SU1598219A1 - Device for checking acoustic pressure of speakers - Google Patents

Abstract

The invention relates to the field of instrumentation and can be used to control the parameters of loudspeakers. The aim of the invention is to increase the reliability of the control and simplify the device. The electrical test and test signals are amplified to a reference level and the difference is determined, the difference found is attenuated and subtracted from the test one. The signal of the second difference and the attenuated signal of the first difference are transformed into a constant voltage. From the magnitude of the sum of these stresses, a conclusion is made on the sound pressure value. 2 Il.

Description

The invention relates to instrumentation and can be used to control the parameters of loudspeakers.

The aim of the invention is to increase the reliability of control by reducing the influence of acoustic noise and simplifying the device.

FIG. 1 shows a block diagram of the device; in fig. 2 - timing charts of signals, explaining the operation of the device.

The device contains a test signal generator 1, the first output of which is connected to the test loudspeaker 3 installed in the acoustic box 4, which also has a microphone 5. connected to the microphone amplifier 6, through the power amplifier 2. The second output of the generator 1 is connected through the first normalizer 7 to a non-inverting the input of the differential amplifier 8 ,.

The first and second inputs of generator 1 are connected to the first and second control outputs of the unit, 9 controls, respectively, and the control inputs of generator 1 are connected to the outputs of control unit 9. The output of the microphone amplifier 6 is connected to the first input of the adder 10 directly and through the second normalizer 11 to the inverting input of the differential amplifier 8. The second inputs of the normalizers 7 and 11 are combined and connected to the output of the constant-voltage reference source 12. The output of the differential amplifier 8 through a controlled voltage divider 13 is connected to the second input of the adder 10 directly and through successively combined rms detector 14 and the divider 15 into two - to the first input of the adder 1b, to the second input of which is connected to the second input 17

with

00

go

JA

with

Ator 10. The second output of the normalizer 1 1 is connected to the control input of the divider 13. The output of the adder 1b is connected to the input of the screening unit 18, the installation and control inputs of which are connected to the third and fourth control outputs of the control unit 9, respectively.

The device. (Fig. 1 and 2) works as follows.

 The control block 9 is started (time t,), while a code corresponding to a certain frequency 15 (for example, 63 Hz) is set at its code outputs, the pulse shaping unit 18 is reset to zero from the third control output of block 9 The control output of block 9 is the voltage of the reference 20 quartz frequency (for example, 1 MHz) and the voltage of 63 Hz is removed from the first output of the test signal generator 1 (for example, triangular in shape, Fig. 2a). This 25 voltage is amplified by the power amplifier 2 and fed to the speaker under test 3. The loudspeaker reproduces the signal applied to it. The pressure sound waves generated by the loudspeaker 3 repeat the electrical signal applied to it. Since the sound insulation coefficient of the box 4 has a certain finite value, there is an acoustic disturbance in the box k, the nature of the occurrence, the level and frequency spectrum of which is random in time. This interference to the loudspeaker of the movable system 3 distorts the pressure waveform created by it, and changes the sound pressure value (Fig. 26). At time tjy, the sound waves from the loudspeaker 3 reach the microphone 5 dZ

and is converted by it into an electric signal under study (Fig. 2c), which is amplified by a microphone amplifier 6. At the output of amplifier 6, a voltage appears

35

50

and and asinwt + and

BY

where A is the signal amplitude;

U) - frequency (63 Hz); interference voltage.

Simultaneously (i.e., through time

-AID

) at the second control output

JO1 -U

control unit 9, a control potential appears at which the voltage of 63 Hz is removed from the second output of generator 1 (Fig. 2d) and Br 3 inut.

 The signal under study from the output of the phono amplifier 6 is fed to the second normalizer 11, where it is increased by K times to the value of the reference voltage, and the output U, U x X K KCHA1pAL is obtained at the output of the normalizer-f pa; + and "(, m simultaneously, the signal from the second output of generator 1 (test signal) is fed to the output of the first normalizer 7, where it is amplified K times also to the level of the reference voltage, and the voltage is removed from its output (fig.2d)

and.

