JP3061805U - Noise measurement device - Google Patents

Abstract

(57) [Problem] To provide a noise measuring device capable of accurately measuring actual noise with a low-cost, simple, and precise device. A noise measuring device is a sensor circuit having two sensors for detecting ambient noise, a sensor circuit in which a noise source to be tested is arranged in front of one of the sensors, and a peripheral noise removing circuit. A peripheral noise removing circuit in which an input terminal of the circuit is connected to an output of the sensor circuit, and appropriately processing noise other than the removed peripheral noise, thereby determining whether the noise is acceptable Signal processing circuit.

Description

[Detailed description of the invention]

[0001]

[Technical field to which the invention belongs]

 The present invention relates to a noise measuring device, and particularly to a device for measuring noise generated by a fan.

[0002]

[Prior art]

 When measuring noise sources, the sensor detects ambient noise and the actual noise from the noise source. Measurements containing ambient noise are inaccurate, so an anecoic room is needed to eliminate interference due to ambient noise.

[0003]

[Problems to be solved by the invention]

 However, in order to isolate external noise, noise measurement equipment must be installed in an anechoic room, and the cost of installing such an anechoic room is very high.

[0004] Therefore, it has been desired to provide a novel device for accurately measuring actual noise without surrounding noise.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a noise measuring device, thereby reducing actual noise with a low-cost, simple, and precise device. It is to measure accurately.

Another object of the present invention is to provide a noise measuring device, which eliminates ambient noise without requiring an expensive anechoic chamber in a low-cost, simple and precise device. That is.

[0007]

[Means for Solving the Problems]

 The noise measuring device of the present invention is a sensor circuit having two sensors for detecting peripheral noise, wherein a noise source to be tested is arranged in front of one of the sensors, and a sensor circuit and a peripheral circuit. A noise elimination circuit, wherein an input terminal of the circuit is connected to an output of the sensor circuit, and a peripheral noise elimination circuit that appropriately processes noise other than the eliminated peripheral noise; And a signal processing circuit for determining whether or not the signal is permissible, thereby achieving the above object.

[0008] The sensor may be a dedicated capacitor microphone having high accuracy and sensitivity.

[0009] The sensor may be a moving coil microphone having low impedance and high accuracy and sensitivity.

The peripheral noise removing circuit reverses the phase of the peripheral noise from one of the sensors, and then adds the peripheral noise from the other sensor, thereby removing the peripheral noise. There may be.

The peripheral noise removing circuit may be a differential circuit that removes common mode peripheral noise from the two sensors.

The signal processing circuit performs a comparison between a signal rectifier circuit that rectifies the removed peripheral noise signal into a DC noise signal, a DC amplifier circuit that amplifies the DC noise signal, and a comparison between the amplified DC noise signal. A comparison circuit having a reference level to perform, and outputting a signal indicating that the noise is not acceptable when the amplified DC noise signal is greater than the reference level.

Alternatively, the peripheral noise elimination device of the present invention is a sensor circuit having two sensors for detecting ambient noise, wherein a noise source to be tested is arranged in front of one of the sensors. A sensor circuit and a peripheral noise elimination circuit having an input terminal of the circuit connected to an output of the sensor circuit, thereby achieving the above object.

The sensor may be a dedicated capacitor microphone having high accuracy and sensitivity.

The sensor may be a moving coil microphone having low impedance and high accuracy and sensitivity.

The peripheral noise elimination circuit reverses the phase of the peripheral noise from one of the sensors, and then adds the peripheral noise from the other sensor, thereby removing the peripheral noise. There may be.

The peripheral noise removing circuit may be a differential circuit that removes common mode peripheral noise from the two sensors.

[0018]

[Embodiment of the invention]

 As an embodiment of the present invention, an apparatus for measuring noise from a fan is shown. FIG. 1 shows a circuit block diagram according to the present invention. The noise measuring device includes a sensor circuit 2, a peripheral noise removing circuit 3, and a signal processing circuit 4. Referring to FIG. 2, the sensor circuit 2 includes two sensors 21 and 22. Both sensors 21 and 22 can detect ambient noise. The fan 11 to be tested is installed in front of the sensor 21. The sensors are dedicated capacitor type microphones with high precision and sensitivity, or moving coil microphones with low impedance and high precision and sensitivity. However, the sensor exhibits high gain and low noise characteristics.

An output of the sensor circuit 2 is connected to an input of the peripheral noise elimination circuit 3. Since both the sensors 21 and 22 can detect the peripheral noise, it is necessary to remove the peripheral noise by inverting the phase of the peripheral noise value from one of the sensors and adding the peripheral noise value from the other sensor. Can be. Therefore, the peripheral noise is removed by the peripheral noise removing circuit. Further, a differential circuit can be used as the peripheral noise elimination circuit. The peripheral noise is related to the common mode signal because both sensors 21 and 22 can detect the peripheral noise. Therefore, common mode peripheral noise can be eliminated by the differential circuit.

