JP2001330595A - Hammering test method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reliability of inspection by hammering, such as tightness inspection of a can product or the like. SOLUTION: A can 1 is hammered, and the exciting force is detected by a vibration detector 11, and the sound is detected by a microphone 3. The detected sound is separated into time series signals in each prescribed frequency band by each analog BPF 5, and each maximum value is recorded in each peak hold 7. The distance between the microphone 3 and the can 1 is obtained from the time difference measured by a time difference measuring apparatus 20, and a corrector 41 converts the maximum value recorded in each peak hold 7 into the maximum value in the reference distance. The ratio between the exciting forces at the reference value setting time and at the inspection time is operated by a ratio computing unit 15, and each converted maximum value is corrected again by the ratio by a corrector 8. A comparator 9 compares each corrected maximum value with the reference value, and emits a determination signal to an alarm unit 18. The maximum values in each band are extracted from the plural time series signals in each frequency band and compared, and corrected by the distance between the microphone 3 and the can 1, to thereby improve reliability of the inspection.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tapping sound inspection apparatus used for, for example, an airtight inspection of a can product, a bolt looseness inspection, and the like, and more particularly to a tapping sound inspection apparatus capable of improving the reliability of the inspection. is there.

[0002]

2. Description of the Related Art FIG.
FIG. 1 is a configuration diagram illustrating a conventional tapping sound inspection device disclosed in Japanese Patent Publication No. 0-205. In FIG. 8, 1 is a can as an object, 2 is a can 1
It is a hammer that strikes and generates a sound. Reference numeral 11 denotes a vibration sensor which is attached to the hammer 2 and converts acceleration of vibration of the can 1 into an electric signal.

An amplifier 12 amplifies the electric signal converted by the vibration sensor 11, and a rectifier 13 converts the signal amplified by the amplifier 12 into a direct current. Note that the signal obtained from the rectifier 13 is not a smoothed DC but a signal converted to one-way polarity, but is hereinafter referred to as DC for convenience.

Reference numeral 14 denotes a peak hold, and a rectifier 13
Holds the maximum peak value of the DC signal output from. 1
Reference numeral 5 denotes a ratio calculator for calculating the ratio between the output of the peak hold 14 and the peak reference value stored in the reference value setting device 16. Reference numeral 17 denotes a trigger detector which internally has a preset trigger reference value and issues a trigger signal based on a DC signal output from the rectifier 13.

Reference numeral 3 denotes a microphone, which is attached to the hammer 2 and detects vibration generated in the can 1 by impact as a sound wave and converts it into an electric signal. An amplifier 4 amplifies the electric signal converted by the microphone 3. Reference numeral 5 denotes an analog BPF (analog bandpass filter), which is configured by an analog circuit and has a narrow band characteristic, and separates a signal obtained from the amplifier 4 into an electric signal for each predetermined frequency band.

The analog BPF 5 is designed to cover, for example, a human audible range of about 20 to 20,000 Hz.
A total of 28 bands are provided for 9 octaves from 31.25 to 16,000 Hz to provide a resolution of 1/3 octave. 6 is a rectifier, analog B
The electric signal for each frequency band obtained from the PF 5 is rectified and converted to direct current.

Reference numeral 7 denotes a peak hold, which holds the maximum peak value of the output from the rectifier 6. 8 is a compensator,
The maximum peak value output from the peak hold 7 is corrected based on the ratio obtained from the ratio calculator 15, and a maximum peak value correction value is output. A comparator 9 compares the output of the corrector 8 with the reference value stored in the reference value setting device 10. 1
Reference numeral 8 denotes an alarm which outputs an alarm based on the comparison result from each of the plurality of comparators 9.

Next, the operation will be described. First, a reference value setting mode for setting each reference value using a reference target object will be described. The hammer 2 hits the can 1 as a reference object. At this time, the vibration generated in the hammer 2 is converted into an electric signal by the vibration sensor 11, and an appropriate gain is given by the amplifier 12. The amplified signal is supplied to a rectifier 13
To convert to DC.

The trigger detector 17 compares the DC signal from the rectifier 13 with a preset internal reference value, and outputs a trigger signal when the DC signal exceeds the reference value. The peak hold 14 records the maximum value of the DC signal input from the rectifier 13. At this time, the operation of the peak hold 14 is started by a trigger signal from the trigger detector 17.

The recording of such a maximum value is performed for a certain period of time until the sound pressure generated by the impact on the object is attenuated to some extent, and thereafter the output from the peak hold 14 is stored in the reference value setting unit 16 as a peak reference value. .

Similarly, the sound wave generated in the can 1 by the impact is converted into an electric signal by the microphone 3, and an appropriate gain is given by the amplifier 4. The amplified sound pressure signal is input to an analog BPF 5 provided in plural numbers and set to pass components of different frequency bands, and separated into time-series signals for each frequency band.

The time series signal separated for each frequency band by the analog BPF 5 is converted into a DC signal by a rectifier 6 and input to a peak hold 7. The peak hold 7 starts the recording operation of the maximum value of the DC signal from the rectifier 6 in response to the trigger signal from the trigger detector 17, and the sound pressure of the object attenuates to a predetermined value or less as in the case of the vibration peak hold 14. It takes place for a certain period of time. In this way, the instantaneous maximum value for each frequency band is recorded.

After a certain time elapses until the sound pressure attenuates to some extent, the maximum value recorded by the peak hold 7 is stored in each reference value setting device 10 as a reference value. By the operation of the reference value setting mode, the reference value setting device 16 stores the maximum value of the value corresponding to the acceleration of the vibration generated in the hammer 2 which is the information indicating the impact strength as a reference value,
The reference value setting unit 10 stores, as a reference value, a maximum value of a value corresponding to the sound pressure captured by the microphone 3, which is information indicating the instantaneous maximum sound pressure in each frequency band of the tapping sound.

Next, an inspection mode for inspecting an object will be described. First, the can 1 as an object is hit with the hammer 2. At this time, as in the reference value setting mode,
The vibration generated in the hammer 2 is converted into an electric signal by the vibration sensor 11, amplified by the amplifier 12, and converted into a direct current by the rectifier 13. Similarly, the trigger detector 17 also performs a trigger output from the DC signal from the rectifier 13 and
Reference numeral 4 records the maximum value of the DC signal within a certain period of time from the trigger output until the sound pressure attenuates to some extent.

In the test mode, the maximum value recorded in the peak hold 14 is input to the ratio calculator 15 after a certain period of time until the sound pressure attenuates to some extent.
Is the maximum value from the peak hold 14 and the reference value setting device 1
6 to calculate and output the ratio with respect to the peak reference value.

