SU836652A1 - Noise suppressing device - Google Patents

Description

one

The invention relates to the field of instrumentation and can be used in the manufacture of devices for noise suppression.

A device for suppressing a puma is known, comprising a microphone, an amplifier p and a loudspeaker. The phase response of this device is adjusted according to the output of the microphone, creating oscillations that are out of phase with the noise of the rn noise signal.

However, this device does not provide effective suppression of schum.

It is also known a device for suppressing noise, comprising a microphone located in the air BETTER of a fan, as well as an amplifier connected in series to the microphone, filters, an adder and loudspeakers that reproduce a signal shifted in fae by 180 ° relative to the signal at the location of the microphone b .

A disadvantage of this device is also the inadequate efficiency of noise suppression due to the fact that both direct and reflected waves act on the microphone, as well as due to the influence of the standing waves caused by the air duct.

The aim of the invention is to increase the effectiveness of noise suppression.

The goal is achieved

0 due to the fact that the outlet part of the duct is provided with a matching sound-absorbing element, the outer shell in the longitudinal section has the shape of an exponential horn.

S

On 4ig. 1 shows a structural diagram of a device for suppressing noise; in fig. 2 - the design of the matching exponential horn.

The noise suppressor comprises a microphone 1, an acoustic channel 2, an amplifier 3, filters 4, an adder 5, a speaker 6, and a matching device 7.

The device works as follows.

 1 set, s to such a point of channel 2, where the audio signal has a phase different from the phase of the audio signal propagating along the channel. The 1st I microphone perceives the sound that is amplified by the amplifier 3, the amplifier 3 receives the signal from the filters 4 and then to the adder. (The signal from adder 5 is reproduced by speakers 6. This signal differs in phase by 180 from the signal perceived by microphone 1. By introducing an exponential horn 7, which is an airway matching device, there is no reflected and standing WOL1P4 in the sound range

frequencies. In the air duct 6vneT, there is a straight wave,

which is first perceived by the micro background 1 and then suppressed by the antiphase signal using the speaker 6. As a matching device, an end absorber can be introduced, shown in

FIG. 2

The end absorber consists of a frame 8, made in the form of a conical horn made of perforated steel sheet I mm with a perforation factor of 35%, and a casing 9 made of plywood 10 mm thick, having contours of an exponential horn. The cavity between the frame and the casing 10 is filled with sound-absorbing material. To prevent the spread of sound by sounding 366524

the spreading material its layer of variable thickness is divided by transverse partitions P.

Thus, due to the introduction of the J matching element, the described device provides effective noise suppression due to the fact that only a straight wave is present in the duct and no reflected and standing waves occur.

Claims (2)

1. Published Japanese Application No. 15-46401, cl. G 10 K 1.1 / 02, .1977. 2. Published in UK No. 1492963, cl. G 10 K P / 00, 1978 (prototype.;