The signal processing circuit 4 determines whether or not the noise is allowable by appropriately processing the removed peripheral noise. The signal processing circuit 4 includes a signal rectification circuit 41, a DC amplification circuit 42, a comparison circuit 43, and a result display circuit 44. The fan noise signal that does not include the peripheral noise is rectified into a DC noise signal by the signal rectification circuit 41, and the DC noise signal is amplified by the DC amplification circuit 42. The amplitude of the amplified DC noise signal is proportional to the actual noise. The comparison circuit 43 gives a reference level. If the amplified DC noise signal exceeds its reference level, a signal is output indicating that the noise is unacceptable. The result display circuit 44 indicates whether the fan noise is acceptable.

In order to further understand the present invention, circuit diagrams will be described below. FIG. 3 is a circuit diagram showing the sensor circuit and the peripheral noise removing circuit according to the present invention. The following two cases will be described.

(1) When peripheral noise occurs, both the sensors 21 and 22 shown in FIG. 3 detect the peripheral noise, and the same peripheral noise signal is amplified by operational amplifiers 31 and 32. For example, an ambient noise signal (e0) is detected by each of the sensor 21 and the sensor 22, and passes through the operational amplifier 31. Since the resistor 33 is equal to the resistor 34, the output of the operational amplifier 31 is (-e0). The output of the operational amplifier 31 is connected to a point (A) through a resistor 35. The sum of the signal (−e0) and the signal (e0) from the sensor 22 is 0, and the voltage at the point (A) is obtained by e0 + (− e0) = 0, and becomes 0. The output of the operational amplifier 32 is 0 (e2 = 0) even if the signal at the point (A) passes through the operational amplifier 32. Thus, the peripheral noise signal (e0) is removed.

(2) The fan 11 is installed in front of the sensor 21. The fan noise signal that has passed through the operational amplifier 31 is output to point (A). The voltage at point (A) is (-e1). The sensor 22 cannot detect fan noise, and the fan noise signal from the sensor 22 is zero. The voltage at point (A) is (-e1) +0, and is therefore equal to (-e1). The signal (-e1) that has passed through the operational amplifier 32 is amplified and becomes a signal (e2) that does not include peripheral noise.

FIG. 4 shows a signal rectifier circuit and a DC amplifier circuit. Referring to FIG. 4, full-wave rectification is achieved by the op amp 51. The input of the operational amplifier 51 is connected to the output signal (e2) (AC signal) of the operational amplifier 32 shown in FIG. The resistor 52 and the resistor 53 are gain control resistors. Resistor 54 and resistor 55 function as a bias for operational amplifier 51, which allows full-wave rectification of the AC signal without interruption which would result in erroneous results. Capacitor 56 functions as a bias filter and provides a smooth bias to operational amplifier 51. The diodes 57 and 58 function as rectifier diodes. The rectified DC voltage is amplified and filtered through an operational amplifier 59. Thereby, a smooth DC voltage output (e3) is obtained.

FIG. 5 shows a comparison circuit diagram according to the present invention. The amplitude of the voltage (e3) from the output of the operational amplifier 59 is proportional to the actual noise. The higher the noise, the higher the DC voltage (e3) is obtained. The lower the noise, the lower the DC voltage (e3) is obtained. FIG. 5 shows an adjustable reference voltage that determines whether noise is acceptable. In FIG. 5, the signal (e3) is the input voltage. The operational amplifier 61 functions as a comparator. The adjustable resistor 62 allows the DC voltage level (Vref) to be set below the level at which fan noise is acceptable. If e3> Vref, the operational amplifier 61 outputs a DC voltage. Therefore, as the value of e3 (> Vref) increases, the output of the operational amplifier 61 increases proportionally. The operational amplifier 63 functions as a buffer for the output DC voltage. If the signal (e3) is higher than the reference voltage, the circuit outputs a result (e4). The signal (e4) is proportional to the noise. If the signal (e3) is lower than the reference voltage, the circuit outputs a result (e4 = 0). Based on the signal (e4), it can be determined whether the noise is acceptable.

FIG. 6 shows a result display circuit of the present invention. The LEDs 71, 72, 73, 74, or 75 are sequentially turned on according to the amplitude of the signal (e4). When the signal (e4) is minimum, the LED 71 is turned on. When the signal (e4) is the maximum, the LED 75 is turned on. LEDs 71, 72, and 73 display green to indicate that fan noise is acceptable. LED 74 displays a yellow color indicating that fan noise is generally unacceptable but marginally acceptable. LED 75 displays a red color indicating that the fan noise is too loud and unacceptable. The colors shown on the LEDs indicate whether the noise is acceptable.