The sound wave generated by the impact is also converted into an electric signal by the microphone 3 and amplified by the amplifier 4 as in the reference value setting mode. The amplified electric signal is separated into a time series signal for each frequency band by the analog BPF 5, converted into a DC signal by the rectifier 6, and then input to the peak hold 7. The peak hold 7 records the maximum value of the DC signal for a certain period of time until the sound pressure after the trigger signal is output from the trigger detector 17 decreases to some extent.

In the test mode, the maximum value recorded in the peak hold 7 is input to the compensator 8 after a certain time elapses until the sound pressure attenuates to some extent.
An appropriate correction value is calculated based on the ratio obtained from 5 and the maximum value obtained from the peak hold 7 is corrected and output.

At this time, assuming that the generated sound pressure level is to be corrected, for example, in proportion to the applied external force, that is, the exciting force, a ratio twice as large as the reference value is calculated by the ratio calculator 1.
If obtained at 5, the maximum value recorded in peak hold 7 is divided by 2. In other words, if the exciting force in the inspection mode is twice as large as the exciting force in the reference value setting mode, the sound pressure level at each frequency generated is also assumed to be doubled. The obtained maximum value is divided by 2 so as to be converted into the excitation force in the reference value setting mode.

The maximum value corrected in this manner is compared with the reference value stored in the reference value setting device 10 by the comparator 9, and when the relation deviates from a predetermined relationship set in advance, an alarm signal is output. 18 is output. As the predetermined relationship at this time, for example, a range of 80 to 120% with respect to the reference value is set as normal, and a range of less than 80% and more than 120% as abnormal.

If the reference value is smaller than the overall sound pressure level, the lower limit side is canceled and an alarm signal is issued only when the reference value exceeds 120%. Prevent false alarms in band.

An alarm signal from the comparator 9 in each frequency band is input to the alarm device 18, and when the number of alarm signals exceeds a preset number, for example, two, an alarm is issued to the outside as an abnormality.

[0022]

The conventional tapping sound inspection apparatus has the following problems since it is configured as described above. (1) The microphone that detects the sound detects even the vibration of the hammer, and the true striking sound cannot be accurately detected. (2) Since the microphone is attached to a hammer that applies a vibrating force, it becomes an obstacle when hitting. (3) In addition, if the microphone is removed from the hammer and the sound is detected, the distance between the microphone and the target object is likely to change each time the ball is hit, so that it is difficult to ensure the reproducibility of the detected sound. Reliability may be reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to obtain a hammering sound inspection apparatus capable of improving the reliability of the inspection.

[0024]

In order to achieve the above object, a hitting sound inspection apparatus according to the present invention comprises a signal detection device for detecting, as a detection signal, a sound generated from an object to which external force is applied by external force applying means. Means, external force detecting means for detecting the magnitude of the external force applied by the external force applying means, time measuring means for measuring the time from detection of the external force to detection of a detection signal, and a plurality of predetermined times for detecting the detection signal. Conversion means for converting the time series signal into time series signals for each frequency band; extraction means for extracting the maximum value of the time series signal for each frequency band; comparison means for comparing each maximum value with a preset reference value; And a correction means for correcting at least one of each detection signal, time-series signal, maximum value, and reference value according to the magnitude of the detection signal and the time. The detection signal is converted into a time-series signal for each of a plurality of frequency bands, and the maximum value in each of the time-series signals is extracted. Therefore, the frequency resolution of the detection signal is improved, and the maximum value is detected with high sensitivity from the time-series signal. Can be extracted. Therefore, the characteristics of the loud sounds immediately after generation, which are also the characteristics of the striking sounds, can be accurately grasped and compared. In addition, the correction is made according to the magnitude of the external force to prevent the influence of the variation in the magnitude of the external force applied in the comparison by the comparing means. For example, by performing different corrections according to the external force for each frequency band, it is possible to compare with high reliability even an object having a complicated structure in which the distribution of frequency components changes according to the applied external force.
Furthermore, the time from the detection of the external force to the detection of the detection signal is measured to determine the distance from the object to the signal detection means from the speed of the sound, and the distance between the object and the signal detection means is in the reference state. Since the comparison is made after correcting to the current state, the comparison can be performed without being affected by the distance between the signal detection means and the object.

The signal detecting means detects a sound generated from the object to which the external force is applied by the external force applying means as a detection signal, and the external force applying means attenuates the transmission of the vibration from the external force applying means to a predetermined value or less. External force detecting means for detecting the magnitude of the external force fixed as described above, converting means for converting the detection signal into a time series signal for each of a plurality of predetermined frequency bands, and extracting the maximum value of the time series signal for each frequency band Extracting means, comparing means for comparing each maximum value with a preset reference value, and correcting at least one of each detection signal, time-series signal, maximum value, and reference value according to the magnitude of the external force. Correction means. When the signal detecting means is fixed to the external force applying means so as to attenuate the transmission of vibration from the external force applying means to a predetermined value or less, and the measurement is performed, the distance between the object and the signal detecting means is substantially constant at each inspection. And an error due to transmission of sound from the external force applying means to the signal detecting means can be prevented.

Further, signal detection means for detecting, as a detection signal, a sound generated from the object to which the external force is applied by the external force application means, and detection signal maximum value detection means for detecting the maximum value of the detection signal as the detection signal maximum value. Converting means for converting a detection signal into a time series signal for each of a plurality of predetermined frequency bands; extracting means for extracting a maximum value of the time series signal for each frequency band; and a time series signal based on the detection signal maximum value. And a comparing means for comparing each detected signal maximum value ratio with a preset reference value. . If the ratio of the maximum value of the time-series signal to the maximum ratio of the detection signal is determined based on the maximum value of the detection signal, the comparison can be performed without being affected by the strength of the excitation force or the magnitude of the detection signal.

Signal detecting means for detecting, as a detection signal, a sound generated from an object to which an external force is applied by the external force applying means, and converting means for converting the detection signal into a time series signal for each of a plurality of predetermined frequency bands. Extracting means for extracting the maximum value of the time-series signal for each frequency band, frequency band maximum value detecting means for detecting the largest value of the maximum values of the time-series signal as the frequency band maximum value, and frequency band maximum value Means for calculating the ratio of the maximum value of each time-series signal as the ratio of the maximum value to the frequency band with reference to the frequency band maximum value ratio calculating means, and comparing means for comparing each of the frequency band maximum value ratios with a preset reference value It is provided with. If the ratio of the maximum value of each time-series signal to the frequency band maximum value ratio is determined based on the frequency band maximum value, the comparison can be performed without being affected by the strength of the excitation force or the size of the detection signal. .

