be roughly divided into one that removes reflection caused by impedance mismatch of the line-to-four-line converter and one that removes reverberation due to acoustic coupling of speaker's voice in a loudspeaker telephone such as a video conference system. It is composed of a variable coefficient filter and a subtraction circuit that generate pseudo-acoustic echo. The basic operation of the acoustic reverberation removing device will be described below.

FIG. 6 is a diagram showing the basic structure of an acoustic echo canceller. The reception signal input terminal 1 is connected to the reception signal output terminal 2, and the reception signal of the reception signal input terminal 1 is branched and supplied to the variable coefficient filter 3 to generate a pseudo acoustic echo. The transmission signal from the transmission signal input terminal 4 and the pseudo acoustic reverberation output from the variable coefficient filter 3 are input to a subtraction circuit 5, where the acoustic reverberation component in the transmission signal is removed, and the output of the subtraction circuit 5 is It is output to the transmission signal output terminal 6. The output of the transmission signal output terminal 6 and the signal of the reception signal input terminal 1 are input to the correction amount calculation circuit 7, and the filter coefficient of the variable coefficient filter 3 is corrected by the output of the coefficient correction amount calculation circuit 7. The reception signal is input to the reception signal input register 8 in the variable coefficient filter 3, and the sum of products of the reception signal of the reception signal input register 8 and the pseudo impulse response of the pseudo impulse response register 9 is obtained by the sum of products circuit 10. Sum of products circuit 10
Is output as a pseudo acoustic echo. The reception signal output terminal 2 and the transmission signal input terminal 4 are connected to a two-wire / four-wire converter for a long-distance telephone line, and to a speaker and a microphone for a loudspeaker system.

Assuming that the signal propagation characteristic of the acoustic echo path is linear and represented by an FIR type digital filter, if the impulse response h (t) and the input received signal x (t) are used, the sampling time interval is Is T, and the acoustic echo y _{k at} time kT is represented by y _k = h ^T x _k (1). Here, h = [h ₁ , h ₂ ,..., H _n ] ^T (2) x = [x _k−1 ,..., X _kn ] ^{T T} : Vector transposition.

On the other hand, the estimated value of h at time kT is h
Assuming s _k , the estimated value ys _k of y _k is given by ys _k = hs _k ^T x _K (3). In the acoustic reverberation removing device, when there is an audio signal at the receiving signal input terminal 1 and no acoustic signal exists at the transmitting signal input terminal 4 and only acoustic reverberation exists, the acoustic reverberation operation is performed as an adaptive operation state. This adaptive operation algorithm generally includes a learning identification method (Atsuhiko Noda, Jinichi Nagumo: “System Learning Identification Method”, Measurement and Control, 7, 9, pp. 597-605 (196
8)) is adopted. The sequential correction of hs _k by the learning identification method is performed by hs _{K + 1} = hs _K + α (x _K e _K ) / x _K ^T x _k (4). However, the e _k = y _k -ys _k, is 0 <α ≦ 1 (5) e k is referred to as residual acoustic echo. Such a calculation operation is performed in the coefficient correction amount calculation circuit 7. The contents of the pseudo impulse response register 9 include a variable coefficient series h.
_sk is stored. α is a coefficient updating gain for determining the sensitivity of estimation, and the closer the correction gain is to 1.0, the greater the amount of correction can be given, and high-speed acoustic reverberation can be removed. It is necessary to change and set according to the line condition. The actual situation is that the determination of the coefficient update gain α currently depends on empirical rules. The coefficient update gain α may be variably controlled according to the magnitude of the residual acoustic reverberation, or may be set according to the indoor characteristics (for example, Shoji Makino, Norio Koizumi: "Adaptive performance of the Eco-Canceller in the indoor sound field" On the improvement of ", IEICE (A), J71-A, 12, pp.2212-2214 (1988-12)).

