JPH06315197A - Rattle sound detecting device - Google Patents

Abstract

PURPOSE:To provide a rattle sound detecting device in which the rattle sound of an electroacoustic transducer can be automatically and highly precisely detected at a practical processing speed. CONSTITUTION:50-500Hz sweep sine wave is inputted from a signal source 11 to a compact head phone 13 under the control of a compact computer 12, and the output acoustic signal is received in sound through a coupler 14 by a microphone 15, amplified by an amplifier 16, and fetched in the compact computer 12. In the compact computer 12, the input signal is converted into a digital signal by an A/D converter 17, inputted to a digital filter 18, and digitally processed, so that rattle components can be extracted. The digital filter 18 is optimized so that the rattle sound of the head phone can be the most easily detected, and even the faint rattle sound can be extracted. The rattle components are arithmetically processed by an arithmetic processing discriminating means 19, and an evaluation value indicating the rattle degree is calculated, and compared with a preliminarily decided reference value, and a normal/defective condition is discriminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abnormal audible noise generated from an electroacoustic transducer such as headphones or a speaker,
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soothing noise detecting device for detecting soothing noise, and particularly, it is possible to automatically and highly accurately detect the soothing noise at a practical processing speed by using an inexpensive small computer such as a personal computer. The present invention relates to a clinging sound detection device.

[0002]

2. Description of the Related Art A chattering noise is generated in an electroacoustic transducer such as a speaker or a headphone when a diaphragm or a coil comes into contact with another component or a foreign substance is mixed in a gap between the coil and the magnet. It is an abnormal sound. This chattering noise often occurs when the input frequency is relatively low. In this case, the main frequency component of the chattering sound exists in an extremely high frequency band. For example, in the case of small headphones, the input frequency at which the chattering sound is generated is 50.
The frequency spectrum of the clinging sound itself is widely distributed in the range of 5 to 20 KHz, although it is almost 0 Hz or less. Therefore, it is impossible to detect even by examining the harmonic distortion rate. However, this abnormal sound should not occur because it can be heard very well by humans.

Since the level of the chattering sound is extremely low as compared with the level of the input sound, it is difficult to automatically detect the chattering sound. Therefore, conventionally, a sine wave signal that sweeps from DC to 20 KHz is input to the inspected electroacoustic transducer as an inspection signal, and the inspector actually listens to the sound generated from the inspected electroacoustic transducer and there is an abnormality. Most of the time, it is looking for none.

[0004]

In the conventional inspection based on the auditory sense of an inspector, it takes time and labor to perform the inspection, and the inspector has different judgment criteria. Even the same inspector changes the judgment criteria depending on the physical condition of the day. There is a problem of doing.
Further, since a considerably large inspection signal needs to be input in order to detect the chattering sound, there is a possibility that hearing loss may occur if the auditory perception is continuously performed for a long period of time.

Therefore, the present applicant previously invented a chattering sound detecting device capable of automatically and accurately detecting chattering sound of an electroacoustic transducer using a large-sized computer (Japanese Patent Application No. Hei 10 (1999) -135242). 2-290387). However, if a large computer is used, the whole apparatus becomes large-scale, and the installation location becomes a problem. In addition, it is very expensive, and there is a cost problem. Therefore,
It is unsuitable for use in actual inspections at various sites.

The object of the present invention is to detect the chattering sound of the electroacoustic transducer automatically, with high accuracy and at a practical processing speed, and to install the chattering sound easily and inexpensively. It is to provide a detection device.

[0007]

According to the present invention, a low-frequency swept sine wave is used for an electroacoustic transducer to be inspected by using a digital filter having characteristics most suitable for extracting the chattering sound component of the electroacoustic transducer. Wave signal is input, the output signal from the electroacoustic transducer is passed through the digital filter to extract the clinging sound component, and the extracted clinging sound component signal is arithmetically processed to produce the electroacoustic transducer to be inspected. Obtaining an evaluation value indicating the degree of stickiness, and determining the stickiness by comparing the obtained evaluation value with a predetermined reference value,
The present invention is capable of automatically and accurately determining a chattering sound in a short time by using a small-sized computer as low as a personal computer.

