RU2013030C1 - Device for testing of irregularity of frequency characteristic of sensitivity of microphone - Google Patents

Abstract

FIELD: radio engineering. SUBSTANCE: device includes radiator 1, fixed frequency generator 2, reference generator 3, controlled microphone 4, voltage converter 5, analog-to-digital converters 6, 7, delay element 8, visualization unit 9, control unit 10, controlled attenuator 11, two memory registers 12, 13, two comparators 14, 15, 1 AND gate 16. EFFECT: improved accuracy and reliability of testing. 7 dwg

Description

 The invention relates to instrumentation and can be used to control microphones or microphone paths in sound reproduction equipment.

 A device is known that provides control of the frequency response of the microphone at points on a sinusoidal signal and contains a signal generator, emitter, measuring amplifier, the input of which is connected to a controlled microphone, voltmeter (GOST 16123-88 "Microphones", p. 17, 18).

 The disadvantage of this device is that it does not have a means of comparing the controlled sensitivity values in the control process.

 Closest to the proposed device is [1].

 The known device comprises a fixed frequency generator, a reference generator, the combined outputs of which are connected to a radiator, two digital-to-analog converters (DACs), a 2I element and a visualization unit connected in series, a delay element and a control unit whose outputs are connected to the inputs of a fixed frequency generator, a reference generator, delay element and the control input of the first DAC.

 The disadvantage of this device is the low accuracy of the measurements.

 The aim of the invention is to increase accuracy.

 To this end, into a device containing a radiator, a fixed-frequency generator, the output of which is combined with the output of the reference generator and connected to the radiator, a controlled microphone connected via a voltage converter to the input of the first analog-to-digital (A-C) converter, the second A-C converter , a delay element, a visualization unit and a control unit having connections with the input of a fixed-frequency generator, with a control input of the first A-C converter, with a visualization unit and with the input of a reference generator, unlike e from the prototype, a controlled attenuator, first and second memory registers, first and second comparators, element 2I are introduced, while the input of the first A-C converter through the attenuator is connected to the input of the second A-C converter, and the control input of the first A-C the converter is combined with the control input of the second A-C converter, the output of the A-C converter is simultaneously connected to the corresponding first inputs of the first comparator and to the information inputs of the first memory register, and the outputs of the second A-C converter are simultaneously under are connected to the corresponding first inputs of the second comparator and to the information inputs of the second memory register, the outputs of the first memory register are connected to the corresponding second inputs of the second comparator, and the outputs of the second memory register are connected to the corresponding second inputs of the first comparator, the control inputs of the memory registers are combined and connected to the element output delays, the input of which is connected to the input of the reference generator, the outputs of the comparators through element 2and connected to the input of the visualization unit, the control unit s an communication with the control inputs of the attenuator.

 The connection of the control unit with the control inputs of the attenuator is a well-known technical technique, therefore this feature is distinctive only in relation to the prototype.

 The introduction of the blocks indicated in the distinctive part of the formula, as well as the relations due to this introduction, will achieve the goal, and therefore they are significant.

 Devices with signs distinguishing the proposed from the known, not found.

 In FIG. 1 presents a structural diagram of the proposed device; in FIG. 2 is a timing diagram of the operation of the device; in FIG. 3 - frequency response of the controlled microphone; in FIG. 4 and 5 - functional diagram of the control unit; in FIG. 6 is a functional diagram of a controlled attenuator; in FIG. 7 is a functional diagram of the ADC.