Signal detecting means for detecting, as a detection signal, a sound generated from the object to which the external force is applied by the external force applying means; and converting means for converting the detection signal into a time series signal for each of a plurality of predetermined frequency bands. Extraction means for extracting the maximum value of the time-series signal for each frequency band, and the maximum value of the time-series signal after a predetermined time has elapsed since the application of the external force after the predetermined time has elapsed for each frequency band. The maximum value extracting means after a lapse of a predetermined time to extract as a value, the attenuation rate calculating means for obtaining a ratio of the maximum value after a lapse of a predetermined time as an attenuation rate based on the maximum value of the time-series signal, and each attenuation rate is preset. And a comparing means for comparing with a reference value. If the ratio of the maximum value after a lapse of a predetermined time is determined as the attenuation rate with reference to the maximum value of the time-series signal, the comparison can be performed without being affected by the strength of the excitation force or the magnitude of the detection signal.

Further, signal detecting means for detecting, as a detection signal, a sound generated from the object to which the external force is applied by the external force applying means, and converting means for converting the detection signal into a time series signal for each of a plurality of predetermined frequency bands. Extracting means for extracting the maximum value of the time-series signal for each frequency band; effective value calculating means for calculating the effective value of the time-series signal; and an effective value of the time-series signal based on the maximum value of the time-series signal. It is provided with time measuring means for measuring the decay time until the ratio reaches a predetermined value, and comparing means for comparing each decay time with a preset reference value. By measuring the decay time until the ratio of the effective value of the time-series signal reaches a predetermined value based on the maximum value of the time-series signal and comparing with the reference value, the magnitude of the excitation force and the magnitude of the detection signal can be determined. Comparisons can be made without being affected.

The comparing means sets a range of the reference value based on a plurality of detection signals obtained when the object is in a predetermined state, and the range of the reference value deviates from the predetermined range. 7. The method according to claim 1, further comprising a comparison result exclusion unit for excluding a comparison result of the comparison unit of the frequency band. When the variation of the sound generated from the object is large, the setting range of the set reference value is wide, but when the range is too wide, it can be considered as a noise component generated from outside the object, and is adopted as the reference value. Is inappropriate, the comparison result of the comparator in the frequency band is excluded from the determination target.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a configuration diagram showing the configuration of the hammering inspection device. In FIG. 1, 1
Reference numeral denotes a can as an object, and reference numeral 2 denotes a hammer which strikes the can 1 to generate a hitting sound. Reference numeral 11 denotes a vibration sensor which is attached to the hammer 2 and converts acceleration of vibration of the can 1 into an electric signal.

An amplifier 12 amplifies the electric signal converted by the vibration sensor 11, and a rectifier 13 converts the signal amplified by the amplifier 12 into a direct current. Note that the signal obtained from the rectifier 13 is not a smoothed DC but a signal converted to one-way polarity, but is hereinafter referred to as DC for convenience.

Reference numeral 14 denotes a peak hold, and the rectifier 13
Holds the maximum peak value of the DC signal output from. 1
Reference numeral 5 denotes a ratio calculator for calculating the ratio between the output of the peak hold 14 and the peak reference value stored in the reference value setting device 16. Reference numeral 17 denotes a trigger detector, which internally has a preset trigger reference value, and issues a trigger signal when the DC signal output from the rectifier 13 exceeds the trigger reference value.

Reference numeral 3 denotes a microphone, which is attached to the hammer 2 and detects a vibration generated in the can 1 by a blow as a sound wave and converts it into an electric signal. An amplifier 4 amplifies the electric signal converted by the microphone 3. Reference numeral 5 denotes an analog BPF (analog bandpass filter), which is configured by an analog circuit and has a narrow band characteristic, and separates a signal obtained from the amplifier 4 into an electric signal for each predetermined frequency band.

This analog BPF 5 covers, for example, almost 20 to 20,000 Hz which is a human audible range.
A total of 28 bands are provided for 9 octaves from 31.25 to 16,000 Hz to provide a resolution of 1/3 octave. 6 is a rectifier, analog B
The electric signal for each frequency band obtained from the PF 5 is rectified and converted to direct current.

Reference numeral 7 denotes a peak hold, which records the maximum peak value of the output from the rectifier 6. 8 is a compensator,
The maximum peak value output from the peak hold 7 is corrected based on the ratio obtained from the ratio calculator 15, and a maximum peak value correction value is output. A comparator 9 compares the output of the corrector 8 with the reference value stored in the reference value setting device 10. 1
Reference numeral 8 denotes an alarm which outputs an alarm based on the comparison result from each of the plurality of comparators 9.

Reference numeral 20 denotes a time difference measuring device for measuring a time difference between the trigger signal of the trigger detector 17 and the trigger signal of the trigger detector 32. A rectifier 31 rectifies the output of the amplifier 4 without passing through the analog BPF 5. A trigger detector 32 generates a trigger signal when the output of the rectifier 31 exceeds a predetermined value. Reference numeral 41 denotes a corrector, and a peak hold 7 based on the time measured by the time difference measuring device 20.
Correct the maximum peak value recorded by.

Next, the operation will be described. First, a reference value setting mode for setting each reference value using a reference target object will be described. The hammer 2 hits the can 1 as a reference object. At this time, the vibration generated in the hammer 2 is converted into an electric signal by the vibration sensor
Gives an appropriate gain. This amplified signal is converted to a rectifier 1
In step 3, it is converted to DC.

The trigger detector 17 compares the DC signal from the rectifier 13 with a preset internal reference value, and outputs a trigger signal when the DC signal exceeds the reference value. The peak hold 14 records the maximum value of the DC signal input from the rectifier 13. At this time, the operation of the peak hold 14 is started by a trigger signal from the trigger detector 17 in order to prevent the operation from being erroneously started due to noise or the like.

The recording of such a maximum value is carried out for a certain period of time until the sound pressure generated by the impact on the object is attenuated to a certain extent, and thereafter, the maximum value peak value recorded in the peak hold 14 is set as a reference value. Is stored in the container 16.

Similarly, the sound wave generated in the can 1 by the impact is converted into an electric signal by the microphone 3, and an appropriate gain is given by the amplifier 4. The amplified sound pressure signal is input to an analog BPF 5 provided in plural numbers and set to pass components of different frequency bands, and separated into time-series signals for each frequency band.

