HK1114294B - Method of correction of acoustic parameters of electro-acoustic transducers and device for its realization - Google Patents

Description

Method for correcting acoustic parameters of electroacoustic transducer and device for implementing same

Technical Field

The present invention relates to the field of acoustics, and more particularly to a method and apparatus for modifying acoustic parameters of an electroacoustic transducer, which may be used to improve playback parameters of acoustic signals of various electroacoustic transducers.

Background

The known devices and methods use the measurement of acoustic parameters of an electroacoustic transducer for correcting the acoustic parameters of the electroacoustic transducer, wherein the correction is performed automatically and by the involvement of an operator. The disadvantages of this known solution are a relatively low measurement accuracy and a poor quality of the correction result.

It is known that the human ear perceives information about the timbre of sound from direct sound, i.e. sound directly from the acoustic transducer and early reflections of sound that arrive at the listener within 30 milliseconds after the arrival of the direct sound, while ignoring other reflections of sound. The measuring devices used up to now do not distinguish and separate direct sound waves and early sound wave reflections from later sound wave reflections.

Wherein the known solution for correcting acoustic parameters of electro-acoustic transducers is based on an evaluation of the sound pressure caused by the electro-acoustic transducer and does not reflect the real problem of the reproduction of the electro-acoustic transducer. Furthermore, when changing the evaluation position of the sound pressure generated by the electroacoustic transducer, the frequency response of the sound pressure varies greatly at each position, which leaves the operator with unsolvable questions-of how to use the acquired sound pressure frequency response, and how to manually correct or differentiate additional parameters. The process uses a similar technique since there is no dedicated algorithm for implementing the correction. When these measurements are used to correct the acoustic parameters of the electro-acoustic transducer, new sound distortions are created, since it is the representation of the acoustic wave interference at a specific location in space that is sought to be corrected in the known solutions. Therefore, the correction of the acoustic parameters of the electroacoustic transducer is incorrect and insufficient for transmission distortions and inconsistencies of the electroacoustic transducer.

There is known a Method of measuring parameters of a speaker (U.S. Pat. No. 4,209,672, "Method and apparatus for measuring characteristics of sound," 20.6.1980, international patent classification (2 nd edition) H04R 29/00), according to which a measurement result of a parameter of a perceivable sound is converted from an analog form into a digital form, the resultant is fourier-transformed, and then modified into an absolute value, logarithmized, and further filtered to eliminate the influence of interference, thereby increasing the accuracy of the measurement of the speaker parameters. Finally, the result is converted to analog form and written to memory accordingly. Wherein the result is written repeatedly by replaying the test signal from the generator at certain time intervals. The disadvantages of the method presented are: the adjustment is made using measurements that do not reflect the sound distortion of the electro-acoustic system, and the filtering process does not distinguish between sound distortion produced by the electro-acoustic system and sound distortion produced by the space. Thus, the calculated adjustment is inaccurate and the adjustment results produce worse sound than before the adjustment.

An acoustic signal modification apparatus (U.S. Pat. No. 5,581,621, "Automatic adjustment system and Automatic adjustment method for audio devices", 1996 3/12, international patent classification (6 th edition) H03G 5/00) is known, which comprises a memory device for holding equalizer data, an audio device with a programmable equalizer which selectively modifies an audio signal according to the equalizer data, and an audio signal analyzer which generates a staircase (bench) signal which compares an output signal of audible sound with a pattern profile (pattern profile) of a preferred frequency response stored in its memory. Wherein the signal analyzer is connected to the programmable equalizer and the audio device, and the audio device generates an audible sound signal corresponding to the staircase signal. The acoustic signal correction device further includes a tool for performing automatic equalizer data correction based on the comparison result. The memory device stores the frequency response pattern profile and the adjustment results in the memory. The equalizer also contains means for dividing the output signal into sub-ranges of a plurality of frequencies. The disadvantages of the ranges given are: the use of measurements that do not reflect the sound distortion of the electro-acoustic system for acoustic signal correction results in a poorer sound produced by the adjustment than before the adjustment.