[0006]

The adaptive operation algorithm based on the least-squares estimation method such as the learning identification method can exert the maximum estimation performance when the input signal is white noise. However, since the signal that is actually input is a voice signal that has a bias in the spectrum, the target system cannot estimate the acoustic characteristics here, and residual acoustic echo is mixed in the transmitted signal, which improves the communication quality. In addition to the deterioration, in the worst case, the loop gain of the communication line exceeds 0 dB, and the howling probability becomes extremely high. Inserting the line loss, which is applied as a countermeasure, cannot cope with the environment, and on the contrary, causes a large level fluctuation in the line. Therefore, the operating state itself is unstable, and a high quality voice information communication space cannot be provided.

In addition, it is expected that a loudspeaker communication system such as this device will be used in various environments, and it has been difficult to reliably handle such environments.

The present invention has been made in view of the above points, eliminates the above problems, and is excellent in high speed and operational stability.
It is an object of the present invention to provide a loudspeaker information communication system using an acoustic echo canceller that has high adaptive performance and performs acoustic control while always maintaining a large acoustic echo cancellation amount.

[0009]

SUMMARY OF THE INVENTION The present invention is to solve these problems and comprises a reception signal input terminal, a reception signal output terminal, a transmission signal input terminal, and a transmission signal output terminal. A variable coefficient digital filter having a pseudo impulse response register that receives the reception signal of the reception signal input terminal, and the sound of the reception signal input from the reception signal output terminal to the transmission signal input terminal through an acoustic echo path. An acoustic echo canceller in which the coefficient sequence is sequentially updated by a coefficient correction amount calculation circuit is used so as to minimize the residual signal obtained by subtracting the pseudo acoustic echo generated by the variable coefficient digital filter from the echo component. In a loudspeaker information communication system, an evaluation signal generator for generating an acoustic evaluation signal, and the acoustic evaluation signal generated by the evaluation signal generator are transmitted via an acoustic space. A reverberation component is removed by inserting a high-speed product-sum calculation circuit that calculates the impulse response characteristic of acoustic space by adding convolution calculation processing to the response signal input from the signal input terminal, and a line loss that is adapted to the impulse response characteristic. (EN) Provided is a loudspeaker information communication system.

Further, a high-speed Fourier transform device for frequency-converting the impulse response characteristic, and an input / output evaluation device for calculating an average spatial loss from the spatial frequency transfer characteristic which is an output from the high-speed Fourier transform device, A loudspeaker information communication system according to claim 1, wherein the probability of howling occurrence is extremely reduced by determining the input / output level of the communication line using the average space loss as a control value.