The time-series signal separated for each frequency band by the analog BPF 5 is converted into a DC signal by the rectifier 6 and input to the peak hold 7. The peak hold 7 starts the recording operation of the maximum value of the DC signal from the rectifier 6 in response to a trigger signal from the trigger detector 7, and the sound pressure of the object attenuates to a predetermined value or less, similarly to the vibration peak hold 14. It takes place for a certain period of time. In this way, the instantaneous maximum value for each frequency band is recorded.

After a certain time elapses until the sound pressure attenuates to some extent, the maximum value recorded by the peak hold 7 is stored in each reference value setting device 10 as a reference value.

At the same time, the rectifier 31 and the trigger detector 32 detect the trigger of the vibration from the microphone 3 amplified by the amplifier 4 without passing through the analog BPF.
The time difference measuring device 20 calculates a time difference between the trigger signal of the trigger detector 17 due to the vibration detected by the vibration sensor 11 and the trigger signal of the trigger detector 32 due to the vibration detected by the microphone 3.

The compensator 41 obtains the distance between the microphone 3 and the can 1 as an object from the time difference and the sound speed. The sound pressure at the microphone 3 is
Assuming that it is inversely proportional to the square of the distance between the microphone 3 and the can 1, the maximum value recorded in the peak hold 7 is corrected so as to convert the reference distance between the microphone 3 and the can 1 into a reference, for example, 30 cm.

That is, if the distance obtained from the time difference is 60
cm, the sound pressure is assumed to be proportional to the square of the distance. In order to convert to the case of the reference distance of 30 cm, the maximum value recorded in the peak hold 7 is corrected to a value quadrupled, and the reference value is set. It is stored in the device 10 as a maximum value serving as a reference. The distance between the microphone 3 and the can 1, which is the object, can be freely selected by such correction. However, due to the nature of the reference value setting mode, the distance is preferably set to a value as close as possible to the reference distance (for example, 30 cm). It is desirable.

By the operation of the reference value setting mode, the reference value setting device 16 stores the maximum value of the value corresponding to the acceleration of the vibration generated in the hammer 2 as the reference value, which is information indicating the strength of the impact. The reference value setting unit 10 stores, as a reference value, the maximum value of the value corresponding to the sound pressure captured by the microphone 3, which is information indicating the instantaneous maximum sound pressure in each frequency band of the tapping sound.

Next, an inspection mode for inspecting an object will be described. First, the can 1 as an object is hit with the hammer 2. At this time, as in the reference value setting mode,
The vibration generated in the hammer 2 is converted into an electric signal by the vibration sensor 11, amplified by the amplifier 12, and converted into a direct current by the rectifier 13.

The trigger detector 17 similarly outputs a trigger from the DC signal from the rectifier 13 and
Records the maximum value of the DC signal within a certain time from when the trigger signal is output from the trigger detector 17 until the sound pressure attenuates to some extent.

In the case of the inspection mode, the maximum value recorded in the peak hold 14 is input to the ratio calculator 15 after a certain time elapses until the sound pressure attenuates to some extent.
Is the maximum value from the peak hold 14 and the reference value setting device 1
6 to calculate and output the ratio with respect to the peak reference value.

The sound wave generated by the impact is also converted into an electric signal by the microphone 3 and amplified by the amplifier 4 as in the reference value setting mode. The amplified electric signal is separated into a time series signal for each frequency band by the analog BPF 5, converted into a DC signal by the rectifier 6, and then input to the peak hold 7.

The peak hold 7 records the maximum value of the DC signal for a certain period of time until the sound pressure from the trigger output attenuates to some extent. In the case of the inspection mode, the maximum value recorded in the peak hold 7 is input to the corrector 41 after a lapse of a predetermined time until the sound pressure attenuates to some extent.

The time difference measuring device 20 obtains a time difference between the trigger signal of the trigger detector 17 due to the vibration detected by the vibration sensor 11 and the trigger signal of the trigger detector 32 due to the vibration detected by the microphone 3. The corrector 41 obtains the distance between the microphone 3 and the can 1 from the time difference by converting it from the speed of sound, corrects the maximum value recorded in the peak hold 7, and outputs the corrected value to the corrector 8.

The correction based on the time difference by the corrector 41 is as follows.
For example, the distance between the can 1 and the microphone 3 is the reference distance 30c.
m and the time difference at this time is 0.8 ms, the time difference becomes 1.6 at a distance of 60 cm.
ms. If you compare this time, it is twice, so
The maximum value recorded in the peak hold 7 is multiplied by 4 which is twice the square. That is, since the distance is 60 cm, which is twice the reference distance of 30 cm, the detected sound pressure is:
Assuming that it is the square of (1/2), the obtained maximum value is multiplied by four so as to be converted into the sound pressure at the reference distance of 30 cm in the reference value setting mode.

The corrector 8 calculates an appropriate correction value based on the ratio obtained from the ratio calculator 15, and further corrects the corrected maximum value obtained from the corrector 41 with this correction value. Output to When the correction by the corrector 8 is performed, for example, assuming that the generated sound pressure level is proportional to the applied external force, that is, the exciting force, the correction is performed by 2 to the reference value.
When the double ratio is obtained by the ratio calculator 15, the maximum value recorded in the peak hold 7 is multiplied by (1/2). In other words, if the exciting force in the inspection mode is twice as large as the exciting force in the reference value setting mode, the sound pressure level at each frequency generated is also assumed to be doubled. The maximum value is multiplied by (1/2) so as to be converted into the excitation force in the reference value setting mode.

Accordingly, the compensator 41 multiplies the maximum value recorded in the peak hold 7 by four times with respect to the distance between the microphone 3 and the can 1, and the compensator 8 operates in the reference value setting mode obtained by the ratio calculator 15. Since the current excitation force is twice as large as the excitation force at
2) multiply and eventually multiply the maximum value recorded in the peak hold 7 by 4 × (１ ／) = 2, and output the corrected maximum value to the comparator 9.

The maximum value corrected in this way is compared by the comparator 9 with the reference value stored in the reference value setting device 10, and when the relationship deviates from a predetermined relationship, an alarm signal is output.
8 is output. The predetermined relationship is, for example, normal within a range of 80 to 120% with respect to a reference value, less than 80%, and 12%.
Above 0% is set as abnormal. In other words, 80 to 120% of the obtained reference value is used as a determination criterion, and the comparator 9 determines that there is an abnormality when it is out of this range, and issues a signal.

If the reference value is smaller than the overall sound pressure level, the lower limit side is released and an alarm signal is issued only when the reference value exceeds 120%. Prevent false alarms in band.

