JPH07192183A - Abnormal sound inspection device - Google Patents

Abstract

PURPOSE:To reduce noises from noise sources other than an object noise source. CONSTITUTION:Microphones 1 and 2 are arranged at an equal distance from the noise source 31 and at different positions where the directions in which they are the same in phase and have maximum gain, are opposite to each other, and, the outputs of the microphones 1 and 2 are applied to a phase spectrum measurement part 4 and a power spectrum measurement part 9. A phase spectrum S1 as a frequency distribution of phase differences between the microphones 1 and 2 is outputted from the phase spectrum measurement part 4, and a power spectrum S2 which is the spectrum sum of the outputs of the microphones 1 and 2 is outputted from the power spectrum measurement part 9, and, an object phase difference detection part 6 generates a frequency range S3 in the range of the values of two phases stored in a detection phase storage part 5. A frequency level distribution extraction part 7 extracts only components which are in the power spectrum and in its frequency range and outputs them as a monitor signal S4. A level decision part 8 outputs an alarm signal when the monitor signal S1 exceeds a certain predetermined level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abnormal sound inspection device,
In particular, the present invention relates to an abnormal sound inspection device that detects non-stationary noise other than stationary noise generated by an inspection target.

[0002]

2. Description of the Related Art As a device to which an abnormal sound detection method used in a conventional abnormal sound inspection device of this type is applied, there is a magnetic disk device disclosed in Japanese Patent Laid-Open No. 2-307383. This device is equipped with a noise level converter, an abnormal sound detection circuit that monitors changes in the output of this noise level converter, and an interface circuit that outputs an alarm signal in the event of an abnormality. When it is different from usual, it detects it as an abnormal sound and outputs an alarm signal.

As another conventional abnormal sound inspection device, there is an abnormal noise vehicle detection device disclosed in Japanese Patent Laid-Open No. 3-113599.

This device comprises an acoustic sensor for detecting the level of a sound emitted from a vehicle, and a spectrum detector for detecting the spectrum of the sound when the level of the sound exceeds a predetermined level. Section and an abnormal noise judgment circuit that compares the frequency spectrum unique to the emergency vehicle with the spectrum of the input external sound, and if the difference between both spectra is outside the predetermined reference range by this abnormal noise judgment circuit. For example, a warning is issued, and if it is within the above-mentioned reference range, it is determined not to be an abnormal sound but to be the noise of the passage of the emergency vehicle or the ambient noise outside the emergency vehicle.

[0005]

In the magnetic disk device to which the above-mentioned conventional abnormal sound inspection method is applied, a certain reference level that can be regarded as stationary noise is set in advance, and the level of the incoming sound exceeds this reference level. When it does, it is determined to be an abnormal sound. Therefore, a device that generates noise other than the abnormal sound detection target or other non-abnormal sound detection target approaches the part that detects this noise, and the level is higher than the steady noise generated by the inspection target. If a large amount of noise is generated, there is a disadvantage that an erroneous alarm may be output due to the noise generated by an article that is not the target of detection of this abnormal sound.

Further, in order to prevent the above-mentioned alarm from being generated even when such an external non-inspection object approaches, in order to prevent the above-mentioned alarm from being generated, the surroundings of the sensor for detecting noise from the surroundings other than the object are detected. Since it is necessary to provide a soundproof structure for shielding noise, there is a drawback that the device becomes large.

Further, in the above-mentioned abnormal noise vehicle detection device, when the noise level exceeds the reference level, the spectrum of the acoustic data generated by the emergency vehicle is compared with the spectrum stored in advance, and both are compared. When the spectrum level difference exceeds a certain value, it is determined that the target vehicle that is generating noise is a runaway vehicle.Therefore, there are multiple types of emergency vehicles, which are stored in advance as the number of types increases. Since the number of spectrums to be kept increases, the device becomes complicated, and when the noise level coming into this device from other than the vehicle is higher than the reference level, each time such noise comes in, the above-mentioned Since the spectrum comparison process is performed, it has a drawback that it takes time to determine whether the sound is abnormal.