The device comprises an emitter 1, a generator 2 of fixed frequencies, the output of which is combined with the output of the reference oscillator 3 and connected to the emitter 1, a controlled microphone 4 connected through a voltage converter 5 to the input of the first analog-to-digital A-C converter 6, the second A-C converter 7, delay element 8, visualization unit 9, outputs 9 $\genfrac{}{}{0ex}{}{\text{1}}{\text{1}}$ ₀ . . . 9 $\genfrac{}{}{0ex}{}{\text{<figure-callout id="1" label="n" filenames="00000002.png,00000003.png" state="{{state}}">n</figure-callout>}}{\text{1}}$ ₀ which are in communication with a control unit 10, which is in communication with a control unit 10, which has a connection 10 $\genfrac{}{}{0ex}{}{\text{1}}{\text{2}}$ . . . 10 $\genfrac{}{}{0ex}{}{\text{<figure-callout id="2" label="m" filenames="00000002.png,00000003.png" state="{{state}}">m</figure-callout>}}{\text{2}}$ with the input of the generator 2 of fixed frequencies, 10 ₆ with the control input of the A-D converter 6, 10 ₃ - with the input of the reference generator 3, with the clock input of block 9 (communication "1" in Fig. 1), a controlled attenuator 11, the first and the second memory registers 12, 13, the first and second comparators 14, 15, element 2I, 16, while the input of the A-C converter 6 through the attenuator 11 is connected to the input of the A-C converter 7, and the control input of the A-C converter 6 is combined with the control input of the A-D converter 7, the outputs of the A-D converter 6 are simultaneously connected to the corresponding first (A) the inputs of the comparator 14 and the information inputs of the register 12, and the outputs of the A-D converter 7 are simultaneously connected to the corresponding first (A) inputs of the comparator 15 and the information inputs of the register 13, the outputs of the register 12 are connected to the corresponding second (B) inputs of the comparator 15, and the outputs of the register 13 are connected to the corresponding second (B) inputs of the comparator 14, the control inputs of the registers 12, 13 are combined and connected to the output of the delay element 8, the input of which is connected to the input of the reference generator 3, the outputs A> B of the comparators 14, 15 through the ele ment 2I 16 are connected to the input of the visualization unit 9, the control unit 10 has a connection 10 $\genfrac{}{}{0ex}{}{\text{1}}{\text{1}}$ ₁ . . . 10 $\genfrac{}{}{0ex}{}{\text{to}}{\text{1}}$ ₁ with the control inputs of the attenuator 11, the emitter 1 and the controlled microphone 4 are placed in a muffled sound chamber 17.

 Consider the algorithm of the device, which is as follows.

When measuring sensitivity at several points, in particular microphones (at several test frequencies relative to the reference), the following algorithm of actions is usually used (Fig. 3):
measuring sensitivity at a reference frequency (f ₀ ) in dB (0 dB);
multiplying the obtained value (0) by the coefficient Δ α _i , thereby calculating the upper limit;
divide the value (0) by the coefficient Δ β _i , obtaining the lower boundary;
measuring sensitivity at the corresponding i-th test frequency;
determined by comparison, whether the sensitivity value at the test frequency is within the established boundaries (inside).

In the proposed device, the operation of multiplying the sensitivity value at the reference frequency by a coefficient Δ α _i replacing the operation by dividing the sensitivity at the corresponding i-th test frequency by the same coefficient (Δ α _i ).

 When performing the operations of division and multiplication in an analogous manner, the operations of division are simpler than the operations of multiplication.

 Indeed, for multiplication, at least an amplification stage is required, i.e. a set of active and passive elements, and the higher the accuracy of the calculation, the more elements (transistors, resistors, etc.). The fission operation with high accuracy can be implemented on two resistors.

In the proposed device, the calculation algorithm is as follows (Fig. 3):
sensitivity is measured at the reference frequency (0 dB) and taken as its upper limit (B);
divide the value (B) by β _i , obtaining the lower boundary of B;
sensitivity is measured at the i-th test frequency, obtaining the first compared value (B _i );
dividing the value of B _i by the coefficient Δ α _i , obtaining the second compared value (N _i );
comparing the values, if B _i > H and H _i <B, then this means that the relationship between the sensitivity at the reference frequency and the sensitivity at the i-th test frequency does not go beyond the boundaries.

 The fixed frequency generator 2, as well as the reference generator 3, can be made in the form of separate sinusoidal generators with the Wien-Robinson bridge (Semiconductor circuitry, W. Imice, K. Schnek. - M: Mir, 1982, p. 304, Fig. 18 , 22), the outputs of which through the multiplexer are connected to the output of the generator, while the address inputs of the multiplexer are the input of the generators 2.3.

 The voltage converter 5 can be made in the form of a precision two half-period rectifier with an input amplifier that converts the input alternating voltage into proportional - constant (Semiconductor circuitry. U. Titze, K. Schenck, p. 471, Fig. 25.10).

 The ADCs 6 and 7 can be a counter-type ADC of a sequential type, performed in a known manner (Fig. 7).