The alarm signal from the comparator 9 in each frequency band is input to the alarm device 18, and when the alarm signal exceeds a preset number, for example, two, an alarm is issued to the outside as an abnormality.

As described above, the time difference due to the generated sound is detected, the distance between the microphone 3 and the can 1 to be inspected is obtained, and the signal detected by the microphone 3 is corrected. The microphone 3 can be installed in a position where the microphone 3 is not received.

Although the sound pressure of the tapping sound detected by the microphone 3 changes depending on the distance between the microphone 3 and the can 1, the inspection can be performed without being affected by the change in the sound pressure. The reliability of inspection can be improved.

Embodiment 2 FIG. 2 is a configuration diagram of a tapping sound inspection apparatus according to another embodiment of the present invention. In FIG. 2, reference numeral 33 denotes a microphone, which is attached to the back of the hand of the person holding the hammer 2 using a fixing means such as a glove 34 having a holding device for the microphone 33.
Other configurations are the same as those of the conventional hitting sound inspection device shown in FIG. 8, and the corresponding components are denoted by the same reference numerals and description thereof will be omitted.

Next, the operation will be described. Here, the microphone 33 is fixed to the hammer 2 of the vibration source via a human hand. First, can 1 by hammer 2
To blow. At this time, the sound wave generated by the impact is converted into an electric signal by the microphone 33.

However, at this time, vibration is generated in the hammer 2 by hitting, and the vibration is transmitted to the microphone 33. Here, the microphone 33 is not directly fixed to the hammer 2 but is fixed to the back of the hand opposite to the palm through the hand of a person. Therefore, the human hand becomes a cushioning material, and the vibration generated by the hammer 2 is attenuated and hardly transmitted to the microphone 33.

As described above, the microphone 33 is attached to the glove 34.
, And indirectly fixed to the hammer 2 via a human hand, the transmission of vibration of the hammer 2 can be prevented, and the distance between the microphone 33 and the can 1 as an object can be prevented. Can be kept substantially constant each time the inspection is performed, and the reliability of the inspection can be improved.

Instead of fixing the microphone to the hammer via human hands, the microphone is fixed to the hammer via an elastic member such as rubber having a large elasticity so as to prevent transmission of vibration from the hammer. Is also good.

Embodiment 3 FIG. 3 is a configuration diagram of a tapping sound inspection apparatus according to still another embodiment of the present invention. In FIG. 3, 21 is a ratio calculator, and 36 is a peak hold. The electric signal of the sound from the microphone 3 is input from the amplifier 4 to the rectifier 31 without passing through the analog BPF 5, and the maximum value is recorded in the peak hold 36.

The maximum value C recorded in the peak hold 36
And the maximum value D of the vibration output from the peak hold 7 for each frequency band are input to the ratio calculator 21 and the ratio R = C / D is calculated. The calculated ratio R is input to the reference value setting device 10 or the comparator 9. Other configurations are the same as those of the first embodiment shown in FIG. 1, and the corresponding components are denoted by the same reference numerals and description thereof is omitted.

Next, the operation will be described. In the reference value setting mode, a tapping sound generated by hitting the standard can 1 with the hammer 2 is input to the peak hold 36 via the rectifier 31 without passing through the analog BPF, and its maximum value C0 is obtained. . The maximum value C is input to the ratio calculator 21. Further, the maximum value D0 of the peak hold 7 obtained through each analog BPF 5 is input to each ratio calculator 21. The ratio calculator 21 calculates the maximum value C0 and the maximum value D
A ratio R0 = C0 / D0 with respect to 0 is obtained, and the reference value setting unit 10
As a reference value.

In the inspection mode, the hammer 2 hits the can 1 which is the object to be inspected,
1 to the peak hold 36 and its maximum value C
Find 1 The maximum value C is input to the ratio calculator 21. The maximum value D1 of the peak hold 7 obtained through each analog BPF 5 is input to each ratio calculator 21. The ratio calculator 21 calculates the maximum value C1 and the maximum value D
A ratio R1 = C1 / D1 with 1 is obtained and output to the comparator 9.

The ratio R1 is compared with the reference value R0 stored in the reference value setting device 10 in the comparator 9, and an alarm signal is output to the alarm device 18 when the ratio deviates from a predetermined relationship set in advance. . The predetermined relationship at this time is
For example, a value within the range of 80 to 120% of the reference value is normal,
Less than 80% and more than 120% are set as abnormal.

The ratio R1 thus obtained is obtained by dividing the maximum value C1 of the vibration signal obtained for each frequency band through each analog BPF 5 by the maximum value D1 of the original signal obtained without passing through the analog BPF. And normalized.

As described above, in the comparator 9, the judgment is made using the normalized maximum value, so that the inspection can be performed without being affected by the strength of the strike and the position of the microphone. The operability of the sound inspection device and the reliability of the inspection can be improved.

Embodiment 4 FIG. 4 is a configuration diagram of a tapping sound inspection apparatus according to another embodiment of the present invention. In FIG. 4, reference numeral 22 denotes a maximum value extractor. The maximum value is input from each peak hold 7 after passing through each analog BPF 5, and the maximum value is further extracted from the maximum value to calculate a ratio. Output to the container 21. Each ratio calculator 2
1 calculates the ratio of the maximum value recorded in each peak hold 7 to the maximum value extracted by the maximum value extractor 22, and outputs the ratio to the comparator 9.

The other configuration is the same as that of the third embodiment shown in FIG. 3, and the corresponding components are denoted by the same reference numerals and description thereof is omitted.

Next, the operation will be described. The hitting sound generated by hitting the can 1 with the hammer 2 is the analog BPF
5. The signal is decomposed by the peak hold 7 into a maximum value for each frequency band. The maximum value for each frequency band is compared by the maximum value extractor 22, and the maximum value is extracted. The ratio calculator 21 sets the maximum value extracted by the maximum value extractor 22 as 100%, and calculates the percentage of the maximum value recorded in the peak hold 7 for each frequency band.

In the reference value setting mode, the maximum value extractor 22
The ratio is calculated by the ratio calculator 21 using the maximum value as the denominator and the numerator as the numerator using the maximum value recorded in the peak hold 7 for each frequency band. Is stored.

The hitting sound detected in this way is analog B
The maximum value of each component obtained by decomposing for each frequency band by the PF5 is normalized by the maximum value among the components, and then compared by the comparator 9 to determine the strength of the impact and the microphone and the object. The error due to the distance from the distance is eliminated, and the reliability of the inspection can be improved.

