RU2547166C1 - Method to measure harmonic distortions of electric signal (versions) and device for its realisation - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: in methods of measurements prior to assessment of intensity of higher harmonics they are reduced by the value equal to the value of rising of the audibility threshold curve on their appropriate frequencies in presence of a masking signal with frequency of main harmonic component. In the device for realisation of measurement methods a connection between the output of the second differentiation unit and the input of the control and measurement unit is broken, and between them the unit of frequency processing of the signal is introduced, shunted with the third switch, comprising a band filter and a comparison device, at the same time the input of the threshold filter and the first input of the comparison device are connected together and to the output of the second differentiation unit, the output of the band filter is connected to the second input of the comparison device, and the output of the comparison device - to the input of the control and measurement unit. The band filter comprises a low pass filter tuned by level and a low pass filter tuned by frequency connected by inputs, which with their outputs are connected to different inputs of the summator, besides, the inputs of low and high pass filters form an input of the band filter, and the output of the summator - its output, besides, filters of low and high pass filters are tuned by frequency simultaneously.

EFFECT: increased extent of compliance of results of measurement with subjective perception of distortions and expansion of functional capabilities.

3 cl, 2 dwg

Description

Technical field

The group of inventions relates to the field of instrumentation and is intended to measure the harmonic distortion of an electrical signal introduced by sound equipment, in particular sound reinforcement equipment.

The purpose of the group of inventions is to increase the degree of conformity of the measurement results to the subjective perception of distortion, as well as expanding the functionality of the device.

With regard to measurement methods, this is achieved by reducing the psycho-acoustic redundancy of the distorted signal by formally matching the intensities of the higher harmonics with a quantitative measure of their frequency masking during auditory perception, for which, before assessing, the intensities of the higher harmonics are reduced by an amount equal to the increase in the curve of the threshold of hearing at their respective frequencies in the presence of a masking signal with a fundamental frequency.

Regarding the device for implementing the proposed measurement methods, this is achieved by introducing the capabilities of determining masked harmonics coefficients, masked and weighted harmonics coefficients, masked and double-weighted harmonics coefficients, for which the connection between the output of the second differentiation unit and the input of the control and measurement unit is broken and a block is introduced between them signal processing frequency, shunted by the third switch, containing a band-pass filter and a device in this case, the input of the bandpass filter and the first input of the comparison device are connected together and connected to the output of the second differentiation unit, the output of the bandpass filter is connected to the second input of the comparison device, and the output of the comparison device is connected to the input of the control and measuring unit, while the bandpass filter consists of connected by the inputs of the low-pass filter tunable in level and frequency and the high-frequency tunable high-pass filter, which are connected by their outputs to different inputs of the adder, and the inputs of the ph ters of the lower and upper frequency input form the bandpass filter and the output of the adder - its output, to the same low-pass filters and high-pass frequency rebuilt simultaneously.

Description of analogues

Simulation of the psychoacoustic properties of human hearing is widely used in algorithms for compressing audio information in order to reduce the speed of the digital stream up to the maximum possible values at which data loss does not entail a noticeable loss in sound quality caused by a decrease in the quantization signal-to-noise ratio.

The ability to compress audio data is based on the irrevocably discarding that part of the signal that relates to psychoacoustic redundancy, which means it will not be perceived when listening. Psychoacoustic signal redundancy is associated with various properties of the human auditory system, including masking phenomena in the frequency and time domains of perception. Reduction of psychoacoustic redundancy is used in compression algorithms for audio information of MPEG, ATSC Dolby AC3 standards, etc. [one]. These algorithms use sophisticated processing of digital audio data, carried out according to the results of signal analysis in the block of psychoacoustic modeling of auditory perception. Modeling the fundamental properties of hearing requires the implementation of numerous stages of processing an audio signal using complex hardware and software.

Another approach is possible, which does not require modeling of the properties of hearing, and therefore easier to implement, is to obtain a formal agreement of the measurement results with a quantitative measure of their auditory assessment using a corrective characteristic that has an adequate course of its dependence. So, it is known an analogue compander noise reduction device that compresses and subsequently expands the signal in order to reduce the effect of phonogram noise on sound quality, in principle, the operation of which frequency masking is taken into account [2]. In the encoder of the device on the recording side, frequency processing is used based on a characteristic whose dependence is inversely proportional to the dependence of the curve of the auditory threshold in the presence of a masking noise signal. In the decoder on the playback side, the inverse frequency processing applied to the encoder is applied. This reduces the influence of modulation noise on the quality of reproduction of phonograms containing the sound of solo instrumental parts.