The delay element 8 can be performed in a known manner on digital microcircuits, for example, on the 155 series, which implements a delay of the leading edge of the input pulse voltage. Imaging unit 9 can be of a decoder and a block "D" flip-flops by the number of fixed-frequency oscillator 2, to which are connected outputs of the first LEDs and the second outputs are connected to connections 9 ₁₀ ^1. . . 9 ₁₀ ⁿ with block 10. The clock inputs of the triggers are connected and connected to the output "T" of block 10, and the "D" inputs are combined and are the input of block 9. "P" inputs of the triggers are connected to the corresponding outputs of the decoder, the inputs of which are connected by 109 ¹ . . . 109 ^m with block 10.

The corresponding trigger of block 9 is selected by means of a code on outputs 109 ¹ . . . 109 for recording in it the result of the control by the imrulse from the output “T” of block 10.

 The control unit 10 is a program-time block realizing the organization of the time diagram shown in FIG. 2, and can be performed, for example, on 155-series microcircuits.

 The controlled attenuator 11 (see Fig. 6) can be performed on resistive dividers connected according to the potentiometer circuit, the outputs of which through the multiplexer (single or multi-stage) are connected to the output of the attenuator, and the inputs of the dividers are combined and are the input of the attenuator, the address inputs of the multiplexer are attenuator control inputs.

Comparators 14, 15 can be performed on chips 134SP1, and the outputs A> B of the chips are the outputs of the comparators, where A is the number at the first inputs of the comparators;
B - numbers on the second inputs of the comparators.

 Consider the operation of individual units of the device.

 An analog-to-digital converter (Fig. 7) works as follows.

By the pulse at the control input 10 ₆ (Fig. 7), the trigger T is set to unity, and the counter CT2 is reset. As a result of this, a voltage equal to zero is set at the output of the DAC digital-to-analog converter, and pulses from the generator through element 2I begin to arrive at the counting input CT2. The number at the output of CT2 increases, respectively, the voltage at the output of the DAS reaches the value of the voltage at the input, the comparator is triggered. The trigger T is set to zero, prohibiting the further passage of pulses from the generator G to the counter CT2. This completes the conversion cycle, while at the output of the counter a number is formed proportional to the value of the input voltage.

 The control unit 10 (Fig. 4 and 5) operates as follows.

According to the impulse from the one-shot G 1 "Record" controlled by the "Start" button, the trigger T "1" is set to "1". As a result, along the front of the first clock pulse from the generator G 1 from the output T "1" is recorded in the first bit of the shift register PG. On the same front, trigger “1” is set to “0” (a failure in record “1” in the first bit of register PG does not occur due to the delay in switching trigger T1 equal to usually several tens of nanoseconds). The recorded unit is shifted in the register RG with the help of clock pulses from the generator G and arrives at the outputs 10 ₆ and "T" of block 10 through OR circuits, and also turns on and off the triggers T. At the outputs of the triggers T, a certain time sequence of pulses is formed. The pulses from the outputs of the odd triggers T through the OR circuit "1" go to the output 10 _{3 of} block 10, and then through the OR circuit "2" to the counting inputs of the counters, and the pulses from the outputs of the even triggers through the OR circuit "3" and then through the OR circuit "2" also to the counting inputs of binary counters. The outputs of the counter "1" are outputs 10 ₂ ¹ . . . 10 ₂ ^m and 10 ₉ ¹ . . . 10 ₉ ^{m of} block 10, counter "2" - outputs 10 ₁₁ ¹ . . . 10 ₁₁ ^to block 10. In general, a temporary pulse train, shown in FIG. 2. When the device operates in the "Before the first marriage" mode (the "Before the first marriage" switch is closed), then in the case of the first marriage on one of the inputs 9 ₁₀ ¹ . . . 9 ₁₀ ⁿ , the corresponding voltage level appears, which, through the OR inhibit circuit and element 2I, blocks the arrival of clock pulses from the generator G to the clock input of the PG register, and also triggers the one-shot G1 Reset, with which the PG register and all block triggers are reset 10. Functional diagram of block 10 in FIG. 4 and 5 (the number of addresses in the diagram) is made for the device conducting control at seven test frequencies relative to the reference frequency.

 The device of FIG. 1 works as follows.