Embodiment 5 FIG. FIG. 5 is a configuration diagram of a tapping sound inspection device according to still another embodiment of the present invention. In FIG. 5, 23 is a timer, and 37 is another peak hold. The timer 23 measures the time since the trigger detector 17 outputs the trigger signal, and issues a signal to another peak hold 37 when a predetermined time has elapsed. Other configurations are the same as those of the third embodiment shown in FIG. 3, and the corresponding components are denoted by the same reference numerals and description thereof is omitted.

Next, the operation will be described. For example, when a casting is hit with a hammer 2 as an inspection target, the lingering sound remains for a long time in a normal product, but the lingering sound is attenuated in a short time if a crack is formed. The hammering sound inspection apparatus according to the present embodiment decomposes the hammering sound when hit with the hammer 2 for each frequency band with each analog BPF 5 and records the maximum value F of each component immediately after the hitting with the peak hold 7. I do.

The timer 23 detects the trigger detector 1 immediately after the impact.
The time counting is started with the trigger signal of No. 7 as a trigger. Then, after a lapse of a predetermined time, the maximum value G of the hitting sound thereafter is recorded by another peak hold 37.
The ratio calculator 21 obtains a ratio S = G / F between the maximum value G of the hitting sound recorded after a lapse of a predetermined time and the maximum value F of the hitting sound recorded immediately after the hit, and sets the ratio S and the reference value setting. The reference value set in the device 10 is compared with the reference value by the comparator 9 to make a determination.

In the reference value setting mode, for example, when a normal casting is hit, the maximum value of the hitting sound recorded immediately after the hit of the peak hold 7 in a certain frequency band is F1.
If the maximum value G1 of the hitting sound recorded after 3 seconds is 80% based on the maximum value F1, the ratio arithmetic operation unit 21 calculates the ratio S1 = 0.8.
The ratio 0.8 is stored in the reference value setting device 10 as a reference value. The same applies to the reference values of the reference value setting device 10 in other frequency bands.

Next, in the inspection mode, the casting to be inspected is hit and the maximum value of the hitting sound recorded immediately after the hitting is F
A ratio S2 between the maximum value G2 of the hitting sound recorded after 2 and 3 seconds is obtained by a ratio calculator 21, and the ratio S2 is compared with a reference value 0.8 set in the reference value setting device 10 in a comparator 9. And outputs an alarm signal to the alarm device 18 when the relationship deviates from a predetermined relationship set in advance.

Since the attenuation rate is hardly affected by the strength of the tapping sound, the determination based on the attenuation rate of the tapping sound over time eliminates errors due to the strength of the tapping sound, and the reliability of the test is reduced. Can be improved.

Embodiment 6 FIG. FIG. 6 is a configuration diagram of a tapping sound inspection apparatus according to another embodiment of the present invention. In FIG. 6, 24 is a ratio comparator, 25 is a time measurement device, and 3 is a time measurement device.
8 is an effective value calculator. The electric signal of the microphone 3 rectified by the rectifier 6 is input to an effective value calculator 38, where the effective value is calculated and output to the ratio comparator 24.
The time measuring device 25 measures time based on a trigger signal from the trigger detector 17 and a signal from the ratio comparator 24.

Next, the operation will be described. The hitting sound generated by hitting the can 1 with the hammer 2 is output to each analog BPF.
5. After being decomposed into components for each frequency band by the peak hold 7, the maximum value F of each component immediately after the impact is recorded in the peak hold 7.

At the same time, the time measuring device 25 starts time measurement using the trigger signal of the trigger detector 17 as a trigger immediately after the impact. Although the output from each analog BPF 5 attenuates with the passage of time, the ratio comparator 24 sets the effective value calculator 38 based on the maximum value recorded in the peak hold 7.
When the effective value calculated in step (1) attenuates below a predetermined value, a signal is sent to the time measuring device 25.

When the time measuring device 25 receives the signal from the ratio comparator 24, the time measuring device 25 stops measuring the time. The comparator 9 compares the time measured by the time measuring device 25 with the reference time set in the reference value setting device 10, and issues an alarm signal when the relationship deviates from a predetermined relationship set in advance. Container 18
Output to

In the reference value setting mode, when a normal inspection object is hit, the maximum value recorded in the peak hold 7 in a certain frequency band is F3, while the maximum value is calculated by the effective value calculator 38. The maximum value for each frequency band is H
Assume that Then, the ratio U =
F3 / H is calculated, the time until the ratio U decreases to a predetermined value is measured by the time measuring device 25, and this time is set in the reference value setting device 10 as a reference value. The same applies to the reference values of the reference value setting device 10 in other frequency bands.

The error due to the strength of the percussion sound is determined by making a determination based on the time until the attenuation rate of the frequency band component included in the percussion sound detected in this manner over time becomes equal to or less than a predetermined value. And the reliability of the inspection can be improved.

Embodiment 7 FIG. FIG. 7 is a configuration diagram of a tapping sound inspection device according to still another embodiment of the present invention. In FIG. 7, 27 is a reference value setting device, and 28 is a setting value width comparator. The reference value setting unit 27 stores the maximum value of the peak hold 7 corrected by the corrector 8 as a reference value in the reference value setting mode. The setting value width comparator 28 outputs a signal that excludes the determination result based on the reference value depending on the value of the reference value of the reference value setting device 10 set in the reference value setting mode, as described in detail later. Call 9

Next, the operation will be described. In the reference value setting mode, for example, the reference can 1 is hit with the hammer 2, the maximum value recorded in the peak hold 7 is corrected by the corrector 8, and the corrected value is stored in the reference value setter 27. This maximum value is stored by hitting a predetermined number of cans as a reference each predetermined number of times, obtaining a predetermined number of maximum values, and storing the minimum value and the maximum value of the maximum value at this time. The range of the variation of the maximum value is set as the range of the reference value of the reference value setting unit 27. It should be noted that the variation in the striking force in the case of striking a plurality of times does not affect the setting of the reference value because it is corrected by the corrector 8.

When the variation of the hitting sound generated from the object is large, the range of the reference value set in the reference setting mode is widened. That is, in the case of an inspection object having a large variation in generated tapping sound, the range of the reference value for determination, that is, the range of determination as normal must be widened. However, if the range of the reference value exceeds a certain range, it is inappropriate to adopt it as the reference value, and the determination result of the frequency band should be excluded.

That is, it can be considered as a noise component other than the object, not the frequency indicating the characteristic of the object generated from the impact. Therefore, the set value width comparator 28 determines whether the range of the value stored as the reference value in the reference value set device 27 in the reference value setting mode is larger than a predetermined range. Is determined to have large noise, and the comparison result is excluded from the determination target.