Further, by supplying the impulse response characteristic and the spatial frequency transfer characteristic as video information to a user or an installer, it becomes possible to adjust a control value such as the magnitude of the line loss, and the like. A loudspeaker information communication system according to claim 1, which realizes high-quality voice information communication.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a first high-quality loudspeaker information communication system of the present invention. As shown in FIG. 1, according to the present invention, the conventional reception signal input terminal 1, reception signal output terminal 2, variable coefficient digital filter 3, transmission signal input terminal 4, subtraction circuit 5, transmission signal output terminal 6, coefficient correction. A device having the same configuration as the acoustic echo canceling device 11 that employs the learning identification method as an adaptive algorithm configured by the quantity calculation circuit 7, the reception signal input register 8, the pseudo impulse response register 9, and the product-sum calculation circuit 10 is evaluated. The configuration is such that a signal generator 12, a high-speed product-sum calculation circuit 13, an impulse response characteristic evaluation device 14, and a circuit loss control device 15 are added. The reception signal input terminal 1, the reception signal output terminal 2, the transmission signal input terminal 4, the transmission signal output terminal 6, and the pseudo impulse which receives the reception signal of the reception signal input terminal 1 The variable coefficient digital filter 3 having the response register 9 and the variable coefficient digital filter 3 from the acoustic echo component of the reception signal input from the reception signal output terminal 2 to the transmission signal input terminal 4 via the acoustic echo path. In a loudspeaker information communication system using an acoustic echo canceller 11 in which a coefficient sequence is sequentially updated by the coefficient correction amount calculation circuit 7 so as to minimize a residual signal obtained by subtracting the pseudo acoustic echo generated in The acoustic evaluation signal generated by the evaluation signal generator 12 is emitted from the reception signal output terminal 2 to the environment for using the voice information communication system. The acoustic evaluation signal is influenced by the acoustic characteristics in the external environment, and is input from the transmission signal input terminal 4 to the inside of the voice information communication system. The input acoustic response signal is subjected to convolution calculation processing with the waveform having the inverse characteristic of the acoustic evaluation signal in the high-speed product-sum calculation circuit 13. By this arithmetic processing, the impulse response characteristic of the acoustic space is obtained, and in the impulse response characteristic evaluation device 14,
The circuit power loss controller 1 calculates the squared power variation of the acoustic impulse response and determines the magnitude of the squared power variation in a section set inside the impulse response characteristic evaluation device 14.
A high-quality loudspeaker information communication system for determining the size of insertion loss of 5. FIG. 2 is a block diagram showing the configuration of the second high-quality loudspeaker information communication system of the present invention. As shown in Figure 1,
The present invention includes the conventional reception signal input terminal 1, reception signal output terminal 2, variable coefficient digital filter 3, transmission signal input terminal 4, subtraction circuit 5, transmission signal output terminal 6, coefficient correction amount calculation circuit 7, reception signal. The evaluation signal generating device 1 has the same configuration as the acoustic echo canceling device 11 that employs a learning identification method as an adaptive algorithm configured by an input register 8, a pseudo impulse response register 9, and a product-sum operation circuit 10.
2, high-speed product-sum operation circuit 13, high-speed Fourier transform device 1
6, input / output evaluation device 17, and input / output compensation device 18
Has been added. The reception signal input terminal 1
, The reception signal output terminal 2 and the transmission signal input terminal 4
And the transmission signal output terminal 6 and the pseudo impulse response register 9 that receives the reception signal of the reception signal input terminal 1
And the variable coefficient digital filter 3 generated from the acoustic echo component of the received signal input to the transmitted signal input terminal 4 from the received signal output terminal 2 via the acoustic echo path. In a loudspeaker information communication system using an acoustic echo canceling device 11 in which a coefficient sequence is sequentially updated by the coefficient correction amount calculating circuit 7 so as to minimize a residual signal obtained by subtracting pseudo acoustic echo, The acoustic impulse response characteristic output from the product-sum calculation circuit 13 is frequency-converted in the high-speed Fourier transform device 16 to directly calculate the spatial frequency transfer characteristic, and based on this value, the input / output evaluation device 17 zeros. Calculate the average distance between levels. Then, in the input / output compensation device 18,
A high-quality loudspeaker information communication system that determines the compensation level corresponding to the average value of the distance and inserts it into the communication line. Further, it is also possible to adopt a configuration in which the first high-quality loudspeaker information communication system and the second high-quality loudspeaker information communication system are combined. In this case, it is possible to configure high-quality voice communication in which no reverberation component is mixed and a loudspeaker information communication system in which the probability of howling is suppressed to an extremely low level. A high-quality loudspeaker information communication system configured to supply the impulse response characteristic and the spatial frequency transfer characteristic as video information to a user or an installer so that special settings can be made for each environment. The setting values can be determined using this evaluation signal even when the communication line is connected or disconnected, and can be determined automatically or manually. Of course, when the environment is not measured, the high-speed product-sum calculation circuit 13 is controlled so as to stop its operation and allow the transmission signal to pass through as it is.

FIG. 3 is a diagram showing an example of the evaluation signal used in the present invention. This evaluation signal is a time-delayed pulse (for example, Suzuki, Asano, Sone, "Simulation of transfer function of acoustic system (2)", The Acoustical Society of Japan, 45, pp.46.
-50. (1989)) is one of the typical evaluation signals. As the evaluation signal, any signal may be used as long as its accuracy is guaranteed. Therefore, the present invention can be configured without using the one presented here. FIG. 4, FIG. 5, and FIG. 6 show the calculation results at each stage. FIG. 4 shows an output of the high-speed product-sum calculation circuit 13, which is an acoustic impulse response characteristic. This waveform is used as the impulse response characteristic evaluation device 14
FIG. 5 shows the result of calculation of the squared variation amount at. From this evaluation value, the variable coefficient digital filter 3
The amount of reverberation in the non-adaptable area that exceeds the specifications of is calculated and used as an index of the amount of circuit loss. Further, FIG. 6 shows a spatial frequency transfer characteristic in which the waveform of the acoustic impulse response characteristic is frequency-converted by the high-speed Fourier transform device 16. From the waveform of FIG. 6, the input / output evaluation device 17 calculates the average value of the distances from the zero level and passes the value to the input / output compensation device 18.