The control unit 10 forms
- start signal (output 10 ₃ ) of the reference generator;
- codes for selecting test frequencies of generator 2 (outputs 10 ₂ ¹ ... 10 ₂ ^m );
- codes for the selection of the division factors Δ α _i and Δ β _i 10 ₁₁ . . . 10 ₁₁ ^k ;
- signal for reading control results (output 10 ₆ );
- codes for selecting an indication element for implementing the operation mode of the device prior to the first marriage (outputs 10 ₉ ¹ ... 10 ₉ ^m );
- signal read result (output "T").

At the initial time t ₀ (Fig. 2), a trigger signal generated at the output 10 of the control unit 10 starts the generator 3 and is supplied to the input of the delay line 8. As a result, the voltage of the reference frequency f ₀ from the output of the generator 3 is supplied to the emitter 1. Simultaneously with exit 10 ₁₁ . . . 10, ₁₁ ^{to the} control unit 10 to the input of the attenuator 11 enters the code corresponding to the value of Δ β _i at frequency f _i and the attenuator via resistive divider is set to Δ β _i - tolerance for deviation of sensitivity from the nominal value on the frequency t _i downwards.

The sound pressure generated by the emitter 1 in the muffled chamber 17, is perceived by a controlled microphone 4, which converts it into a voltage proportional to its sensitivity. This voltage is converted by the Converter 5 into a constant voltage, which is fed to the input of the ADC 6 directly. The same voltage from the converter 5 is attenuated (divided) by Δ β _i times on the attenuator 11 and is fed to the ADC 7. By the signal of reading the control result from the control unit 11 (output 10 ₆ ) (Fig. 2e), corresponding to the time t _i , begins the calculation of the voltage values at the inputs of the ADC 6 and 7 (Fig. 2). By the time t ₂ and t ₃ (Fig. 2E), the calculation of the input value ends. The time is defined as the sum of the response time of the emitter 1 + the propagation time of the wave from the emitter 1 to the controlled microphone 4 + the conversion time of the transducer 5, with the total time t ₁ <time interval t ₀ - t ₁ . The values of t ₂ and t ₃ correspond to the conversion time of the input signals to the ADCs 6 and 7. According to the start signal delayed by the delay element 8 by the time t ₄ supplied to the control inputs of the registers 12 and 13, the information from the outputs of the ADC 6 and 7 is written into the registers 12 and 13, and then goes to the inputs of the comparators 15, 14 (inputs A). At time t _5, at the end of the time trigger signal, the sensitivity measurement at the frequency f _{0 of} microphone 4 ends. The values obtained when measuring the sensitivity of the microphone 4 at the reference frequency are used hereinafter as the settings for measuring sensitivity at a frequency f ₁ .

The next cycle is the measurement of sensitivity at a frequency of t ₁ (Fig. 3). At the input of the generator 2 of fixed frequencies, a code corresponding to the frequency is supplied, for example, t ₁ from the control unit 10. As a result, a voltage with a frequency f _{1 a} voltage with a frequency f ₁ is supplied to the emitter 1, at the same time in the attenuator 11 in accordance with the code of the control unit 10, the coefficient Δ α _i (Δ α ₁ ) is set - the tolerance for deviation of sensitivity from the nominal value in the direction of increase by frequency f _i (f ₁ ), which corresponds to the upper tolerance limit. Indeed, if the sensitivity value at the frequency f ₁ , being weakened by the tolerance value, will be less than the underexposed sensitivity value of the microphone 4 at the reference frequency, this means that the sensitivity at the frequency f _{1 is} not higher than the set limit. Similarly, on command from the ADC control unit 10, 6 and 7, the voltage values are started from the converter 5 and attenuated 11 times Δ α _i (Δ α ₁ ) from the attenuator 11 (time t _{7 of} Fig. 2c, d), which is proportional to the sensitivity of the microphone 4 at a frequency f ₁ . At time t ₇ , t ₈ the voltage conversion to the ADC 6 and 7 ends and the information from the ADC outputs goes to the inputs of the comparators 14, 15 (inputs B). Moreover, if the sensitivity of the microphone at a frequency f ₁ is within the tolerance (Fig. 3 frequency f ₁ ), then the outputs of the comparators 14, 15 A> B will have a high voltage level, which through element 2I 16 will go to the input of the visualization unit . If the difference of the compared values does not exceed the maximum permissible, then a display signal is supplied to block 9, which, upon command from the control block 10, will record the control result (in this case, "Good" f ₁ ). Next, the device proceeds to measuring the sensitivity of the microphone 4 at a frequency f ₂ . To do this, again measure the sensitivity of the microphone at the reference frequency f ₀ (time t ₁₂ ) for subsequent comparison with sensitivity at a frequency f ₂ . The sensitivity measurement at the reference frequency is similar to that described above, while the attenuator division ratio is chosen equal to Δ β ₂ (Fig. 3). At time t _{14, the} second sensitivity measurement at a frequency f ₀ ends and the sensitivity measurement of the microphone 4 at a frequency f ₂ (time t ₁₅ ) begins, similar to the measurement at a frequency f ₁ . For this, the input from the generator 2 is supplied with a code from the control unit 10 corresponding to the frequency f ₂ . Simultaneously with the control unit 10, the attenuator division factor is set to the value Δ α ₂ (Fig. 3). Let the sensitivity of the microphone 4 at a frequency f _{2 be} higher than the permissible value, then at the output of the comparator 14 A> B is a high voltage level, and at the output of the comparator 15 A> B is a low voltage level. At the output of element 2I 16 there will also be a low voltage level (Fig. 2l) and a signal is sent to the visualization unit 9 to display a sensitivity value mismatch. At the same time, the control unit 10, upon a signal from block 9, can stop the control device if it operates in the "Before the 1st defect" mode.

