JP2007248184A - Impact sound detection method and detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an impact sound detection method and an impact sound detector capable of detecting impact sound precisely. <P>SOLUTION: An inputted sound signal is subjected to absolute value processing by an absolute value processing section 4; the envelope is obtained by an envelope processing section 5; the cross correlation between the waveform of the envelope, and reference waveform obtained by performing the similar processing to the impact sound is computed by a cross correlation computation section 7; and it is determined that the sound is impact sound when the computation result is larger than a threshold; and a detection signal is outputted to the outside from an output section 8. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method and an apparatus for detecting an impact sound generated when an object hits the object.

  2. Description of the Related Art Conventionally, there is an inspection device that takes in sound or vibration from an inspection object by a sensor and inspects whether the inspection object is normal or abnormal, and is used for product inspection, facility diagnosis, and the like.

As a method for detecting the sound of such an inspection object, for example, as disclosed in Patent Document 1, a cross-correlation calculation is performed with a reference sound using the frequency component and amplitude component of the sound, and the calculation result And a threshold value.
JP-A-1-937974

  In the method of obtaining the cross-correlation between the sound of the inspection object and the reference sound as in Patent Document 1, the sound to be detected is, for example, as shown in the waveform of the sound signal in FIG. In the case of an impact sound having a large change, in particular, an impact sound whose sound duration T changes, if a time lag occurs between the amplitude of the sound to be inspected and the amplitude of the reference sound, The correlation calculation result changes greatly, and it is difficult to detect with high accuracy. In particular, it becomes more difficult in applications where the timing at which the impact sound is input changes.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an impact sound detection method and a detection apparatus that can accurately detect even an impact sound.

  (1) The impact sound detection method of the present invention is an impact sound detection method for detecting an impact sound from a sound signal, wherein the sound signal is subjected to absolute value processing to obtain an envelope, and the obtained waveform of the envelope And calculating a cross-correlation between the reference waveform corresponding to the impact sound and determining whether the sound is an impact sound based on the result of the calculation.

  The impact sound is a sound generated by hitting an object.For example, various sounds such as a sound generated by a collision between parts such as a fitting sound of parts, a sound generated when a door is closed, and a sound generated by rattling. In general, the sound has a large amplitude change in a short time.

  The sound signal is preferably captured by a microphone or a vibration sensor.

  The absolute value processing is processing in which all sound signals that change in the positive and negative directions from the center of the amplitude are set in the positive direction. For example, the absolute value processing can be performed by full-wave rectification.

  The reference waveform is a waveform corresponding to the impact sound, and is preferably the waveform of the envelope when the sound signal of the impact sound is subjected to absolute value processing to obtain the envelope, and the sound signal of the impact sound is A waveform obtained by averaging a plurality of reference waveforms obtained by acquiring a plurality of times may be used as a final reference waveform.

  By calculating the cross correlation, the similarity between the reference waveform and the envelope waveform can be obtained.

  According to the impact sound detection method of the present invention, the sound signal is subjected to absolute value processing to obtain an envelope, and the impact sound is detected from the cross-correlation between the envelope waveform and the reference waveform corresponding to the impact sound. Even an impact sound with a large change or a change in duration can be detected with high accuracy by using the waveform of the envelope.

 (2) The impact sound detection method of the present invention is an impact sound detection method for detecting an impact sound from a sound signal, wherein the sound signal is subjected to absolute value processing to obtain an envelope, and the obtained waveform of the envelope And a reference waveform corresponding to the impact sound, a step of determining whether or not the impact sound is detected based on a result of the calculation, and a detection timing. A feature amount is calculated from a sound signal of a predetermined period including the detection timing, and a step of determining whether or not the sound is an impact sound based on the calculated feature amount.

  The detection timing refers to a timing at which an impact sound is to be detected. This timing is a timing at which the sound signal is assumed to be an impact sound from the result of the cross-correlation calculation.

The predetermined period including the detection timing may be a predetermined period before and after the detection timing, may be a predetermined period after the detection timing, or may be a predetermined period before the detection timing. However, it is preferable to include the sound signal used for the cross-correlation calculation for determining the detection timing. Further, the predetermined period only needs to be able to extract the feature amount from the sound signal of the predetermined period, and may be the duration of the impact sound that is the detection target.
The feature amount is preferably an amount representing the feature of the impact sound. For example, the feature amount may be the number of peaks of the sound signal changing in the positive or negative direction from the center of the amplitude, the difference between adjacent peaks, or the peak value. Alternatively, the sound signal may be converted into frequency axis data by FET (Fast Fourier Transform), and a specific frequency band component may be extracted as a feature amount based on the frequency axis data.
According to the impact sound detection method of the present invention, when a sound signal is assumed to be an impact sound from the result of the cross-correlation calculation, whether or not it is an impact sound by extracting a feature amount from the sound signal of a predetermined period including the timing. Therefore, the detection accuracy of the impact sound is improved as compared with the configuration in which it is determined whether or not the impact sound is based only on the result of the cross-correlation calculation.