Digital audio encoding algorithms and an analogue phonogram signal processing analog compander are designed for surgical intervention in the sound transmission process and cannot be used for measurement purposes, since the frequency processing used in them is not modified for the measurement procedure for evaluating harmonic distortions of a signal.

Description of prototypes

The closest solution to the same purpose in terms of features in relation to item 1 is the method of measuring the amplitude nonlinearity of the measurement object, which consists in decomposing the signal spectrum into the main and higher harmonics, estimating and comparing their intensities [3].

The closest solution to the same purpose in terms of features in relation to clause 2 is the method of measuring nonlinear distortions of an electrical signal, which consists in decomposing the spectrum of the first or second derivative of the signal into the main and higher harmonics, estimating and comparing their intensities [4].

The closest solution to the same purpose in terms of features in relation to clause 3 is a device for measuring harmonic distortion of an electric signal and its derivatives, containing an input and output terminal for connecting the measurement object, a harmonic oscillator, the output of which is connected to the input terminal, connected to the output terminal are serially connected adjustable block for equalizing signal levels, the first and second identical and simultaneously tunable differentiation blocks, each of which a separate switch, the first and second, respectively, is shunted, and the control and measuring unit, as well as the identical first and second display units, the input of the first display unit is connected to the output of the signal leveling unit, and the input of the second display unit is connected to the output of the second differentiation unit [5].

Prototype criticism

The reasons that impede the achievement of the required technical result when using the known method adopted for the prototype of claim 1, include the lack of correspondence between the results of objective measurement of the amplitude non-linearity of the measurement object and subjective assessment of its sound quality, since the properties of human hearing are not taken into account when implementing the known method .

The reasons that impede the achievement of the required technical result when using the known method adopted for the prototype of claim 2 are the incomplete correspondence of the results of an objective measurement of the amplitude nonlinearity of the measurement object to a subjective assessment of its sound quality, since it takes into account only the influence of higher-order nonlinearity products hearing perception of distortion. This does not take into account such a property of hearing as masking in the frequency domain and, in particular, masking with a tonal signal, which is the main harmonic of the distorted signal when a harmonic signal used in the measurement procedure is input to the measurement object.

The reasons that impede the achievement of the required technical result when using the known device adopted for the prototype of claim 3 are the lack of functionality of the proposed methods for measuring distortion.

The essence of the group of inventions

The problem to which the group of inventions claims 1 and 2 is directed is to increase the degree of conformity of the measurement results to the subjective perception of distortions.

The problem to which the invention of claim 3 is directed is to expand the functionality of the device.

This problem is solved by achieving in the implementation of the group of inventions claims 1 and 2 of the technical result, which consists in reducing the psychoacoustic redundancy of the distorted signal by formally matching the intensities of the higher harmonics with a quantitative measure of their frequency masking during auditory perception.

This problem is solved by achieving, in the implementation of the invention, claim 3 the technical result, which consists in introducing the possibilities of determining masked harmonics coefficients, masked and weighted harmonics coefficients, masked and double-weighted harmonics coefficients.

The specified technical result in the implementation of the group of inventions claims 1 and 2 is achieved by the fact that before assessing the intensities of the higher harmonics are reduced by an amount equal to the rise in the curve of the auditory threshold at their respective frequencies in the presence of a masking signal with the fundamental frequency.

The specified technical result in the implementation of the invention of claim 3 is achieved by the fact that the connection between the output of the second differentiation unit and the input of the control and measuring unit is broken and a signal frequency processing unit shunted by the third switch containing a bandpass filter and a comparison device is inserted between them the input of the bandpass filter and the first input of the comparison device are connected together and connected to the output of the second differentiation unit, the output of the bandpass filter is connected to the second input the comparison device, and the output of the comparison device to the input of the control and measuring unit, while the bandpass filter consists of inputs connected by a low-pass filter that is tunable in level and frequency and tuned by a high-pass filter, which are connected to different inputs of the adder with their outputs, the inputs of the low-pass and high-pass filters form the input of the band-pass filter, and the output of the adder - its output, in addition, the low-pass and high-pass filters are tuned in frequency simultaneously.