[0008]

SUMMARY OF THE INVENTION An abnormal sound inspection apparatus according to the present invention has detection units arranged at positions different from each other by an equal distance from a noise source of interest, and has an 8-shaped directivity and equal polarities. Of the first and second microphones arranged so that the directions having the maximum gains of 1 and 2 are opposite to each other and different from the direction of the noise source, and the outputs of the first and second microphones are input to the first microphone. And a phase spectrum measuring section that measures the phase difference between the outputs of the second microphones for each frequency component and outputs as a phase spectrum, a first phase value given in advance,
A detection phase storage unit for storing a second phase value having a value larger than the first phase value; and reading the first phase value and the second phase value when the phase spectrum is input, A target phase difference detection unit that detects and outputs a frequency region that is greater than or equal to the first phase value and less than or equal to the second phase value in the phase spectrum, and outputs of the first and second microphones in vector form. A power spectrum measurement unit that combines and measures the power level of each frequency component and outputs as a power spectrum, and inputs the power spectrum and the frequency domain, and from the power spectrum, only frequency components within the frequency domain are input. A frequency level distribution extraction unit that extracts and outputs as a monitoring signal, a decision level that is input and receives the monitoring signal, and a level of the monitoring signal that is stored in advance. It is constituted by a level determination unit for outputting an alarm signal to an external when the level of the monitoring signal is compared with the Le exceeds the judgment level.

[0009]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the abnormal sound inspection apparatus of the present invention.

As shown in FIG. 1, the abnormal sound inspection apparatus according to the present embodiment is arranged around a noise source 31 that generates the largest level of noise in the inspection object 3 with respect to the inspection object 3. Microphones 1 and 2 for converting the received and incoming noise into electric signals, and a phase spectrum measuring unit 4 for measuring and outputting the phase spectrum S1 of the input electric signals by inputting the outputs of the microphones 1 and 2 Article 3
Of the stationary noise generated by the noise source 31 of FIG. 1 is measured in advance, and based on the result, the detected phase storage unit 5 which stores in advance the first phase value and the second phase value to be extracted. And a target position for calculating and outputting a frequency region having a phase within the range of the first phase value and the second phase value stored in the detected phase storage unit 5 from the output of the phase spectrum measuring unit 4. A phase difference detection unit 6, a power spectrum measurement unit 9 that receives the output of the microphone 1 and the output of the microphone 2 as inputs, combines these two in vector, measures the power spectrum of the combined signal, and outputs the power spectrum, and measures the power spectrum. Power spectrum S output by section 9
2 and the frequency region S3 output by the target phase difference detection unit 6 are input, and the frequency level distribution extraction unit 7 outputs only the power spectrum component corresponding to the frequency region input from the power spectrum S2 as the monitoring signal S4. And a level of the monitoring signal S4 that is compared with the level of the monitoring signal S4, which is stored in advance with the monitoring signal S4 as an input, and a level at which an alarm is output to the outside when the level of the monitoring signal S4 exceeds the determination level. The determination unit 8 is provided.

FIG. 3 is an illustration of an example of directivity of the microphones 1 and 2. In FIG. 3, L1 is a directional curved surface showing the directivity with the positive direction of the X axis as the maximum gain direction, and L2 is a directional curved surface showing the directivity with the negative direction of the X axis as the maximum gain direction. Directional curved surfaces L1 and L indicating directivity
Both 2 are objects to be rotated with respect to the X axis.

Further, the first sound source of the two sound sources having the same intensity, the same phase and the same frequency, which are separated from the origin O of the coordinate system of FIG. 3 by an equal distance, is arranged on the extension of the X-axis direction, The other second sound source is arranged in the negative direction of the X-axis, and the first sound source is first operated and the level of the output received by this microphone is a positive level. When only the sound source of 2 is operated, the absolute value of the output level of the microphones 1 and 2 is the first
The same as when only the sound source of is operated, but the polarity is negative.