[0008]

According to the above construction, a considerably small chattering sound can be completely detected by a digital filter optimized in advance for the detection of chattering sound, so that a small size such as envelope processing or trend removal processing can be achieved. The computer does not need to perform time-consuming processing, and therefore the clinging sound can be automatically detected with high accuracy and in a short time. Further, since it is possible to perform processing using a small and inexpensive computer such as a personal computer, the entire apparatus can be made compact and inexpensive. further,
By changing the measurement algorithm as above,
1 for small computers, for example headphones
It is possible to inspect chattering noise at a sufficiently practical processing speed, such as a good / bad judgment time of 4 seconds.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration diagram showing an embodiment of a chattering sound detecting device according to the present invention, and shows a case where the present invention is applied to the detection of the chattering sound of small headphones. The signal source 11 generates a low-frequency swept sine wave signal of 50 Hz to 500 Hz at, for example, 20 mW under the control of an inexpensive small computer 12 such as a personal computer, and inputs it to the small headphones 13 which is an electroacoustic transducer to be inspected. The output acoustic signal from the small headphone 13 is received by the microphone 15 through the coupler 14. The analog electric signal output from the microphone 15 is amplified by the microphone amplifier 16 and then taken into the small computer 12.

The small computer 12 is an analog-digital converter (A / D) for converting an analog electric signal amplified by the microphone amplifier 16 into a digital signal.
17, and a digital filter 18 optimized in advance so that it is most easy to detect the chattering sound of small headphones,
The digital signal converted by the A / D 17 is passed through the digital filter 18 to extract the eccentricity component to calculate the evaluation value indicating the degree of the eccentricity, and the evaluation value is set to a predetermined reference value. It is provided with an arithmetic processing determination means 19 for making a pass / fail determination by comparing with.

The analog electric signal taken into the small computer 12 is converted into a digital signal by the A / D 17, and then inputted into the digital filter 18 to be digitally processed to extract a sticking component. As described above, the digital filter 18 is optimized so as to detect the chattering sound of the small headphones most easily, and therefore, even the faint chattering sound can be extracted.

The lazy component signal output from the digital filter 18 is input to the arithmetic processing determination means 19 and the autocorrelation function for each frame (predetermined time, for example, 2 milliseconds) is obtained. The maximum value of the autocorrelation function (autocorrelation coefficient) of these frames is taken, and an evaluation value indicating the degree of sticking of the headphones to be inspected is calculated from this maximum value. The evaluation value is compared with a predetermined reference value, and if the evaluation value is larger than the reference value, the headphone is determined to be defective and displayed on, for example, an appropriate display device (not shown).

The evaluation value, which is the boundary between the non-defective product and the defective product, is obtained in advance by a listening test of a large number of small headphones, and this is used as a reference value for the above determination. Further, as described above, the digital filter is optimized in advance so as to have a characteristic most suitable for extracting the chattering sound component of the small headphones. Since these are uniquely determined by the type of headphones and the inspection acceptance criteria, there is no problem at all.

In the case of detecting the chattering sound of the small headphones as in this embodiment, if the autocorrelation function of 20 frames is obtained when one frame is set to 2 milliseconds, the faint chattering sound can be completely detected. It was confirmed that it was possible. In addition, the digital filter is optimized to detect sticky noise most easily, so even if skipping the envelope processing and trend removal processing, which are time-consuming processes for small computers, the detection of sticky sound is affected. It was confirmed not to give. Therefore, the processing time can be shortened,
In the above configuration, the time required from the measurement of the rattling noise of one headphone to the determination was 4 seconds.

Next, analog filter processing (hereinafter simply referred to as analog processing) by a conventional chattering sound detecting device
With reference to FIGS. 2 to 4, description will be made on the results of detecting the chattering sound of the headphones by the digital filter processing (hereinafter, simply referred to as digital processing) by the chattering sound detecting apparatus according to the present invention. FIG. 2 shows the result of extracting a comparatively large clinging component.
Indicates the result extracted by conventional analog processing,
(B) shows the result extracted by digital processing according to the present invention. As is clear from the figure, when extracting a relatively loud chatter sound, similar results can be obtained by the conventional analog processing and the digital processing according to the present invention.

3A and 3B show the results obtained by extracting a comparatively small clinging component. FIG. 3A shows the results obtained by the conventional analog processing, and FIG. 3B shows the results obtained by the digital processing according to the present invention. The results are shown. As is clear from the figure, when extracting a comparatively small chattering sound, the chattering component is buried in noise in the conventional analog processing, and it is difficult to extract the chattering component. On the other hand, it can be seen that even the small clinging component is clearly extracted in the digital processing according to the present invention.