[0014]

As described above in detail, according to the present invention, the following effects are expected. (1) It is possible to realize a high-quality loudspeaker information communication system that does not cause discomfort even in an environment having a large reverberation time that exceeds the adaptive performance of the acoustic echo canceller.

(2) Since the resultant loss does not have to be inserted into the communication line, the line level can be small,
It is possible to prevent deterioration of sound quality.

(3) In most cases, the external environment in which the acoustic echo removal processing is used far exceeds the performance of the acoustic echo removal processing. Even in such a situation, by using the present invention, it is possible to provide a high-quality loudspeaker information communication system in which the probability of howling is suppressed to an extremely low level.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of a first high-quality loudspeaker information communication system according to the present invention.

FIG. 2 is a block diagram showing a configuration example of a second high-quality loudspeaker information communication system according to the present invention.

FIG. 3 is a diagram showing an example of a time-extended pulse waveform of an evaluation signal used in the description of the present invention.

FIG. 4 is a diagram showing an example of acoustic impulse response characteristics used in the description of the present invention.

FIG. 5 is a diagram showing an example of a square change amount of an acoustic impulse response waveform used in the description of the present invention.

FIG. 6 is a diagram showing an example of frequency-converted spatial frequency transfer characteristics of the acoustic impulse response waveform used in the description of the present invention.

FIG. 7 is a block diagram showing an example of the basic configuration of a conventional acoustic echo canceller.

[Explanation of symbols]

 1 reception signal input terminal 2 reception signal output terminal 3 variable coefficient filter 4 transmission signal input terminal 5 subtraction circuit 6 transmission signal output terminal 7 correction amount calculation circuit 8 reception signal input register 9 pseudo impulse response register 10 sum of products calculation circuit 11 Acoustic echo canceller 12 Evaluation signal generator 13 High-speed product-sum calculation circuit 14 Impulse response characteristic evaluation device 15 Circuit loss control device 16 High-speed Fourier transform device 17 Input / output evaluation device 18 Input / output compensation device

Claims (3)

[Claims] 1. A variable having a reception signal input terminal, a reception signal output terminal, a transmission signal input terminal, a transmission signal output terminal, and a pseudo impulse response register to which the reception signal of the reception signal input terminal is input. A coefficient digital filter and a pseudo acoustic echo generated by the variable coefficient digital filter are subtracted from the acoustic echo component of the reception signal input to the transmission signal input terminal from the reception signal output terminal through the acoustic echo path. In a loudspeaker information communication system using an acoustic echo canceller in which a coefficient sequence is sequentially updated by a coefficient correction amount calculation circuit so as to minimize a residual signal to be obtained, an evaluation signal generation device that generates an acoustic characteristic evaluation signal, The acoustic evaluation signal generated from the evaluation signal generator is subjected to convolution calculation processing to the response signal input from the transmission signal input terminal via the acoustic space. A high-speed product-sum calculation circuit for calculating impulse response characteristics of an acoustic space, and a reverberation component is removed by inserting a line loss adapted to the impulse response characteristics. 2. A high-speed Fourier transform device for frequency-converting the impulse response characteristic, and an input / output evaluation device for calculating an average spatial loss from the spatial-frequency transfer characteristic output from the high-speed Fourier transform device. The loudspeaker information communication system according to claim 1, wherein the probability of occurrence of howling is reduced by determining the input / output level of the communication line using the average space loss as a control value. 3. A control value such as the magnitude of the line loss can be adjusted by supplying the impulse response characteristic and the spatial frequency transfer characteristic as image information to a user or an installer, and a higher value can be obtained. The loudspeaker information communication system according to claim 1, which realizes quality voice information communication.