The closest solution, assumed as a prototype, is an Acoustic feature correction device (european patent No. 0624947, "Acoustic characteristic correction device" on 8/27/2003, international patent classification (7 th edition) H03G 5/16), in which known devices include:

a measurement module comprising a measurement unit, the measurement unit comprising: a signal source having a test signal written in a memory, an amplifier, a reproducing device, a measuring device, a signal-under-test amplifier, a memory for fixing a signal received from the measuring device, and a processing section for determining a correction parameter;

and a correction module including a control unit having the correction parameters written in the memory and an implementation module for inputting the required parameters.

By making corrections zone by zone, the frequency range is partitioned zone by zone, providing the best parameters for a specific requirement, where each zone is connected end to end. The known device has the disadvantage of limited functional options, insufficient measurement accuracy of the electroacoustic transducer and relatively poor sound quality of the corrected reproduced signal. The sound comparison difference of the corrected playback signal is related to the following facts: the correction feature definition is not accurate because, firstly, the measurement results of the used correction acoustic signals do not reflect the real problem of the sound quality perceived by the listener; secondly, the proper correction parameters are subjectively evaluated through the participation of an operator, which causes the objectivity of correction to be questioned; third, the known technical solution intends to divide the frequency range into relatively wide regions, which reduces the number of samples on the frequency axis, thus making the information on the characteristic variation of the frequency response on the frequency axis inaccurate.

Disclosure of Invention

The aim of the invention is to improve the reproduction quality of the acoustic signals of various electroacoustic transducers, to improve the accuracy and speed of the correction of the acoustic parameters of the electroacoustic transducers associated therewith, and to improve the effectiveness of the automatic correction with a minimum of operator involvement.

The set object is achieved by a method for correction of acoustic parameters of an electro-acoustic transducer, the method comprising measuring acoustic parameters of the electro-acoustic transducer on a peripheral surface of the electro-acoustic transducer or a part thereof, obtaining measurement results from a plurality of discrete points of the surface or the part, processing the obtained measurement results, calculating an acoustic power frequency response of the electro-acoustic transducer from the processed acoustic parameter measurement results of the electro-acoustic transducer, determining the correction parameters of the electro-acoustic transducer using the acoustic power frequency response of the electro-acoustic transducer and an acoustic signal correction.

The set target may also be achieved by:

obtaining an estimate of the acoustic power frequency response of the electro-acoustic transducer by continuously moving the measuring device from one discrete point to another discrete point of the peripheral surface of the electro-acoustic transducer, making measurements at intervals of 0.2-3.2 seconds, and using a test signal having a duration in the range of 0.05-3.2 seconds;

the location of evaluating the frequency response of the acoustic power of the electroacoustic transducer is mainly the lower horizontal reflecting surface, the acoustic parameters of the electroacoustic transducer are measured on a part of the peripheral surface of the electroacoustic transducer, one side of the peripheral surface is in contact with the lower horizontal reflecting surface, wherein the measuring surface is perpendicular to the direction in which the electroacoustic transducer to which the measured parameters belong is directed;

in order to obtain an assessment of the acoustic power frequency response of an electroacoustic transducer at a site having a plurality of major surfaces, measurements are taken along a line connecting an arbitrarily selected point on a lower horizontal acoustic environment reflective surface to an arbitrarily selected point on each of the other acoustic environment reflective surfaces;

in order to obtain an estimate of the acoustic power frequency response of the electroacoustic transducer at a site where the surface structure is complex, measurements are taken along a virtual circular line lying in a vertical plane through the direction in which the electroacoustic transducer is pointing, and along the horizontal and vertical diameters of the virtual circular line;

in order to obtain an estimate of the acoustic power frequency response of an electroacoustic transducer in a small space with parallel walls, measurements are made in the space diagonally from the center of symmetry of the space to the corner furthest from the electroacoustic transducer.

Processing each specific discrete measured impulse response by a window function, wherein the width of the window function is selected in the range of 0.04-0.12 seconds;

smoothing an evaluation of an acoustic power frequency response of the electro-acoustic transducer on a logarithmic frequency scale; wherein the evaluation of the acoustic power frequency response is smoothed by a smoothing function of the cosine pulse.