The analysis of the prior art by the applicant, including a search by patent and scientific and technical sources of information, allowed to establish that the applicant did not find analogues that are characterized by signs identical to all the essential features of the claimed group of inventions, and the definition of prototypes from the number of identified analogues as the closest in the totality of signs allowed us to determine the set of essential in relation to the technical results of the features in the claimed group set forth in the claims.

Therefore, the claimed group of inventions meets the requirement of "novelty" of the current legislation.

To verify the conformity of the claimed group of inventions to the requirements of the inventive step, the applicant conducted an additional search for known solutions in order to identify features that match the features that are distinctive from the prototypes, the results of which showed that the claimed group of inventions does not follow explicitly from the prior art, since from the prior art determined by the applicant, the influence of the essential features of the claimed group of inventions has not been identified converted si to achieve a technical result.

Therefore, the claimed group of inventions meets the requirement of "inventive step" of the current legislation.

List of drawings

Figure 1 presents the following frequency dependencies: 1 - curve of the absolute threshold of audibility; 2 - curve of the threshold of audibility in the presence of a masking signal with a frequency of 1 kHz and an intensity of 100 dB; 3 - curve of the threshold of audibility in the presence of a masking signal with a frequency of 1 kHz and an intensity of 80 dB; 4 - curve of the threshold of audibility in the presence of a masking signal with a frequency of 1 kHz and an intensity of 60 dB; 3a is a horizontal line; 3b is a curve approximating the high-frequency slope of the curve of the auditory threshold in the presence of a masking signal with a frequency of 1 kHz and an intensity of 80 dB; 5 - approximated amplitude-frequency characteristic of the high-pass filter; 6 - vertical line at a frequency of 1 kHz.

Figure 2 presents the structural diagram of a device that implements the proposed measurement methods, where 1 is a generator of harmonic oscillations; 2 - measurement object; 3 - adjustable block alignment of signal levels; 4 - the first display unit; 5 - the first block of differentiation, 6 - the first switch; 7 - the second block of differentiation; 8 - second switch; 9 - second display unit; 10 - control and measuring unit; 11 - input terminal; 12 - output terminal; 13 - block frequency signal processing; 14 is a comparison device; 15 - band-pass filter; 16 - tunable in level and frequency low-pass filter; 17 - tunable high-pass filter; 18 - adder; 19 - the third switch. In this case, the first 5 and second 7 differentiation units are identical to each other and are simultaneously tuned, the first 4 and second 9 display units are identical to each other, and the filters 16 and 17 are simultaneously tuned in frequency.

Information confirming the possibility of implementing a group of inventions

Information confirming the possibility of implementing a group of inventions with the receipt of these technical results are as follows.

The wide and successful use of the properties of frequency masking of hearing in order to reduce the amount of transmitted audio information allowed us to suggest the appropriateness of taking this phenomenon into account during the measurement procedure for estimating the magnitude of harmonic distortions of an electrical signal due to the amplitude non-linearity of the measurement object. This will increase the degree of conformity of the measurement results to the auditory perception of distortions arising during the reproduction of audio programs by the measurement object.

During the development of modern algorithms for encoding audio information, numerous and varied informational and psychoacoustic studies were carried out, the results of previous studies were attracted, which made it possible to carefully study perception issues and obtain fundamental quantitative dependencies that generalized the results of theoretical and experimental studies. It should be noted that at present, when implementing software and hardware sound technical means, the simultaneous (monoural) masking, manifested in the frequency domain of perception, is mainly taken into account from the hearing-related phenomena of masking.

To achieve the effect of repeatability of the measurement results obtained at various facilities, the simplicity of measurements and the reduction of material and technical costs for the manufacture of facilities, we will abandon the detailed modeling of the fundamental properties of hearing and turn to the use of formal harmonization of the measurement results with auditory perception of distortion by selecting the appropriate form of the frequency response, correcting the measurement results is adequate to auditory perception. We propose to improve the prototype methods by introducing, before decomposing the signal spectrum into the main and higher harmonics, the frequency processing operation introducing the indicated agreement.

We form the form of the frequency characteristics that correct the spectrum of higher harmonics, taking into account their masking, for the subsequent removal of the corrected spectrum from the spectrum of the original signal at its various intensities.