In addition, the above-mentioned first sound source is 90 degrees from the X axis.
The microphone is placed in a direction inclined by an angle θ less than a degree, and the polarity of the output level of the microphone with respect to this sound source is positive.
The second sound source is placed at a tilted position, and at the same time as the first sound source, the level of the microphone output by this sound source is equal to the level when the sound source 1 is operated, and its polarity is negative. Set the characteristics of the microphones 1 and 2 in advance.

Further, the microphone 1 or 2 is
The gain is 0 in the plane orthogonal to the axis parallel to the maximum gain direction.

The characteristic of the microphone having such directivity will be hereinafter referred to as a figure eight characteristic.

FIG. 2 shows the microphones 1 and 2 shown in FIG.
It is explanatory drawing which shows the arrangement | positioning relationship between and the noise source 31.

Each of the microphones 1 and 2 shown in FIG. 2 has the 8-shaped characteristic shown in FIG. 3 as a directional characteristic.

The X-axis direction (positive) shown in FIG. 3 of the microphone 1 shown in FIG. 2 is made to coincide with the A direction in FIG.
The microphone 2 shown in FIG. 3 has the X-axis direction shown in FIG. 3 coincident with the B direction shown in FIG. 2 and a space is provided between the microphones 1 and 2, so that the detection unit 1A of the microphone 1 and the noise source 31 are separated from each other. The distance between them is equal to the distance between the detection unit 2A of the microphone 2 and the noise source 31.

It is desirable that the distance between the detection unit 1A of the microphone 1 and the detection unit 2A of the microphone 2 be sufficiently small with respect to the wavelength of the noise source to be measured.

The above-mentioned A and B directions are parallel and opposite to each other. When the outputs of the microphones 1 and 2 arranged in this way are combined in a vector manner, the sound sources equidistant from the tips of the microphones 1 and 2 are in phase with each other, and the output level is higher than the output from only one of the microphones. Becomes

When the noise source is in the A direction or the B direction, the polarities of the outputs of the microphones 1 and 2 are opposite to each other, and only one of the microphones 1 or 2 can synthesize the outputs. The level is smaller than when the above noise source is received.

That is, by inputting a composite of the outputs of the microphones 1 and 2 at the input side of the power spectrum measuring unit 9 of FIG. 1, the amount of unnecessary noise from other than the target noise source 31 is reduced. Can be reduced.

FIG. 4 is a waveform diagram for explaining the output relationship of the main components shown in FIG.

Phase spectrum measuring section 4 shown in FIG.
Measures the phase difference for each frequency component of the outputs of the microphones 1 and 2, and outputs the value of the phase difference for each frequency to the target phase difference detection unit 6 as the phase spectrum S1.

In the detected phase storage unit 5, for example, the microphones 1 and 2 of FIG. 1 are arranged with respect to the noise source 31 as shown in FIG. On the basis of the result measured in advance in the first reference phase P1 as shown in FIG.
Then, the value of the second reference phase P2 having a larger value than the first reference phase P1 is determined and stored.

Usually, the value of the first reference phase may be slightly smaller than 0 degree, and the value of the second reference phase may be slightly larger than 0 degree.

The target phase difference detector 6 detects the phase spectrum S
1 is received, the first phase stored in the detected phase storage unit 5
Value of the first reference phase P1 in the phase spectrum S1 with reference to the values of the reference phase P1 and the second reference phase P2 of
A frequency region S3 that is equal to or greater than 1 and equal to or less than the second reference phase P2 is calculated and output.

The frequency domain S3 is, for example, the domain from the frequencies f1 to f2, the domain from the frequencies f3 to f4 and the domain from the frequencies f5 to f6 in FIG.