The set object is also achieved by providing a device for realizing a parameter modification of an acoustics of an electroacoustic transducer (see claim 11), the device comprising:

a measurement system comprising a measurement unit, a measurement processing unit for determining a correction parameter, and an interface module, wherein the measurement unit comprises: a signal source for generating a test signal having the test signal written in the memory, an amplifier for reproducing the test signal, a measuring device, an amplifier for a signal to be measured, a memory for recording a signal received from the measuring device, and an output of the measuring unit;

and a corrector including a control unit having a correction parameter written in the memory and a correction implementation module, wherein the measurement processing unit includes: the impulse response calculation module is used for carrying out convolution operation between an output signal of the measuring system and the inverse spectrum function module for calculating the impulse response; a window function module for multiplying samples of the impulse response signal with samples of a window function to exclude the effect of the interference component; a fast fourier transform module for computing a fast fourier transform from the impulse response signal, thereby defining an array of frequency sample data for each individual impulse response; a synchronization module for synchronizing a start point of the fast fourier transformed input data with a highest value of the impulse response; a memory for storing a data array of frequency samples; an acoustic power frequency response calculation module for calculating an acoustic power frequency response from the array of frequency sample data; a resampling module for transforming the acoustic power frequency response from a linear scale to a logarithmic scale; a display for displaying the calculated acoustic power frequency response; means for defining a modification level for a range endpoint of an acoustic power frequency response; the acoustic power frequency response equalization module is used for eliminating the influence of slight irregularity and interference of the acoustic power frequency response; a resampling module to transform the power frequency response from a logarithmic scale to a linear scale; an inverter for calculating a value of an inverse of the power frequency response samples; a power frequency response sample filtering module for obtaining a total impulse response of the modifier; and an inverse fast fourier transform calculation module for calculating a modified impulse response sample and sending the data to a normalized sample calculation module of the impulse response, wherein the realization module performs a convolution operation between an input signal of the sound signal and the modified impulse response from the control unit and sends the obtained calculation result to the sound signal output.

In addition, the apparatus may further include: means for calculating an average of the synchronization impulse responses; means for calculating a group time delay; a group delay equalization module; means for calculating a phase modifier frequency response from the time delay frequency response; and adjusting a phase of the acoustic power frequency response by multiplying each sample of the acoustic power frequency response with each sample of the acoustic power frequency response in complex form. The apparatus may further comprise a plurality of modifiers.

Drawings

A method of modifying acoustic parameters of an electro-acoustic transducer and apparatus for implementing the method are described in the accompanying drawings, in which:

FIG. 1A depicts an alternative discrete point distribution scheme for measuring acoustic parameters of an electroacoustic transducer at a site having a major, low horizontal reflective surface;

FIG. 1B depicts an alternative discrete point distribution scheme for measuring acoustic parameters of an electroacoustic transducer at a site having a plurality of primary reflective surfaces;

FIG. 2A depicts an alternative discrete point distribution scheme for measuring acoustic parameters of an electroacoustic transducer in a small space with parallel walls;

FIG. 2B depicts an alternative discrete point distribution scheme for measuring acoustic parameters of an electroacoustic transducer at a site having a complex structured reflective surface;

FIG. 3 depicts test signal waveforms;

fig. 4 depicts a general block diagram of an electroacoustic transducer acoustic parameter modification apparatus;

fig. 5 depicts a detailed block diagram of the measuring unit of the measuring system of the electroacoustic transducer acoustic parameter correction device;

fig. 6 depicts a detailed block diagram of the measurement processing unit of the measurement system of the electroacoustic transducer acoustic parameter correction device;

FIG. 7 depicts an acoustic power frequency response indicating an amplification/attenuation point;

fig. 8 depicts the smoothed acoustic power frequency response.

Detailed Description

The correction of acoustic parameters of an electroacoustic transducer is carried out with the apparatus shown in fig. 4, which consists of a measuring system 1 comprising a measuring unit 3, a measurement processing unit 4 and an interface module 5, and at least one corrector 2, which corrector 2 comprises a control unit 6, an implementation module 7 with a sound signal input 8 and a sound signal output 9. The acoustic parameters of the electroacoustic transducer are modified as follows:

a schematically represented signal source 10 (fig. 5) with an acoustic test signal written in memory repeatedly replays a test signal whose spectrum is comparable to the interference spectrum at the measurement site. Therefore, the test signal is selected to have a spectrum with higher energy in a low frequency region, in which the interference energy is higher, and so as to have a maximum value sufficiently small with respect to the average value. In an example of implementation of the invention, the signal is chosen such that a signal-to-noise ratio in the range of 20-30dB can be obtained. The duration of the played test signal is selected to be 0.05 seconds.