The choice of the forms of corrective characteristics is based on the curves of the threshold of hearing, borrowed from the works of E. Zwicker, R. Ehmer, L. Fielder and E. Benjamin. It is these data that are used in the work of the psychoacoustic model of the A / 52 compression algorithm of the ATSC Dolby AC-3 standard. At the same time, we note that the curves of the threshold of audibility when masking with a tonal signal are too complicated for their hardware implementation. Therefore, we turn to the form of the correcting characteristic corresponding to the curve of the threshold of audibility in the presence of a masking narrow-band noise, and assume that the noise signal is so narrow-band that it can be arbitrarily positioned at the fundamental frequency and taken as a tonal signal. This is quite acceptable, since the adoption of the premise of striving to formally agree on the measurement results with an auditory assessment of distortions means that the frequency processing operation should not be considered as modeling the properties of hearing — its task is only to “fit” the effect obtained at the output of the measuring system to a subjective quantitative least assessed as distortion of the shape of the initially harmonic signal.

Figure 1 presents the frequency dependence, reflecting the modification of the curve of the threshold of audibility in silence - the absolute threshold of audibility (APS), in the presence of a masking signal. Here, the frequency dependence of the APS (curve 1) and the family of curves of the auditory threshold (PS) in the presence of a masking signal with a frequency of 1 kHz of various intensities are presented: 100 dB, 80 dB, and 60 dB (curves 2-4, respectively). The parameter of each curve is the absolute acoustic level of the masking signal, dB, calculated relative to the sound pressure of 2 × 10 ^-5 Pa. Similar dependences are also known for other frequencies of the masking signal in the audio range of 20 Hz – 20 kHz.

Let us turn to the value of the frequency of the test harmonic signal equal to 1 kHz, which is most often used in the measurement of harmonic distortion. As a result of the presence of amplitude non-linearity of the transfer characteristic of the measurement object, distortions in the shape of its output signal occur, which corresponds to the appearance in the signal spectrum of higher harmonics with frequencies that are multiples of the fundamental frequency: second, third, fourth, etc. harmonics. The presence of one or another higher harmonic, the evenness or oddness of its number, and its intensity depend on the type of amplitude nonlinearity of the device under test.

From the point of view of the presence of psychoacoustic redundancy of the distorted signal, the main harmonic can be considered as a masking signal, and the higher-order harmonics nearby in frequency can be considered as masked signals that fall into the masking zone and to which the hearing loses susceptibility if their intensities are below the PS curve. The number of masked harmonics depends on the intensity of the fundamental. So, for example, for curve 4 in figure 1, the second and third harmonics with frequencies of 2 and 3 kHz will fall into the masking zone. This means that the intensities of these harmonics should be reduced by an amount equal to the value of the rise of the curve of the threshold of hearing with respect to the APS (Fig. 1, curve 1).

Note that in the course of subjective examinations, the optimum sound pressure value of 82 ± 2 dB was determined, the establishment and maintenance of which in the auditorium or listening room will correspond to the level of sound reproduction in the control room (room) of the film studio, recording studio, etc., and means, it will guarantee the reliability of the transmission of audio information. The optimal value of sound pressure corresponds to curve 3 in figure 1. In modern operating conditions of sound equipment, listening levels reach 100 decibels or more, which corresponds to curve 2 in figure 1.

We turn to curve 3 in FIG. 1, corresponding to the PS curve at a masking signal intensity of 80 dB. Since only higher harmonics should be processed, the fundamental should be excluded from the signal at a frequency of 1 kHz. This can be done using a high-pass filter (HPF), the approximated amplitude-frequency characteristic (AFC) of which corresponds to curve 5 in figure 1. Harmonics above the second fall into the passband of the filter, and the main harmonic will be suppressed. The presented HPF frequency response is also applicable when using other PS curves and does not need level adjustment. Only frequency tuning is required when the frequency of the test harmonic signal changes.

Next, it is necessary to influence the intensities of higher harmonics in a strictly defined quantitative ratio corresponding to the high-frequency slope of the PS curve — curve 3 above a frequency of 1 kHz. This can be achieved using a low-pass filter (low-pass filter), the frequency response of which can be approximated using a straight line (line 3a in figure 1) in the transmission zone in combination with an inclined curve (curve 36 in figure 1) in the transition zone simulating a part PS curve. The frequency zone located between the frequency response of the high-pass filter and the frequency response of the low-pass filter (hatched by the inclined lines) is inherently the transmission band of the band-pass filter, which will include those parts of the higher harmonics intensities that will be masked by the auditory system, which means they will not be heard. Then it follows from the spectrum of the original signal to subtract the spectrum of masked higher harmonics, missed by the band-pass filter, and then the main harmonic and higher harmonics with changed intensities will be present in the spectrum of the measured signal, according to one or another frequency response of the band-pass filter, which is determined by the level of the original signal.