Sensitivity control at subsequent frequencies (f ₃ ... F _n ) is similar to that described above. Moreover, when measuring the sensitivity of the microphone 4 at the reference frequency, the division coefficients of the attenuator 11 are set equal to Δ β ₃ . . . Δ β _n, respectively, and when measuring sensitivity at frequencies f ₃ . . . f _n -Δ α ₃ . . . Δ α _n, respectively.

Thus, the present invention allows to simplify the known device by excluding from it functions such as:
- definition of a private sign;
- shift the number to the left;
- subtraction;
- storage of the intermediate result of subtractions;
- calculation and analysis of the number of shifts, as well as several times to reduce the number of actions required to carry out control.

To implement the control process, the proposed device must perform the following steps:
a) apply a reference frequency signal to the emitter;
b) simultaneously convert the direct and divided values of the sensitivity of the microphone at the reference frequency into codes;
c) remember the values calculated according to item b for using them as settings;
d) apply a signal of the first test frequency to the emitter;
e) simultaneously convert the direct and divided values of the microphone sensitivity at the first test frequency into codes;
e) remember the values obtained by p. d for subsequent comparison with settings;
g) compare the results of the calculations with each other, as described in the application;
h) record the result of the control (go to step a).

 So. To implement monitoring the sensitivity of the microphone at eight frequencies (one of which is the reference), the proposed device must perform N actions.

N = XY = 7 x 8 = 56, where X is the number of test frequencies;
Y is the number of actions in the proposed device when monitoring the sensitivity of the microphone at one test frequency ("at two points"). Thus, the number of actions in the proposed device is more than four times less than in the known.

Claims (1)

 DEVICE FOR MONITORING THE FREQUENCY CHARACTERISTICS OF THE MICROPHONE SENSITIVITY, containing a fixed frequency generator and a reference generator, the combined outputs of which are connected to the emitter, the first and second analog-to-digital converters, the 2I element and the visualization unit connected in series, the delay element and the control unit whose outputs are connected to the inputs of the fixed frequency generator, the reference generator, the delay element and the control input of the first analog-to-digital converter, I distinguish in that, in order to increase accuracy, the first and second comparators, the first and second memory registers, the controlled attenuator and the voltage converter are configured to connect to a controlled microphone, the output of the voltage converter being connected to the inputs of the first analog-to-digital converter and a controlled attenuator, the output of which is connected to the input of the second analog-to-digital converter, the outputs of which and the outputs of the first analog-to-digital converter are connected to information the inputs of the second and first memory registers, respectively, and the first inputs of the second and first comparators, respectively, the outputs of which are connected to the inputs of element 2I, while the second inputs of the first and second comparators are connected to the outputs of the second and first memory registers, respectively, to the control inputs of which the output of the element delays, and the outputs of the control unit are also connected to the control input of the second analog-to-digital converter, the control inputs of the controlled attenuator and the inputs of the block Visualization which outputs are connected to inputs of the control unit.

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