At the same time that the phase spectrum measuring section 4 outputs the above-mentioned phase spectrum S1, the power spectrum measuring section 9 also synthesizes the outputs of the microphones 1 and 2 in a vector manner. The power spectrum S2 indicating the power level is measured and output.

The frequency level distribution extraction unit 7 receives the power spectrum S2 and the frequency domain S3 as input, extracts only the frequency component within the frequency domain designated by the frequency domain S3 in the power spectrum S2, and monitors the frequency component. Output as signal S4.

The level determination unit 8 has a storage unit (not shown), and stores a predetermined determination level P3 value in this storage unit.

When the monitoring signal S4 is input to the level determining section 8, the level of the monitoring signal S4 changes to the determination level P3.
If the level of the monitoring signal S4 exceeds the value of the determination level P3, a predetermined alarm signal is output to the outside.

In the above embodiment, the case where two microphones are used has been described. It is also possible to arrange four or more microphones at different positions to further reduce noise from unnecessary noise sources other than the noise source of interest.

[0035]

As described above, according to the abnormal sound inspection apparatus of the present invention, the two microphones are arranged such that the directions of outputting the in-phase level at the maximum gain thereof are opposite to each other, and
These microphones are placed equidistant from the noise source of interest, and when measuring the power spectrum, the effect of unwanted noise sources is reduced, and the phase spectrum of the output from these two microphones is reduced. Only the region containing the frequency component that has a specific phase relationship is selected for measurement, and only the power spectrum component that exists within this selected frequency region is used as the monitoring signal, so it is possible to select a different point other than the target noise source. Since the ratio of existing unnecessary noise source components mixed into the monitoring signal can be reduced compared to the conventional noise inspection device of this type or above, there is no chance of malfunction due to unnecessary noise sources other than the target noise source. It has the effect that it can be reduced.

Further, since it is not necessary to mechanically shield the noise coming from the unnecessary noise source, there is an effect that the apparatus can be made compact.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an abnormal sound inspection device of the present invention.

FIG. 2 is an explanatory diagram showing a positional relationship between the microphones 1 and 2 and a noise source 31 shown in FIG.

FIG. 3 is an explanatory diagram of an example of directivity of the microphones 1 and 2 shown in FIG.

FIG. 4 is a waveform diagram illustrating the output relationship of the main components shown in FIG.

[Explanation of symbols]

 1 Microphone 2 Microphone 3 Object to be inspected 4 Phase spectrum measurement section 5 Detected phase storage section 6 Target phase difference detection section 7 Frequency level distribution extraction section 8 Level judgment section 9 Power spectrum measurement section 31 Noise source

Claims (1)

[Claims] 1. The noises are arranged such that the detection units are arranged at positions different from each other at an equal distance from the noise source of interest, and the directions having a figure 8 shape and the maximum gains of equal polarity are opposite to each other. A first and a second microphone arranged so as to have directions different from those of the source, and a phase difference between the outputs of the first and the second microphones, which is an input to the outputs of the first and the second microphones. A phase spectrum measuring unit for measuring and outputting as a phase spectrum for each time, a detected phase memory for storing a first phase value given in advance and a second phase value having a value larger than the first phase value. And a frequency region in which the first phase value and the second phase value are read when the phase spectrum is input and which is greater than or equal to the first phase value and less than or equal to the second phase value in the phase spectrum. Phase to detect and output A difference detection unit, a power spectrum measurement unit that vectorally combines the outputs of the first and second microphones, measures the power level for each frequency component, and outputs as a power spectrum, the power spectrum, and the frequency region. , A frequency level distribution extraction unit that extracts only the frequency components in the frequency domain from the power spectrum and outputs the signal as a monitoring signal, and a determination level that is given in advance and stored as the monitoring signal. And a level determination unit that compares the level of the monitoring signal with the level of the monitoring signal and outputs an alarm signal to the outside when the level of the monitoring signal exceeds the determination level.