CN2373953Y

CN2373953Y - Apparatus for eliminating background noise

Info

Publication number: CN2373953Y
Application number: CN 99200944
Authority: CN
Inventors: 苏庚癸
Original assignee: Jianzhun Electric Machine Industry Co ltd
Current assignee: Jianzhun Electric Machine Industry Co ltd; Sunonwealth Electric Machine Industry Co Ltd
Priority date: 1999-01-26
Filing date: 1999-01-26
Publication date: 2000-04-12
Anticipated expiration: 2009-01-26

Abstract

The utility model relates to an apparatus for eliminating background noise, which comprises an induction circuit and a background noise eliminating circuit, wherein, the induction circuit is provided with two inductors which can induce the background noise, one inductor is positioned in front of a sound source which is to be measured, the input end of the background noise eliminating circuit is connected with the output end of the induction circuit, and the inductor can be a capacitor microphone or a moving-coil microphone with high accuracy and sensitivity. The background noise eliminating circuit can be one differential circuit which can eliminate the common mode background noise values inducted by the two inductors. The apparatus of the utility model has the advantages that cost is low, structure is simple, and an anechoic chamber with high cost does not need to be arranged.

Description

Eliminate the device of background noise

The utility model relates to a kind of device of eliminating background noise.

Generally when the noise in the specific noise source of measurement, inductor will receive environmental noise on every side in the lump, with the noise addition of actual noise source generation, so that measurement result is the wrong numerical value with background noise.If will get rid of the influence of background noise, then an anechoic chamber must be set, inspection machine is put into anechoic chamber, with isolated outside noise, but the cost of anechoic chamber is very high, measures the cost raising to cause.

The purpose of this utility model is to provide the device of the low elimination background noise of a kind of cost.

For the utility model that achieves the above object is taked following measure:

The device of elimination background noise of the present utility model is characterized in that, comprising:

One sensor circuit has two inductors that can respond to background noise, and first inductor places before the source of sound to be measured;

One background noise is eliminated circuit, and its input connects the output of sensor circuit.

The device of described elimination background noise is characterized in that, described inductor is high accuracy and highly sensitive specialty condenser microphone.

The device of described elimination background noise is characterized in that, described inductor is high accuracy and highly sensitive Low ESR moving-coil microphone.

The device of described elimination background noise is characterized in that, it is anti-phase with the background noise of one of them inductor induction that described background noise is eliminated circuit, with the background noise value addition of an inductor induction.

The device of described elimination background noise is characterized in that, it is a differential circuit that described background noise is eliminated circuit, with the common mode background noise value payment of described inductor induction.

Described differential circuit can comprise two operational amplifiers, first operational amplifier that plays inverting function, second operational amplifier that plays amplification; First operational amplifier is connected with first inductor, and second operational amplifier is connected with second inductor; First and second operational amplifier connects.

Description of drawings:

Fig. 1 is a circuit block diagram of the present utility model;

Fig. 2 is the sense state schematic diagram of inductor of the present utility model;

Fig. 3 is that sensor circuit of the present utility model and background noise are eliminated the circuit diagram that circuit connects;

Reaching embodiment in conjunction with the accompanying drawings is described in detail as follows the utility model:

The device of elimination background noise of the present utility model, noise-measuring with fan is that example is illustrated, Figure 1 shows that the circuit block diagram of the utility model embodiment, noise-measuring device of the present utility model comprises a sensor circuit 2, background noise elimination circuit 3 and a signal processing circuit 4; Wherein, sensor circuit 2 has two

inductors

21 and 22, as shown in Figure 2, two inductors all can be sensed background noise, fan 11 to be measured is placed in one before the inductor 21,

inductor

21,22 is the special-purpose condenser microphone or the Low ESR moving-coil microphone of a high precision and high sensitivity, and it has the characteristic of high-gain, low noise.The input of background noise elimination circuit 3 is connected to the output of sensor circuit 2, because of two

inductors

21 and 22 all can be responded to background noise, the background noise value of one of them inductor induction is anti-phase, the background noise value addition of sensing with another tool inductor, then positive and negative offseting, background noise is eliminated circuit 3 through background noise and is eliminated; In addition, it is a differential circuit that background noise is eliminated circuit 3, because of two