Furthermore, the played-back acoustic test signal is amplified by means of an amplifier 11 and played back by means of a modifiable electroacoustic transducer 12. The measuring device 13 senses the acoustic test signal played by the electro-acoustic transducer at time intervals of 0.4 seconds at discrete points of the surrounding acoustic environment. Therein, as schematically shown in fig. 1A, measurement is performed on a portion of the peripheral surface of the electroacoustic transducer by moving the measuring device uniformly from one measuring point to another measuring point. When measuring parameters of an electroacoustic transducer in a space having a plurality of asymmetrically placed primary reflecting surfaces, the measuring device is moved along a line connecting a point on the ground of each space and a point on the primary reflecting surface, as shown in fig. 1B. When measuring parameters of the electroacoustic transducer in a space having parallel walls, the measuring device is diagonally moved from the center of symmetry to the corner of the space farthest from the electroacoustic transducer (see fig. 2A). When the parameters of the electroacoustic transducer are measured in a space where the structure of the reflecting surface is complicated, or when the measurement becomes complicated by an object existing in the space, the measuring device is moved along a virtual circular route located in the vertical plane through the direction in which the electroacoustic transducer is directed and along the horizontal diameter and the vertical diameter of the virtual circular route, as shown in fig. 2B.

Furthermore, the acoustic test signals sensed by the measuring device 13 are passed through an amplifier 14 into a memory 15, all the signals obtained at the respective measuring points being input into the memory 15 and then through an output 16 into an input 17 of the measurement processing unit 4 for calculating the correction filter parameters (fig. 6). The signal then enters an impulse response calculation module 18 for performing a convolution operation between the output signal 4 of the measurement unit and the inverse spectral function stored in the spectral inversion module 19, the module 18 being arranged to calculate an impulse response for the electroacoustic transducer at each measurement point. The signal then enters a window function block 20 to remove distortion factors such as non-linearities and reflection effects. The window function block 20 multiplies the impulse response signal samples with window function samples stored in a memory of the block 21.

The window function is used so that it is 1 at the highest value of the impulse response and tends to 0 at the lowest value of the impulse response, thereby rejecting interference factors such as non-linearity and reflections from the measurement results. The longer the time of the window function, the larger the difference of the measurement results in the low frequency region, resulting in an increased influence of the reflection. As the window function time is shortened, although the information of the low frequency region starts to disappear, the influence of the space is also reduced.

After signal processing in the window function block 20, the result is passed to a fast fourier transform block 22 which computes a fast fourier transform from the impulse response signal to determine an array of frequency samples for each individual impulse response, and the start of the input array of fast fourier transforms is synchronized with the highest value of the impulse response in a synchronization block 23. The resulting data is then entered into a memory 24 storing an array of frequency samples, the acoustic power frequency response is calculated in a block 25, which calculates the acoustic power frequency response from the above-mentioned array of frequency samples, and the acoustic power frequency response is converted from a linear frequency scale to a logarithmic frequency scale in a resampling block 26. The calculated acoustic power frequency response is displayed in the display 27. The calculation then proceeds to block 28 which determines the correction level for the end of the range of the acoustic power frequency response (see fig. 8). The low frequency region (L) is selected based on the ability of the modifiable electroacoustic transducer to reproduce low and high frequency signals without overload_LF) And high frequency region (L)_HF) The end of range correction level. In an example of implementing the present invention, the correction level of the end point of the range is in the low frequency regionThe-5 dB is selected and the-6 dB is selected in the high frequency region.