K X and „KBsincot.

one

0 5 o

DZ

five

50

In this case, the effective values of the signals at the output of the normalizers 7 and P are equal, i.e. UT U, U, is the reference voltage from the source 12 of the reference voltage.

The amplified electrical test unit from unit 7 and the test unit C of unit 11 are fed to a differential amplifier 8, from which the difference signal U g UT -and and -k and no 4- (KBsincJt-As inutK) is taken. The difference signal from amplifier 8 is attenuated. controlled by divider 13 voltage K times. This coefficient is set by the control voltage from the second output of the normalizer 11 and is equal to its gain, while the value of the attenuated signal will be equal to U ,, -and to - "

+ (Esinwc - Asinw u) 2 (-, Bsinwt - Asinwt). The attenuated signal from the divider 13 and the investigated signal from the amplifier 6 arrive at the adder 10, where the interference is compensated, and at the output of the adder 10 the signal corresponds in form to the test signal, while the effective value is equal to the actual value of the signal under study.

Next, the output voltage of the sum-, torus 10 p | is formed by the detector 17 at a constant voltage

and

 17

to to

-X and

S

where and d is the voltage proportional to bsini.

five

The output voltage from the splitter 13 voltage is formed by the detector 14 voltage, the magnitude

Ul4 2 (|, U5- and)

where and is the voltage, Asinojt,

and is divided, invert, 15 in half. As a result, living on his way out

- gfppe - a)

15

2

and at the output of the adder 16 voltage 20

GB Uc, -f. but.

Those. the value of U, j exactly reflects the value of Asincot in the signal U under study from the output of the microphone amplifier 6,

At time t, voltage, and. read by the pulse screening unit 18 from the fourth control input of the control unit 9. At time t, the signals from the output of generator 1 are removed. At this point, the first cycle of the sound pressure control of the loudspeaker 3 ends and, at the outputs of block 9, the code value is increased by one. After some time, a voltage with a different frequency (e.g., 80 Hz) appears at the first output of generator 1, and the process repeats as described. In this case, the value read by block 18 on the second cycle b (.), Divided by N, is added to the previous value Uj, (1), read on the first cycle, divided by N, where N is the number of frequencies that will be fed to loudspeaker 3 in the process of testing it. After N cycles, control block 9 returns to its original state, waiting for a new launch. The loudspeaker monitoring process ends, and in the screening unit 18, the recorded value represents the average sound pressure of the loudspeaker 3 at fixed frequencies.

6

five

0

five

0

five

0

five

0

five

Thus, the device makes it possible to increase the reliability and accuracy of monitoring the sound pressure of the loudspeakers for estimates of reducing the effect of acoustic interference on it, and to reduce the cost of the device by using a simpler sound-dampening chamber design.

Claims (1)

Invention Formula A device for monitoring the sound pressure of a loudspeaker, comprising a test signal generator, a power amplifier and a speaker under test, as well as a microphone connected to a microphone amplifier, a differential amplifier and a muffled camera in which a speaker and microphone are placed, in order to increase control accuracy by reducing the influence of acoustic noise and simplifying the device; a control unit, the first normalizer, and flaxo connected first adder, first rms detector, second adder and sorting unit, as well as series-connected reference voltage source, second normalizer, controlled voltage divider, second rms detector and divider by two, with the first input of the first normalizer connected to the second output the test signal generator, the second input is with the output of the reference HAR source, and the output is with the non-inverting input of a differential amplifier, the inverting input of which is Inen with the second output of the second normalizer, and the output with the second input of a controlled voltage divider, the microphone code amplifier is connected to the second input of the second normalizer and the first input of the first adder, the second input of which is connected to the output of the controlled voltage divider, the output of the divider two are connected to the second input of the second adder, and the control outputs of the control unit are connected to the control inputs of the test signal generator and the screening unit.