  (3) One embodiment of the impact sound detection method of the present invention includes a step of removing frequency components other than a predetermined band from the sound signal.

  The predetermined band refers to a band including a sound signal of an impact sound.

  According to this embodiment, frequency components other than the predetermined band in which the sound signal of the impact sound is included are removed, and the envelope value is obtained by performing absolute value processing on the sound signal of the predetermined band, and a cross correlation operation or the like is performed. Processing can be performed.

  (4) In one embodiment of the impact sound detection method of the present invention described in (1) above, the step of determining whether or not the impact sound is based on the result of the calculation includes the result of the calculation and a threshold value. And a step of determining that the sound is an impact sound when the result of the calculation is larger than the threshold value.

  According to this embodiment, when the result of the cross-correlation calculation is larger than the threshold value, that is, when the waveform of the envelope and the reference waveform corresponding to the impact sound are similar beyond the similarity corresponding to the threshold value, It can be determined as an impact sound.

  (5) In one embodiment of the impact sound detection method of the present invention described in (2) above, the step of determining whether or not the impact sound detection timing is based on the result of the calculation includes the step of Comparing the result with a threshold value, and determining that it is the impact sound detection timing when the result of the calculation is greater than the threshold value.

  According to this embodiment, when the result of the cross-correlation calculation is larger than the threshold value, that is, when the waveform of the envelope and the reference waveform corresponding to the impact sound are more similar than the similarity corresponding to the threshold value, Since it is assumed that it is an impact sound, it is possible to finally determine whether or not it is an impact sound by calculating the feature amount from the sound signals before and after that timing as the detection timing.

  (6) The impact sound detection device of the present invention is an impact sound detection device that detects an impact sound from an input sound signal, the input unit to which the sound signal is input, and the sound signal from the input unit. Is subjected to absolute value processing to obtain an envelope, a cross-correlation between the waveform of the envelope and a reference waveform corresponding to the impact sound is calculated, and it is determined whether the sound is an impact sound based on the calculation result A processing unit and an output unit that outputs a detection signal when the processing unit determines that the sound is an impact sound are included.

  According to the impact sound detection device of the present invention, the sound signal is subjected to absolute value processing to obtain an envelope, and the impact sound is detected from the cross-correlation between the envelope waveform and the reference waveform corresponding to the impact sound. Even an impact sound with a large change or a change in duration can be detected with high accuracy by using the waveform of the envelope.

  (7) The impact sound detection device according to the present invention is an impact sound detection device that detects an impact sound from an input sound signal, the input unit to which the sound signal is input, and the sound signal from the input unit. Whether or not it is the detection timing of the impact sound based on the result of calculating the cross-correlation between the waveform of the envelope and the reference waveform corresponding to the impact sound. When it is determined that it is the detection timing, the feature amount is calculated from the sound signal of a predetermined period including the detection timing, and it is determined whether or not the sound is an impact sound based on the feature amount. A processing unit and an output unit that outputs a detection signal when the processing unit determines that the sound is an impact sound are included.

  According to the impact sound detection device of the present invention, when an impact sound is assumed from the result of the cross-correlation calculation, a feature amount is extracted from the sound signal of a predetermined period including the timing to finally determine whether or not the impact sound. Therefore, the detection accuracy of the impact sound is improved as compared with the configuration in which it is determined whether the sound is the impact sound or not from the result of the cross-correlation calculation.

  (8) In one embodiment of the impact sound detection device of the present invention, the processing unit includes a waveform processing unit that obtains an envelope by performing absolute value processing on the sound signal from the input unit, and the impact sound. A reference waveform storage unit that stores a corresponding reference waveform, and a cross-correlation calculation unit that calculates a cross-correlation between the reference waveform and the envelope waveform are included.

  According to this embodiment, the waveform processor can perform absolute value processing on the sound signal to obtain an envelope, and the cross-correlation calculator can calculate the cross-correlation between the waveform of the envelope and the reference waveform.

  According to the present invention, the sound signal is subjected to absolute value processing to obtain an envelope, and the impact sound is detected from the cross-correlation between the waveform of the envelope and the reference waveform corresponding to the impact sound. Even an impact sound whose duration changes can be accurately detected by using the envelope waveform.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of an impact sound detection apparatus 1 according to the present invention.

  The impact sound detection device 1 includes an input unit 2 including an A / D converter for A / D converting an analog sound signal input from a microphone (not shown), and processes the sound signal from the input unit 2 A processing unit 15 that determines whether or not the sound is an impact sound, and an output unit 8 that outputs a detection signal to the outside when the processing unit 15 determines that the sound is an impact sound. Consists of a computer.