The calculation then proceeds to an acoustic power frequency response smoothing module 29 and a resampling module 30, the module 29 being used to remove the effects of slight irregularities and interference of the acoustic power frequency response (see fig. 8), and the module 30 being used to convert the power frequency response from a logarithmic scale to a linear scale. Furthermore, before the fast fourier transform block 22, the result obtained also enters a block 31 for calculating the mean value of the synchronization impulse response and sending it to a block 32 for calculating the group delay time, a block 33 for group delay smoothing, a block 34 for calculating the phase frequency response of the modifier 2 from the group delay time frequency response, and a block 35, the block 35 modifying the acoustic power frequency response phase by multiplying each acoustic power frequency response sample by each phase frequency response sample in complex form and then sending it to an inverter 36 for calculating the value of the inverse of the acoustic power frequency response sample. The result is then sent to a power frequency response sample filter block 37 for obtaining the total impulse response of the modifier 2 and subsequently to an inverse fast fourier transform calculation block 38 for calculating impulse response samples of the modifier 2 and sending the data to an impulse response normalisation sample calculation block 39 and the measurement processing unit 4, exit 4. The acquired data array is further sent to an interface module 5 for saving the impulse response sample array received from the processing unit and then to the control unit 6 of the modifier 2 for saving the different modified impulse responses. The result obtained is passed from the control unit 6 to the implementation module 7 for performing a convolution operation between the signal of the sound signal input 8 and the modified impulse response received from the control unit 6. The correction result is then fed to the sound signal output 9, from which sound signal output 9 the correction result is sent to the amplifier and the respective electroacoustic transducer for reproduction.

By modifying the electroacoustic transducer with the provided method and apparatus, a constant transmission coefficient between the input signal of the modifier and the reflected acoustic power of the electroacoustic transducer at different operating frequencies is achieved. Furthermore, undistorted power is provided for acoustic power transmitted from a source of the acoustic signal, and deep correction of tonal distortion of the electro-acoustic transducer does not create new sound defects, so that natural sound without tonal distortion can be obtained when operating under different conditions and at different locations.

Claims (12)

1. A correction method of acoustic parameters of an electroacoustic transducer, comprising measuring acoustic parameters of the electroacoustic transducer, processing the measurement results, specifying correction parameters of the electroacoustic transducer, and correcting an acoustic signal based on correction characteristics of the calculated acoustic parameters of the electroacoustic transducer, characterized in that: determining a correction parameter of the electro-acoustic transducer by using an electro-acoustic transducer acoustic power frequency response representing a characteristic of the electro-acoustic transducer, the acoustic power frequency response estimate being obtained by taking measurements from a plurality of discrete points on a peripheral surface surrounding the electro-acoustic transducer or on a portion thereof, wherein the correction parameter of the electro-acoustic transducer has a characteristic of an inverse of the acoustic power frequency, wherein the played acoustic test signal spectrum matches the interference spectrum at the test location.

2. Method for the correction of acoustic parameters of electro-acoustic transducers according to claim 1, characterized in that: said evaluation of the acoustic power frequency response of the electroacoustic transducer is obtained by moving the measuring device from one discrete point to another on the peripheral surface of the electroacoustic transducer, the measurements being carried out at intervals of 0.2-3.2 seconds and using a test signal having a duration in the range of 0.05-3.2 seconds.

3. Method for the modification of acoustic parameters of an electroacoustic transducer according to claim 1 or 2, characterized in that; an evaluation of the acoustic power frequency response of the electroacoustic transducer is obtained at a location where the lower horizontal reflecting surface is dominant, said measurement being performed on a part of the entire peripheral surface of the electroacoustic transducer, which surface is in contact on one side with said lower horizontal reflecting surface, wherein the measuring surface is perpendicular to the direction in which the electroacoustic transducer to which the measured parameter belongs is directed.

4. Method for the modification of acoustic parameters of an electroacoustic transducer according to claim 1 or 2, characterized in that; an assessment of the electroacoustic transducer acoustic power frequency response is obtained at a site having a plurality of major surfaces by taking measurements along a line connecting an arbitrarily selected point on the reflective surface of the lower level acoustic environment with an arbitrarily selected point on the major reflective surface of each of the other acoustic environments.

5. Method for the modification of acoustic parameters of an electroacoustic transducer according to claim 1 or 2, characterized in that; an evaluation of the electroacoustic transducer acoustic power frequency response is obtained from a portion of the electroacoustic transducer peripheral surface, at a site having a complex structured surface, by measuring along a virtual circular line lying in a vertical plane through the direction in which the electroacoustic transducer is pointing and along the horizontal and vertical diameters of said virtual circular line.