The frequency response of the band-pass filter, formed by the parts of dependencies 5 and 3b, restricting the area shaded in Fig. 1, will be that corrective characteristic, the formal use of which during the frequency processing of the measurement results will achieve the desired result. Other forms of frequency response of the band-pass filter at other intensities of the original signal are generated in a similar manner to that described above.

For the proposed measurement methods, the initial signal subjected to the above-described frequency processing is either the output signal of the measurement object, or a differentiated signal at the output of the first differentiation unit, or a twice-differentiated signal at the output of the second differentiation unit.

Further, the measurement procedure requires an assessment and comparison of the intensities of the signal components, which can be carried out using radio measuring instruments included in the control and measuring unit. Quantitative estimates of distortion will be partial and / or total coefficients. In the implementation of the method of claim 1, these are the coefficients of masked harmonics, in the implementation of the methods of claims 2 and 3, these are the coefficients of masked and weighted harmonics and the coefficients of masked and double-weighted harmonics.

Implement the steps of the measuring procedure described above using the proposed device, the structural diagram of which is presented in figure 2. It consists of a series-connected harmonic oscillation generator 1, a measurement object 2 connected between input 11 and output 12 terminals, a tunable leveling unit 3, a first differentiation unit 5, a second differentiation unit 7, a measurement and control unit 10, and also a first switch 6, a shunting first differentiation unit 5, a second switch 8, a shunting second differentiation unit 7 and identical first 4 and second 9 indication blocks connected respectively to the output of block 3 are aligned signal levels and the output of the second block 7 differentiation. Block 3 equalization of signal levels, as well as the first 4 and second 9 display units provide a reduction in methodological measurement errors that are inevitable when conducting hardware differentiation. The presence of these units does not affect the measurement results, since they do not introduce changes in the shape of the electrical signal.

The input unit is a frequency signal processing unit 13, shunted by the third switch 19, connected between the output of the second differentiation unit 7 and the input of the control and measuring unit 10 and consisting of a comparison device 14 that finds the difference between the original distorted signal (differentiated, differentiated twice or not at all the differentiated output signal of the measurement object 2, which depends on the positions of the first 6 and second 8 switches) and the signal obtained from the source first, by processing with a band-pass filter 15, in which the intensities of higher harmonics are influenced, according to one or another PS curve, corresponding to the frequency and intensity of the masking signal, which is the main harmonic. The band-pass filter 15 is implemented by parallel switching on the low-pass filter 16 and the high-pass filter 17. Their output signals are fed to the inputs of the adder 18. Filters 16 and 17 in frequency are tuned simultaneously. Simultaneous frequency tuning of the filters 16 and 17 will be required when the frequency of the test harmonic signal generated by the harmonic oscillation generator 1 is changed. Only level 16 low-pass filter needs level adjustment. It will be required during measurements, the conditions of which provide for other levels of listening using object 2 measurements.

The source signal and the output signal of the adder 18 are fed to different inputs of the comparison device 14, the output signal of which is then subjected to a qualitative and quantitative analysis of the devices in the control and measuring unit 10.

Obtaining the source signal when implementing the proposed method of claim 1 is achieved by closing the first 6 and second 8 switches. Obtaining a similar signal for the implementation of the proposed methods of claims 2 and 3 is achieved by opening the first switch 6 or both switches 6 and 8.

The control and measuring unit 10 may contain an oscilloscope, a frequency-selective voltmeter, and / or an industrial meter of nonlinear (more precisely, harmonic) distortions, which will allow for visual observation of the waveform, as well as to isolate and evaluate the intensities of all harmonics or directly determine one or another total coefficient distortions.

A quantitative assessment of the total and / or partial coefficients additionally determined by the device is carried out in the same way as in the standardized prototype method of claim 1: for partial coefficients, the ratios of the intensities of individual harmonics to the intensity of the first harmonic are found, for the total coefficient, the ratio of the rms sum of the harmonics intensities is found higher orders either to the intensity of the first harmonic, or to the rms sum of the intensities of all harmonics.