For this reason, as shown in FIG. 4, even in the case of a defective headphone in which a clinging sound is generated in the conventional analog processing, the rating value may be 0.0000. You cannot select only good products without sound. On the other hand, in the digital processing according to the present invention, a good product having no sticking noise and a defective product having sticking sound can be reliably separated with a constant evaluation value, so that only a good product having no sticking sound is based on the evaluation value. Can be accurately selected.

From the above results, the chattering sound detection apparatus according to the present invention is particularly effective in detecting a small chattering sound, which is difficult to judge by the conventional analog processing, and accurately detects the chattering sound. It turns out that sound can be detected. In the above embodiment, the case where the present invention is applied to the detection of the chattering sound of the small headphones has been described, but the present invention is not limited to the detection of the chattering sound of the small headphones. Needless to say, any electroacoustic transducer that can detect a sticking sound with the determination accuracy and the determination time that can be used for the inspection can be applied to other various electroacoustic transducers by simply changing the software. Further, in the above embodiment, the low frequency swept sine wave signal is generated from an independent signal source under the control of the small computer, but the low frequency swept sine wave signal may be generated in the small computer.
It goes without saying that various modifications and changes can be made as necessary.

[0019]

As described above, according to the present invention, since the digital filter pre-optimized for detecting the chattering sound is used, even the faint chattering sound of the electroacoustic transducer can be completely detected. Not only can you do this, you can eliminate the need for time-consuming processing with a small computer such as envelope processing and trend removal processing.
Moreover, there is a remarkable effect that the chattering sound of the electroacoustic transducer can be detected with the same degree of accuracy as when a large computer is used.

Further, since the processing can be performed using a small and inexpensive computer such as a personal computer, the entire apparatus can be constructed in a small size and at a low cost. Therefore, the apparatus can be installed in various sites and used as an electroacoustic transducer. There is also an effect that it becomes possible to perform an inspection of clinging sound.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a rattling sound detection device according to the present invention.

FIG. 2 shows a result of extracting a comparatively large vibration component of headphones by a conventional vibration noise detection device and a vibration noise detection device according to the present invention, and (A) shows an extraction result by the conventional detection device. FIG. 1B is a diagram showing the extraction result by the detection device according to the present invention.

FIG. 3 shows a result of extracting a comparatively small vibration component of headphones by a conventional vibration noise detection device and a vibration noise detection device according to the present invention, and (A) shows an extraction result by the conventional detection device. FIG. 1B is a diagram showing the extraction result by the detection device according to the present invention.

FIG. 4 shows the relationship between the evaluation value and the presence / absence of chattering noise in the conventional chattering noise detector and the chattering noise detector according to the present invention, and (A) shows the relationship in the conventional detector. B) is a diagram showing a relationship in the detection device according to the present invention.

[Explanation of symbols]

 11 signal source 12 small computer 13 small headphone 14 coupler 15 microphone 16 microphone amplifier 17 analog-digital converter 18 digital filter 19 arithmetic processing determination means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mamoru Yasuda 4-3-1 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture Inside the Research and Development Laboratory, Hosiden Corporation (72) Inventor Takashi Miyakura 4-Takazukadai, Nishi-ku, Kobe City, Hyogo Prefecture 3-1 Hosiden Corporation Development Technology Laboratory

Claims (3)

[Claims] 1. A signal generating means for generating a low frequency swept sine wave signal and inputting it to an inspected electroacoustic transducer, a microphone for receiving an output acoustic signal from the inspected electroacoustic transducer, and An analog-digital conversion means for converting an analog electric signal output from a microphone into a digital signal, a digital filter pre-optimized for detecting a sticking sound of the electroacoustic transducer to be inspected, and the digital signal as the digital signal. A calculation process for calculating the evaluation value indicating the degree of stickiness by calculating the stickiness component extracted by passing it through a filter, and comparing this evaluation value with a predetermined reference value to determine whether it is good or bad. A rattling sound detection device comprising: a determination unit. 2. The arithmetic processing determination means calculates an evaluation value indicating the degree of sticking of the electroacoustic transducer to be inspected from the maximum value of the autocorrelation function of the input sticking component,
The rattling noise detection device according to claim 1, wherein the evaluation value is compared with the predetermined reference value, and if the evaluation value is larger, it is determined as a defective product. 3. The electroacoustic transducer to be inspected is a small headphone, and the digital filter is optimized to most easily detect the chattering sound of the small headphone. 50Hz
The chattering sound detecting apparatus according to claim 1, wherein a sweeping sine wave signal of ˜500 Hz is input to automatically detect the presence or absence of the chattering sound of the small headphones.