inductors

21,22 all can be responded to background noise, so background noise is a common-mode signal, therefore utilizes differential circuit the background noise of common mode can be eliminated; Whether signal processing circuit 4 will be eliminated the noise signal of the fan 11 of background noise, handle through appropriate signals, qualified to differentiate fan noise to be measured; Signal processing circuit 4 comprises a signal rectifier circuit 41, a dc amplification circuit 42, a comparator decision circuit 43 and result of determination display circuit 44.The fan noise signal rectification that signal rectifier circuit 41 will be eliminated background noise is the direct current noise signal; Dc amplification circuit 42 amplifies the direct current noise signal after the rectification again; Noise signal after amplification size is directly proportional with actual noise, and this comparator decision circuit 43 has one with reference to accurate position, when noise signal greater than this with reference to accurate position, then have the noise of signal output demonstration fan 11 defective; Result of determination display circuit 44 just shows whether the noise of fan 11 is qualified.

The circuit diagram of the utility model embodiment is as follows, and Fig. 3 is the circuit diagram that sensor circuit 2 of the present utility model and background noise are eliminated circuit 3, divides two kinds of situation discussion:

(1) when background noise exists, inductor 21 in the circuit diagram and inductor 22 are all responded to background noise simultaneously, amplify and carry out differential function and enter operational amplifier 31 and 32.Such as background noise e0 respectively by inductor 21 and inductor 22 induction, through operational amplifier 31, again because resistance 33 equals resistance 34, so the output of operational amplifier 31 is-e0, this-e0 signal output is sent to the A point via resistance 35, with the signal e0 addition of inductor 22 inductions.So the signal voltage of ordering at A be e0+ (e0)=0, the voltage after this addition still is 0 output voltage through operational amplifier 32, i.e. e2=0, promptly background noise e0 is eliminated.

(2) fan to be measured 11 is placed on before the inductor 21, then at this moment, the noise of fan 11 is through operational amplifier 31, output to the A point, this voltage is made as (e1), and inductor 22 is owing to can't sense the noise of fan 11, so the fan noise of inductor 22 equals 0, the voltage that this moment, A was ordered is and (e1)+0, equals (e1).(fan noise e1) is output as e2 via operational amplifier 32 back amplifications, and this e2 has been the noise signal of the fan 11 of eliminating background noise for this.

The device of elimination background noise of the present utility model, must eliminate the background noise part for being used in, the device of this elimination background noise must not be provided with expensive anechoic chamber, can with low-cost, simply and again circuit arrangement is eliminated background noise accurately, this eliminations background noise device comprises: a sensor circuit and background noise elimination circuit; Sensor circuit has two inductors, two inductors all can be sensed background noise, source of sound to be measured is placed in one before the inductor, inductor be the specialty of a high precision and high sensitivity with condenser microphone or low-impedance moving-coil microphone, it has the electrical characteristics of high-gain, low noise; The input of background noise elimination circuit is connected to the output of sensor circuit, in order to eliminate the background noise in the input noise, because of two inductors all can be responded to background noise, the background noise value that one of them inductor receives is anti-phase, background noise value addition with another inductor induction, then positive and negative offseting, background noise is eliminated circuit for eliminating through background noise, therefore the exportable level of noise actual to be measured that does not contain background noise; In addition, background noise is eliminated circuit can utilize differential circuit, because of two inductors all can respond to background noise, so background noise is a common-mode signal, so utilize the differential circuit can be with the background noise elimination of common mode.

Compared with prior art, the utlity model has following effect:

Device of the present utility model, cost is low, simple in structure, measures accurately, height need be set The anechoic room of cost can be measured correct noise value, gets rid of simultaneously the impact of background noise.

Claims

1, a kind of device of eliminating background noise is characterized in that, comprising:

2, the device of elimination background noise according to claim 1 is characterized in that, described inductor is high accuracy and highly sensitive specialty condenser microphone.

3, the device of elimination background noise according to claim 1 is characterized in that, described inductor is high accuracy and highly sensitive Low ESR moving-coil microphone.

4, the device of elimination background noise according to claim 1 is characterized in that, it is anti-phase with the background noise of one of them inductor induction that described background noise is eliminated circuit, with the background noise value addition of an inductor induction.

5, the device of elimination background noise according to claim 1 is characterized in that, it is a differential circuit that described background noise is eliminated circuit, with the common mode background noise value payment of described inductor induction.