We give to the input of the object 2 measurements test harmonic signal of the form

$$s_{\mathrm{at}x}\left(t\right)=S_m\cos \left(\omega t+{\varphi }_o\right),\text{(one)}$$

where S _m is the amplitude value; φ _about - the initial phase.

Suppose that the nonlinearity of the measurement object 2 can be described by a polynomial of the form

$$s_{\mathrm{at}sx2}\left(t\right)={\displaystyle \sum _{n=\mathrm{one}}^k{a}_n{s}_{\mathrm{at}x}\left(t\right)}.\text{(2)}$$

The output signal of the measurement object 2 is distorted, i.e. in its spectrum, in addition to the fundamental harmonic, higher order harmonics will appear.

In the General case, the expression for the output signal of the measurement object 2 can be written

$$s_{\mathrm{at}sx2}\left(t\right)=S_P+{\displaystyle \sum _{n=\mathrm{one}}^k{S}_{mn}\cos \left(n\omega t+{\varphi }_n\right)},\text{(3)}$$

where S _p is a constant component, which is not subjected to evaluation during measurements; n is the harmonic number; S _mn is the amplitude value of the nth harmonic; φ _n is the initial phase of the nth harmonic.

Expressions for partial and total harmonic coefficients measured by the prototype method of claim 1 can be written

, $$K_{Г\Sigma }=\frac{\sqrt{{\displaystyle \sum _2^k{S}_{mn}^2}}}{S_{ml}}=\sqrt{{\displaystyle \sum _2^k{K}_{Гn}^2}}.\text{ (4)}$$

$$K_{Gn}=\frac{S_{mn}}{S_{m\mathrm{one}}}$$

, $$K_{G\Sigma }=\frac{\sqrt{{\displaystyle \sum _2^k{S}_{mn}^2}}}{S_{ml}}=\sqrt{{\displaystyle \sum _2^k{\mathrm{<figure-callout\; id="2"\; label="K\; G\; n"\; filenames="00000013.png"\; state="\{\{state\}\}">K\; </figure-callout>}}_{Gn}^{}}}.\text{(four)}$$

, $$K_{МГ2}^{\text{'}}$$

, $$K_{МГ3}^{\text{'}}$$

и т.д., суммарный и частичные коэффициенты маскированных и дважды взвешенных гармоник $$K_{МГ\Sigma }^{"}$$

, $$K_{МГ2}^{"}$$

, $$K_{МГ3}^{"}$$

и т.д. Выполняться расчеты должны по формулам, аналогичным формулам (4), но амплитудные значения высших n-х гармоник должны соответствовать значениям, полученным в ходе измерения, согласно тому или иному предлагаемому способу. По своей величине эти коэффициенты окажутся меньше своих коэффициентов-прототипов, однако по своей сути полученные значения коэффициентов будут адаптированы к слуховому восприятию искажений человеком.When implementing the methods proposed in paragraphs 1 and 2, the measurement results will be the total and partial coefficients of masked harmonics K _MGΣ , K _MG2 , K _MG3 , etc., the total and partial coefficients of masked and weighted harmonics $$K_{MG\Sigma }^{\text{'}\text{'}}$$

, $$K_{MG2}^{\text{'}\text{'}}$$

, $$K_{MG3}^{\text{'}\text{'}}$$

etc., the total and partial coefficients of masked and double-weighted harmonics $$K_{MG\Sigma }^{"}$$

, $${\mathrm{<figure-callout\; id="2"\; label="K\; M\; G"\; filenames="00000013.png"\; state="\{\{state\}\}">K\; </figure-callout>}}_{MG}^2$$

, $${\mathrm{<figure-callout\; id="3"\; label="K\; M\; G"\; filenames="00000013.png"\; state="\{\{state\}\}">K\; </figure-callout>}}_{MG}^3$$

etc. Calculations should be performed according to formulas similar to formulas (4), but the amplitude values of the highest n-th harmonics should correspond to the values obtained during the measurement, according to one or another proposed method. In terms of magnitude, these coefficients will be less than their prototype coefficients, however, in essence, the obtained coefficient values will be adapted to the auditory perception of distortions by a person.

