SU1651320A1 - Electropneumatic sound generator - Google Patents

Abstract

This invention relates to technical acoustics and can be used to test structures for acoustic fatigue strength and function. The purpose of the invention is to increase efficiency. When DC voltage is applied to the input of the electromagnetic system, the AC voltage through the limiter 7 I level 19 to the input of the excitation winding 7 and the compressed gas to the prechamber 1, the compressed gas flow is modulated by the moving valve 4, which results in the emission of sound waves. A cylindrical waveguide 9, whose length I is chosen from the condition, 35 n C (M / K) 1/2, where C is the speed of sound in air; M is the reduced mass of the movable valve and the exciter; K - stiffness of the suspension system, leads to an increase in the active radiation resistance in the entire frequency range, i.e. increases the efficiency of the electropneumatic sound generator. In this case, the displacement mechanism with the actuator 11 and the control system 12-19 provide for the modulation of the compressed gas flow in the optimal mode and the compensation of the Bernoulli forces. 1 il. (L C Os Joo Yu o

Description

This invention relates to technical acoustics and can be used to test structures for acoustic fatigue strength and function.

The purpose of the invention is to increase efficiency.

The drawing shows the scheme of the proposed sound generator

The electropneumatic sound generator contains prechamber 1, one of the side walls of which is a fixed valve 2 with a system of rectangular slotted channels, the distance between which along the axis is greater than their height. Inside the fixed valve 2 on the suspension system 3, there is a movable valve 4 with the same system of rectangular slotted channels. The movable valve 4 is rigidly connected to the exciter 5 exciter located in the air gap of the electromagnetic system 6. The excitation winding 7 is mounted coaxially with the exciter 5 exciter. The channels of the movable valve are connected to the pre-split chamber 8, the outlet of which is connected to the cylindrical waveguide 9. The outlet of the latter is connected to the mouth of the horn 10. The suspension system 3 is connected to the displacement mechanism 11 mounted on the housing of the electromagnetic system 6. The drive 11 bias electrically connected to the output of the amplifier 12 DC power, the input of which is connected to the comparator 13. One of the inputs of the comparator 13 is connected to the selector 14 of the variable component of the electric signal with variable transfer coefficient, and the other with a constant selector 15, the inputs of the selectors 14 and 15 are connected to a displacement sensor 16 fixed relative to the movable valve 4. One of the inputs of the comparator 17 is connected to the output of the constant selector 15, and the other with a reference signal extractor 18. The output of comparator 17 is connected to the exciter signal level limiter 19.

Electropneumatic sound generator works as follows.

The compressed gas enters the prechamber 1. When DC voltage is applied to the input of the electromagnetic system and AC voltage through the level limiter 19 to the input of the excitation winding 7, an electrodynamic force arises in the exciter 5, and the movable valve 4 comes in a reciprocating motion, modulating the gas flow flowing through the channels in the fixed 2 and movable 4 valves into the pre-barrier chamber 8,

which leads to the appearance of pressure pulses in it, which propagate as sound pressure waves through waveguide 9 and horn 10 into the environment of the generator.

To increase the efficiency of transmission of sound energy from the generator to the environment, the matching link of the generator is made in the form of successively connected cylindrical waveguide 9 and horn 10. At the same time, there is a decrease in reactance and an increase in the active resistance of radiation over the entire operating frequency range of the generator.

5 if the length of the shshovoda is chosen from the ratio of I VK / M

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0.175.

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An electrical signal proportional to the movement of a movable valve 4.

0 is supplied from the displacement sensor 16 to the selectors 14 and 15, from which direct current signals proportional to the variable and constant displacement components are transmitted to the comparator 13. In the comparator 13, a comparison of these two signals is made and, when they are different, a direct current signal of a certain sign is sent to the power amplifier 12, the amplified signal is fed to the input of the drive mechanism 11

0, which, through the suspension system 3, produces a displacement of the movable valve 4 towards the opening of the channels until the signals from the selectors 14 and 15 are matched. In addition,

5, the signal from the output of the DC selector 15 is supplied to the comparator 17, where it is compared in magnitude with the signal from the reference signal extracting unit 18. The voltage value of the reference

0 signal corresponds to the displacement of the movable valve 4 relative to the fixed 2 at half the height of the channels. When the signal exceeds a constant component, the displacement over the value

5 of the reference signal from the comparator 17 provides a signal to the exciter signal level limiter 19, where the excitation signal level is reduced to such an extent that the offset

0 of the movable valve 4 (the constant component of the movement) was equal to half the channel height. In addition, by changing the coefficient of transmission of the variable selector 14, the law

5 distribution of maxima (minima) of sound pressure with random excitation.

When the level of the alternating voltage entering the input of the excitation system changes, the movable valve is shifted by a displacement mechanism in one direction or another, depending on the sign of the difference in the magnitude of the signals of the constant selectors and the variable components of the displacement. When the rolling valve 5 is deflected under the influence of Bernoulli forces (the change in pressure of the compressed gas in the prechamber), the displacement mechanism displaces the valve in the opposite direction until the signals from the constant and variable components are compared in magnitude 10. The oscillations of the movable valve in all modes of operation of the generator occur near the neutral position, which strictly depends on the magnitude of deviations of the movable valve from this position.

Thus, the proposed generator allows, in any of its operating modes, to obtain a stable characteristic 20 of acoustic power with a maximum value of energy conversion efficiency. The displacement mechanism of the movable valve allows the generator to be more efficient when varying the level of the excitation signal and the pressure of the compressed gas in the prechamber.

Claims (1)

Claims of the invention An electropneumatic sound generator comprising a prechamber, one of the walls 30 of which is designed as a sleeve valve with a system of rectangular channels, the distance between which in the axial direction is greater than their height, a valve with the same system of channels located rigidly connected to the causative agent of oscillations located in the air gap of the magnetic system with the excitation winding, and the pre-break chamber, the outlet of which is connected to the horn, and the entrance hole with the valve channels, characterized in that, in order to increase efficiency, a cylindrical waveguide is inserted between the horn and the pre-break chamber, displacement with a drive, connected to the suspension, and a control system for the displacement mechanism, consisting of a power amplifier, the output of which is connected to the electrical input of the drive of the displacement mechanism, and the input - with the output of the first comparator ora, one of the inputs of which is connected to the selector of the constant component of the electric signal, and the other with the selector of the variable component, the inputs of the selectors are connected to the displacement sensor mounted on the movable valve, the output of the selector of the constant component is also connected to one the input of the second comparator, the other input of which is connected to the reference signal extraction unit, and the output to the signal level limiter, the output of which is connected to the input of the excitation winding, wherein the diameter of the cylindrical waveguide is equal predrupornoy chamber diameter and its length is defined by the equation I , 35 tgS (M / K) 1/2, where K - suspension stiffness; M is the reduced mass of the movable valve and the exciter; C - the speed of sound in the air.