For example, in the reference value setting mode, the reference value set in the reference value setting device 27 of a certain frequency band is 6
Suppose that it was 0 to 200%. Since the range of the reference value is too large, the set value width comparator 28 issues a signal not to output the determination result of the comparator 9 in the frequency band to the alarm device 18. Thereby, erroneous determination due to noise can be prevented, and the reliability of the inspection can be improved.

By appropriately combining the above-described embodiments, it is possible to further improve the operability of the hammering sound inspection apparatus and the reliability of the inspection. For example, in place of the reference value setting device 10 in the embodiment of FIG. 1, the reference value setting device 27 of FIG. 7 is used to determine a range of the variation from data by a plurality of hits in the reference value setting mode. It can be set as a reference value.

Further, the reference value may not be set in the reference value setting mode, and data of the inspection object obtained in advance may be used, or an average value M and a standard deviation σ may be obtained from a plurality of data. For example, (M−3σ) to (M + σ)
May be used as the reference value for.

[0098]

Since the present invention is constructed as described above, it has the following effects.

Signal detection means for detecting, as a detection signal, a sound generated from the object to which the external force is applied by the external force application means, external force detection means for detecting the magnitude of the external force applied by the external force application means, Time measurement means for measuring the time from detection to detection of a detection signal, conversion means for converting the detection signal into a time series signal for each of a plurality of predetermined frequency bands, and a frequency band Extracting means for extracting each time, a comparing means for comparing each maximum value with a preset reference value, and a detection signal, a time series signal, a maximum value, and a reference value according to the magnitude of the external force and the time. And a correction means for correcting at least one of the signals. The detection signal is converted into a time series signal for each of a plurality of frequency bands, and the maximum value in each of the time series signals is extracted. With frequency resolution is improved,
The maximum value can be extracted from the time-series signal with high sensitivity. Therefore, the characteristics of the loud sounds immediately after generation, which are also the characteristics of the striking sounds, can be accurately grasped and compared. In addition, the correction is made according to the magnitude of the external force to prevent the influence of the variation in the magnitude of the external force applied in the comparison by the comparing means. For example, by performing different corrections according to the external force for each frequency band, it is possible to compare with high reliability even an object having a complicated structure in which the distribution of frequency components changes according to the applied external force. Furthermore, the time from the detection of the external force to the detection of the detection signal is measured to determine the distance from the object to the signal detection means from the speed of the sound, and the distance between the object and the signal detection means is in the reference state. Since the comparison is made after correcting to the current state, the comparison can be performed without being affected by the distance between the signal detection means and the object.
As described above, the reliability of the inspection can be improved.

A signal detecting means for detecting a sound generated from the object to which the external force is applied by the external force applying means as a detection signal, and the transmission of the vibration from the external force applying means to the external force applying means is attenuated to a predetermined value or less. External force detecting means for detecting the magnitude of the external force fixed as described above, converting means for converting the detection signal into a time series signal for each of a plurality of predetermined frequency bands, and extracting the maximum value of the time series signal for each frequency band Extracting means, comparing means for comparing each maximum value with a preset reference value, and correcting at least one of each detection signal, time-series signal, maximum value, and reference value according to the magnitude of the external force. Since it is provided with a correction means, the signal detection means is fixed to the external force applying means so as to attenuate the transmission of vibration from the external force applying means to a predetermined value or less. No. with almost be a constant distance between the detecting means it can be prevented errors due transmission of sound from the external force applying unit to the signal detecting means, it is possible to improve the reliability of the inspection.

Further, a signal detecting means for detecting a sound generated from an object to which an external force is applied by the external force applying means as a detection signal, and a detection signal maximum value detecting means for detecting a maximum value of the detection signal as a detection signal maximum value. Converting means for converting a detection signal into a time series signal for each of a plurality of predetermined frequency bands; extracting means for extracting a maximum value of the time series signal for each frequency band; and a time series signal based on the detection signal maximum value. And a comparing means for comparing each detected signal maximum value ratio with a preset reference value. Therefore, if the ratio of the maximum value of the time series signal to the ratio of the maximum value of the detection signal is obtained based on the maximum value of the detection signal, the comparison is performed without being affected by the strength of the excitation force or the size of the detection signal. Bets can be, it is possible to improve the reliability of the inspection.

Further, a signal detecting means for detecting a sound generated from an object to which an external force is applied by the external force applying means as a detection signal, and a converting means for converting the detection signal into a time series signal for each of a plurality of predetermined frequency bands. Extracting means for extracting the maximum value of the time-series signal for each frequency band, frequency band maximum value detecting means for detecting the largest value of the maximum values of the time-series signal as the frequency band maximum value, and frequency band maximum value Means for calculating the ratio of the maximum value of each time-series signal as the ratio of the maximum value to the frequency band with reference to the frequency band maximum value ratio calculating means, and comparing means for comparing each of the frequency band maximum value ratios with a preset reference value Since it is equipped with
If the ratio of the maximum value of each time-series signal to the maximum value of the frequency band is determined based on the maximum value of the frequency band, the comparison can be performed without being affected by the strength of the excitation force or the size of the detection signal. In addition, the reliability of inspection can be improved.

[0103] Signal detection means for detecting, as a detection signal, a sound generated from the object to which the external force is applied by the external force application means, and conversion means for converting the detection signal into a time series signal for each of a plurality of predetermined frequency bands. Extraction means for extracting the maximum value of the time-series signal for each frequency band, and the maximum value of the time-series signal after a predetermined time has elapsed since the application of the external force after the predetermined time has elapsed for each frequency band. The maximum value extracting means after a lapse of a predetermined time to extract as a value, the attenuation rate calculating means for obtaining a ratio of the maximum value after a lapse of a predetermined time as an attenuation rate based on the maximum value of the time-series signal, and each attenuation rate is preset. Since it is provided with a comparison means for comparing with the reference value, if the ratio of the maximum value after a lapse of a predetermined time is determined as the attenuation rate based on the maximum value of the time series signal, the magnitude of the excitation force and the magnitude of the detection signal can be obtained. Comparison without being affected can be performed, it is possible to improve the reliability of the inspection.