The present invention also provides an apparatus for removing ambient noise. Therefore, an expensive anechoic chamber is not required. Ambient noise eliminators can eliminate ambient noise with low cost, simple, and precise equipment. The peripheral noise removing device includes a sensor circuit and a peripheral noise removing circuit. The sensor circuit includes two sensors, both of which can detect ambient noise. In use, place the noise source in front of one of the sensors. The sensors are either dedicated capacitor microphones with high accuracy and sensitivity, or moving coil microphones with low impedance and high accuracy and sensitivity, and also have high gain and low noise characteristics. In use, the input of the peripheral noise elimination circuit is connected to the output of the sensor circuit, and the peripheral noise is eliminated. Since both sensors can detect ambient noise, the ambient noise can be removed by inverting the phase of the ambient noise value from one of the sensors and adding the ambient noise value from the other sensor. Further, the differential circuit can be used as a peripheral noise removing circuit. The ambient noise is a common mode signal because both sensors can detect the ambient noise. Thereby, the common mode peripheral noise can be removed by the differential circuit.

As described above, in the present invention, the noise measuring device uses a sensor circuit for detecting a noise source. The sensor circuit includes two sensors, both of which can detect ambient noise. The noise source under test is placed in front of one of the sensors. The output of the sensor circuit is connected to the input of the peripheral noise elimination circuit, and the peripheral noise is eliminated by the peripheral noise elimination circuit. The noise signal without ambient noise is connected to a signal processing circuit and processed appropriately to determine whether the noise is acceptable.

[0029]

[Effect of the invention]

 According to the present invention, it is possible to realize a noise measuring device using a low-cost, simple, and precise electronic circuit. There is no need to install an expensive anechoic chamber, and the circuit according to the present invention can accurately measure noise and eliminate interference due to surrounding noise.

Further, according to the present invention, there is provided a peripheral noise removing apparatus which can eliminate peripheral noise by a low-cost, simple, and precise device which does not require an expensive anechoic chamber.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of the present invention.

FIG. 2 is a diagram illustrating the operation of the sensor according to the present invention.

FIG. 3 is a circuit diagram showing a connection of a peripheral noise elimination circuit and a sensor according to the present invention.

FIG. 4 is a circuit diagram showing the connection of the signal rectifier circuit and the DC amplifier circuit according to the present invention.

FIG. 5 is a diagram illustrating a comparison circuit according to the present invention.

FIG. 6 is a diagram showing a result display circuit according to the present invention.

[Explanation of symbols]

 Reference Signs List 2 sensor circuit 3 peripheral noise removing circuit 4 signal processing circuit 21, 22 sensor 11 fan 31, 32, 51, 59, 61, 63 operational amplifier 33, 34, 35, 52, 53, 54, 55 resistor 41 signal rectifying circuit 42 DC amplification circuit 43 Comparison circuit 44 Result display circuit 56 Capacitor 57, 58 Diode 62 Adjustable resistor 71, 72, 73, 74, 75 LED

Continuation of front page (73) Utility model holder 599028652 No. 3, LANE 45, Yi-Yung Road, Kaohsiung, Taiwan, R.A. O. C.

Claims (11)

[Utility model registration claims] 1. A sensor circuit having two sensors for detecting ambient noise, wherein a noise source to be tested is arranged in front of one of the sensors, and a peripheral noise removal circuit. A peripheral noise removing circuit, wherein an input terminal of the circuit is connected to an output of the sensor circuit, and appropriately processing noise other than the removed peripheral noise,
Thus, a signal processing circuit for determining whether the noise is acceptable or not is provided. 2. The apparatus according to claim 1, wherein the sensor is a dedicated capacitor microphone having high accuracy and sensitivity. 3. The apparatus of claim 1, wherein the sensor is a moving coil microphone having low impedance and high accuracy and sensitivity. 4. The peripheral noise elimination circuit inverts a phase of the peripheral noise from one of the sensors, and thereafter,
Add the ambient noise from the other sensor, which
The apparatus of claim 1, wherein the apparatus removes ambient noise. 5. The apparatus according to claim 1, wherein the peripheral noise removing circuit is a differential circuit that removes common mode peripheral noise from the two sensors. 6. A signal rectifier circuit, wherein the signal processing circuit rectifies the removed peripheral noise signal to obtain a DC noise signal, a DC amplifier circuit for amplifying the DC noise signal, A comparison circuit having a reference level for performing the comparison, and outputting a signal indicating that the noise is not acceptable when the amplified DC noise signal is larger than the reference level. The device according to claim 1. 7. A sensor circuit having two sensors for detecting ambient noise, wherein a noise source to be tested is arranged in front of one of the sensors, and a peripheral noise removal circuit. A circuit having an input terminal of the circuit connected to an output of the sensor circuit. 8. The apparatus according to claim 7, wherein the sensor is a dedicated capacitor microphone having high accuracy and sensitivity. 9. The apparatus according to claim 7, wherein the sensor is a moving coil microphone having low impedance and high accuracy and sensitivity. 10. The peripheral noise elimination circuit inverts the phase of the peripheral noise from one of the sensors, and then adds the peripheral noise from the other sensor, thereby eliminating the peripheral noise. Item 8. The apparatus according to Item 7. 11. The apparatus according to claim 7, wherein the peripheral noise removing circuit is a differential circuit that removes common mode peripheral noise from the two sensors.