6. Method for the modification of acoustic parameters of an electroacoustic transducer according to claim 1 or 2, characterized in that; in a space with parallel walls, in which measurements are made diagonally from the centre of symmetry to the corner furthest from the electroacoustic transducer to which the parameter under test belongs, an evaluation of the electroacoustic transducer acoustic power frequency response is obtained from a portion of the electroacoustic transducer peripheral surface.

7. Method for the correction of acoustic parameters of an electroacoustic transducer according to claim 1 or 2, characterized in that: in order to reduce the reflection influence caused by the reflecting surface of the acoustic environment, the impulse response of each specific discrete measurement is processed by a window function.

8. Method for the modification of acoustic parameters of electro-acoustic transducers according to claim 7, characterized in that: the width of the window function is chosen within the range of 0.04-0.12 seconds.

9. Method for the correction of acoustic parameters of an electroacoustic transducer according to claim 1 or 2, characterized in that: the evaluation of the acoustic power frequency response of the electro-acoustic transducer is smoothed in a logarithmic frequency scale.

10. Method for the modification of acoustic parameters of an electroacoustic transducer according to claim 9, characterized in that: the evaluation of the frequency response of the acoustic power of the electroacoustic transducer is smoothed by the cosine pulse averaging smoothing number.

11. A correction device for implementing a correction method for acoustic parameters of an electroacoustic transducer, the correction device consisting of a measurement system and at least one corrector, wherein the measurement system comprises a measurement processing unit and an interface module, the measurement processing unit comprising a signal source for reproducing a test signal written in a memory, an amplifier for reproducing the signal, a measurement device, an amplifier for a signal received from the measurement device, a memory for recording the signal received from the measurement device, a measurement processing unit output for inputting the signal under test into the measurement processing unit for determining correction parameters, the corrector comprising a control unit having a memory in which correction parameters have been written, an implementation module for implementing the correction, characterized in that the measurement processing unit (4) further comprises:

an impulse response calculation module (18) for performing a convolution operation between the output signal of the measurement processing unit (4) and an inverse spectral function for calculating an impulse response stored in the spectral inversion module (19);

a window function block (20) for multiplying the samples of the impulse response signal with the samples of the window function stored in the storage block (21) to cancel the effect of the interference component;

a fast fourier transform module (22) for computing a fast fourier transform from the impulse response signal to determine an array of frequency samples for each individual impulse response;

a synchronization module (23) for making the start of the fast fourier transform input array the same as the highest value of the impulse response;

a memory (24) for storing an array of frequency samples;

an acoustic power frequency response calculation module (25) for calculating an acoustic power frequency response from the array of frequency samples;

a resampling module (26) for transforming the acoustic power frequency response from a linear frequency scale to a logarithmic frequency scale;

a display (27) for displaying the calculated acoustic power frequency response;

an acoustic power frequency response smoothing module (29) for removing the effects of slight irregularities and interferences of the acoustic power frequency response;

a resampling module (30) for transforming the power frequency response from a logarithmic scale to a linear scale;

an inverter (36) for calculating a value of an inverse of the power frequency response samples;

a power frequency response sample filtering module (37) for obtaining a total impulse response of the modifier (2);

an inverse fast fourier transform calculation module (38) for calculating impulse response samples of the modifier (2) and transmitting data;

an impulse response normalized sample calculation module (39) for receiving the data sent by the corrector (2); and

a measurement processing unit output (40);

the implementation module (7) performs convolution between the signal of the sound signal input (8) and the modified impulse response from the control unit (6), and sends the received calculation result to the sound signal output (9).

12. The apparatus for modifying an acoustic parameter of an electroacoustic transducer of claim 11, further comprising:

a first module (31) for calculating an average of the synchronized impulse responses;

a second module (32) for calculating a group time delay;

a third module (33) for group time delay equalization;

a fourth module (34) for calculating a modifier phase frequency response from the group time delay frequency response; and

a fifth module (35) for modifying the phase of the acoustic power frequency response by multiplying each sample of the acoustic power frequency response with each phase frequency response sample in complex form.