Further, a signal detecting means for detecting, as a detection signal, a sound generated from the object to which the external force is applied by the external force applying means, and a converting means for converting the detection signal into a time series signal for each of a plurality of predetermined frequency bands. Extracting means for extracting the maximum value of the time-series signal for each frequency band; effective value calculating means for calculating the effective value of the time-series signal; and an effective value of the time-series signal based on the maximum value of the time-series signal. Since it has time measuring means for measuring the decay time until the ratio reaches a predetermined value and comparing means for comparing each decay time with a preset reference value, the maximum value of the time-series signal is used as a reference. By measuring the decay time until the ratio of the effective value of the time series signal becomes a predetermined value and comparing it with the reference value, the comparison is performed without being affected by the strength of the excitation force or the magnitude of the detection signal. Can be inspected with reliability It is possible to improve.

The comparing means sets the reference value range based on a plurality of detection signals obtained when the object is in a predetermined state, and the reference value range deviates from the predetermined range. 7. The method according to claim 1, further comprising a comparison result excluding unit for excluding a comparison result of the frequency band comparing unit. When the variation of the sound to be performed is large, the setting range of the set reference value is wide, but when the range is too wide, it can be considered as a noise component generated from outside the object and is not suitable to be adopted as the reference value. Therefore, the reliability of the test can be improved by excluding the comparison result of the comparator in the frequency band from the determination target.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a tapping sound inspection apparatus according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a tapping sound inspection apparatus according to another embodiment of the present invention.

FIG. 3 is a configuration diagram of a tapping sound inspection apparatus according to another embodiment of the present invention.

FIG. 4 is a configuration diagram of a tapping sound inspection apparatus according to another embodiment of the present invention.

FIG. 5 is a configuration diagram of a tapping sound inspection apparatus according to another embodiment of the present invention.

FIG. 6 is a configuration diagram of a tapping sound inspection apparatus according to another embodiment of the present invention.

FIG. 7 is a configuration diagram of a tapping sound inspection apparatus according to another embodiment of the present invention.

FIG. 8 is a configuration diagram of a conventional tapping sound inspection device.

[Explanation of symbols]

1 can, 2 hammer, 3 microphone, 5 analog BPF, 7 peak hold, 8 corrector, 9 comparator, 10 reference value setting device, 11 vibration sensor, 14 peak hold, 15 ratio calculator, 16 reference value setting device, 17 Trigger detector, 20 time difference measuring instrument, 21
Ratio calculator, 22 maximum value extractor, 23 timer, 24
Ratio comparator, 25 hour measuring device, 27 reference value setting device, 28 set value width comparator, 33 microphone, 34
Gloves, 36, 37 Peak hold, 38 RMS calculator, 41 Compensator.

Claims (7)

[Claims] 1. A signal detecting means for detecting a sound generated from an object to which an external force is applied by an external force applying means as a detection signal, and an external force detecting means for detecting a magnitude of the external force applied by the external force applying means. A time measuring means for measuring a time from when the external force is detected to when the detection signal is detected, a conversion means for converting the detection signal into a time series signal for each of a plurality of predetermined frequency bands, and the time series Extraction means for extracting the maximum value of the signal for each frequency band, comparison means for comparing each of the maximum values with a preset reference value, and each of the detection signals according to the magnitude of the external force and the time, At least one of a time-series signal, a maximum value, and a reference value
A hammering sound inspection apparatus comprising: 2. A signal detecting means for detecting, as a detection signal, a sound generated from an object to which an external force is applied by an external force applying means, and transmitting the vibration from the external force applying means to the external force applying means to a predetermined value or less. External force detecting means fixed to attenuate and detecting the magnitude of the external force, converting means for converting the detection signal into a time series signal for each of a plurality of predetermined frequency bands, and a maximum value of the time series signal Extraction means for extracting for each frequency band, comparison means for comparing each of the maximum values with a preset reference value, and each of the detection signals, the time-series signal, the maximum value, depending on the magnitude of the external force, and A tapping sound inspection apparatus, comprising: a correction unit configured to correct at least one of the reference values. 3. A signal detecting means for detecting a sound generated from an object to which an external force is applied by an external force applying means as a detection signal, and a detection signal maximum value detection for detecting a maximum value of the detection signal as a detection signal maximum value. Means, conversion means for converting the detection signal into a time-series signal for each of a plurality of predetermined frequency bands, extraction means for extracting the maximum value of the time-series signal for each frequency band, the detection signal maximum value A detection signal maximum value ratio calculating means for obtaining a ratio of the maximum value of the time-series signal as a reference signal maximum value ratio as a reference; and a comparing means for comparing each of the detection signal maximum value ratios with a preset reference value. A hammering inspection device comprising: 4. A signal detecting means for detecting a sound generated from an object to which an external force is applied by an external force applying means as a detection signal, and a conversion for converting the detection signal into a time series signal for each of a plurality of predetermined frequency bands. Means, extraction means for extracting the maximum value of the time series signal for each frequency band, frequency band maximum value detection means for detecting the largest value of the maximum values of the time series signal as the frequency band maximum value, Frequency band maximum value ratio calculating means for calculating the ratio of the maximum value of each time-series signal as a frequency band maximum value ratio based on the frequency band maximum value, and each frequency band maximum value ratio is preset. A hitting sound inspection device comprising: a comparison unit for comparing with a reference value. 5. A signal detecting means for detecting a sound generated from an object to which an external force is applied by an external force applying means as a detection signal, and a conversion for converting the detection signal into a time series signal for each of a plurality of predetermined frequency bands. Means, extracting means for extracting the maximum value of the time-series signal for each of the frequency bands, and extracting the maximum value of the time-series signal for each of the frequency bands after a predetermined time has elapsed since the external force was applied. A maximum value extraction means after a predetermined time elapses to extract as a maximum value after a predetermined time elapses, and an attenuation rate calculation means for obtaining a rate of the maximum value after the predetermined time elapses as an attenuation rate based on the maximum value of the time-series signal, A hitting sound inspection apparatus comprising: a comparing unit that compares each of the attenuation rates with a preset reference value. 6. A signal detecting means for detecting a sound generated from an object to which an external force is applied by an external force applying means as a detection signal, and a conversion for converting the detection signal into a time series signal for each of a plurality of predetermined frequency bands. Means, extraction means for extracting the maximum value of the time-series signal for each of the frequency bands, effective value calculation means for calculating the effective value of the time-series signal, and A tapping sound inspecting apparatus comprising: a time measuring means for measuring a decay time until a ratio of an effective value of a series signal reaches a predetermined value; and a comparing means for comparing each of the decay times with a preset reference value. 7. A comparison means for setting a range of a reference value based on a plurality of detection signals obtained when the object is in a predetermined state, wherein the range of the reference value deviates from the predetermined range. 7. The hitting sound inspection device according to claim 1, further comprising a comparison result exclusion unit that excludes a comparison result of the comparison unit of the frequency band.