Thus, the introduction into the measuring procedure of the claimed measurement methods (paragraphs 1 and 2 f-ly) of the operation of changing the intensities of the higher harmonics in accordance with the rise of the curve of the auditory threshold will provide an increase in the degree of correlation of objective and subjective assessments of sound quality. In this case, the introduction of the frequency processing unit into the claimed device (Clause 3) will allow it to have additional functions relative to the prototype — the ability to determine distortion coefficients that reflect the effect of hearing masking of higher harmonics of the signal, which allows to expand the set of non-linearity coefficients determined with its help .

The above information indicates the fulfillment of the following conditions when using the claimed group of inventions:

- the method (options) and device embodying the claimed group of inventions in their implementation are intended for use in instrumentation for detecting and evaluating harmonic distortion of a signal introduced by sound equipment, in particular sound reinforcement equipment;

- for the claimed group of inventions, as described in the claims, the possibility of their implementation using the methods described above or known before the priority date of the funds is confirmed;

- the method (options) and device embodying the claimed group of inventions in their implementation, are able to achieve the specified technical result.

Therefore, the claimed group of inventions meets the requirement of "industrial applicability" under applicable law.

Literature

1. Kovalgin Yu.A., Vologdin E.I. Digital coding of audio signals. - St. Petersburg: CROWN-print, 2004 .-- 240 p. (p. 129-210).

2. Gendry K. Noise Reduction Systems. - M.: Sound producer, 2004, No. 6, p. 49-53.

3. GOST 23849-87. RADIO ELECTRONIC APPLIANCES HOUSEHOLD. Methods for measuring the electrical parameters of sound frequency signal amplifiers, Section 4.6.1 - prototype of Claim 1.

4. Copyright certificate 1120253 A, IPC G01R 23/20. A method for measuring nonlinear distortion of an electric signal and a device for its implementation / Zhuravlev V.M., Tikhonova L.S .; applicant and patentee of the Leningrad Institute of Film Engineers. Published: 10.23.1984, Bulletin No. 39 - prototype of Claim 2

5. Patent for the invention 2456624 (RU 2456624 C1) of the Russian Federation, IPC G01R 23/20 (2006.01). A device for measuring harmonic distortion of an electrical signal and its derivatives / L. Tikhonov; Applicant and patent holder St. Petersburg State University of Cinema and Television. - No.2010145565 / 28, 11/09/2010. Published: July 20, 2012, Bulletin No. 20 - prototype of Clause 3 of the Law.

Claims (3)

1. A method for measuring harmonic distortion of an electrical signal, which consists in decomposing the signal spectrum into the main and higher harmonics, evaluating and comparing their intensities, characterized in that before their assessment, the intensities of the higher harmonics are reduced by an amount equal to the rise in the curve of the auditory threshold at their respective frequencies in the presence of a masking signal with a fundamental frequency. 2. A method for measuring harmonic distortion of an electric signal, which consists in decomposing the spectrum of the first or second derivative of the signal into the main and higher harmonics, evaluating and comparing their intensities, characterized in that before their assessment, the intensities of the higher harmonics are reduced by an amount equal to the value of the rise in the curve of the threshold of hearing at their respective frequencies in the presence of a masking signal with a fundamental frequency. 3. A device for measuring harmonic distortion of an electrical signal, containing input and output terminals for connecting the measurement object, a harmonic oscillator, the output of which is connected to the input terminal, an adjustable level signal leveling unit connected in series, the first and second identical and simultaneously tunable, connected to the output terminal differentiation units, each of which is shunted by a separate switch, the first and second, respectively, and a control and measuring unit, and the first and second display units are identical, the input of the first display unit is connected to the output of the signal leveling unit, and the input of the second display unit is connected to the output of the second differentiation unit, characterized in that the connection between the output of the second differentiation unit and the input of the control and measuring unit is broken and between them a frequency signal processing unit is introduced, shunted by the third switch, comprising a band-pass filter and a comparison device, wherein the input of the band-pass filter and the first input of the comparison device is connected together and connected to the output of the second differentiation unit, the output of the band-pass filter is connected to the second input of the comparison device, and the output of the comparison device is connected to the input of the control and measuring unit, while the band-pass filter consists of the filter and level-frequency tunable inputs low-pass and frequency-tunable high-pass filter, which with their outputs are connected to different inputs of the adder, and the inputs of the low-pass and high-pass filters form the input of the bandpass filter, and the output of the adder is its output, moreover, the low and high frequency filters are tuned in frequency simultaneously.

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