  The processing unit 15 takes the absolute value of the output from the filter unit 3 that passes only the frequency component of a predetermined band including the impact sound to be detected in the digital signal from the input unit 2 and the filter unit 3. An absolute value processing unit 4, an envelope processing unit 5 for obtaining an envelope of the output of the absolute value processing unit 4, a reference waveform storage unit 6 in which a reference waveform corresponding to an impact sound is stored in advance, and an envelope processing unit 5, the cross-correlation calculation unit 7 that calculates the cross-correlation between the waveform of the envelope from the reference waveform and the reference waveform, and the calculation result of the cross-correlation calculation unit 7 is compared with a threshold value to determine whether the sound is an impact sound And a determination unit 16.

  The filter unit 3 removes frequency components other than the predetermined band including the impact sound, and is configured by, for example, a FIR filter that is a high-pass filter of a fourth order Butterworth.

  The absolute value processing unit 4 obtains the absolute value of the sound signal shown in FIG. 2A, for example, and makes the signal center in the positive direction with the center of the amplitude being 0 level. The absolute value waveform shown in FIG. 2B is rectified. Note that full-wave rectification may be performed after removing the DC component.

  Further, the envelope processing unit 5 takes out the envelope of the absolute value waveform in FIG. 2B as shown in FIG. 2C through, for example, a low-pass filter that passes only a signal in a low frequency region. In FIG. 2, a trigger and a predetermined period T <b> 1 that will be described in the second embodiment to be described later are also shown.

  The absolute value processing unit 4 and the envelope processing unit 5 constitute a waveform processing unit.

  The reference waveform is a waveform obtained by inputting an impact sound as a detection target to the input unit 2 and processing by the filter unit 3, the absolute value processing unit 4, and the envelope processing unit 5. For example, the impact sound is input a plurality of times. A waveform obtained by averaging the plurality of reference waveforms obtained in this manner is stored in advance in the reference waveform storage unit 6 as a final reference waveform.

  The cross-correlation calculation unit 7 is the reference waveform of the reference waveform storage unit 6 and the waveform of the envelope of the sound signal input from the input unit 2 and processed by the filter unit 3, the absolute value processing unit 4 and the envelope processing unit 5. The cross-correlation with is calculated.

  In general, the cross-correlation Rxy (t) between the signal X (t) and the signal Y (t) is defined as follows.

相互相関演算部７は、包絡線処理部５からの包絡線の波形と参照波形との間で、所定のサンプリング点毎に乗算を行なってその乗算結果の総和を演算するものであり、この実施形態では、例えば、５１２タップのＦＩＲフィルタから構成される。

The cross-correlation calculation unit 7 performs multiplication for each predetermined sampling point between the waveform of the envelope from the envelope processing unit 5 and the reference waveform, and calculates the sum of the multiplication results. In the form, for example, it is constituted by a 512-tap FIR filter.

  The larger the sum of the multiplication results, that is, the calculation result of the cross-correlation calculation unit 7, the higher the similarity between the envelope waveform and the reference waveform.

  The determination unit 16 compares a predetermined threshold value with the calculation result of the cross-correlation calculation unit 7. When the calculation result exceeds the threshold value, the sound signal is determined to be an impact sound and a determination output is output. Give to 8.

  The output unit 8 outputs a detection signal to the outside in response to a determination output indicating that the sound is an impact sound.

  FIG. 3 is a diagram illustrating a calculation result of the cross correlation calculation unit 7 and a detection signal output from the output unit 8.

  FIG. 6A shows temporal changes in the calculation result of the cross-correlation calculation unit 7, where the horizontal axis indicates time and the vertical axis indicates the calculation result.

  A sound signal that is not an impact sound is input to the input unit 2 and processed by the filter unit 3, the absolute value processing unit 4, and the envelope processing unit 5 as described above, and the cross-correlation with the reference waveform is performed by the cross-correlation calculation unit 7. Is calculated, the result of the calculation becomes a small value, for example, as indicated by the broken line in FIG. 3A, and the detection signal is not output without exceeding the threshold value.

  On the other hand, an impact sound signal is input to the input unit 2 and processed by the filter unit 3, the absolute value processing unit 4 and the envelope processing unit 5. When the correlation is calculated, as shown by the solid line in FIG. 3 (a), the calculation result of the cross correlation gradually increases as the sound signal of the impact sound is input and exceeds the threshold value. As shown in FIG. 5B, it is determined that the sound is a sound, and a high level detection signal is output for a certain period (Ton).

  In this way, the envelope of the input sound signal is obtained, and the impact sound is detected by performing a cross-correlation operation between the envelope waveform and the reference waveform. Even so, it can be accurately detected.

  That is, since the cross-correlation is calculated using the envelope, even if there is a slight time lag between the input sound signal and the reference waveform, the result of the cross-correlation calculation does not change greatly. The impact sound can be detected with high accuracy.

  In addition, it is possible to detect impact sound from sound signals continuously picked up by a microphone, etc., and to detect impact sound accurately even in applications where the impact sound input timing changes. Can do.

(Embodiment 2)
FIG. 4 is a block diagram showing a configuration of an impact sound detection apparatus 10 according to another embodiment of the present invention, and portions corresponding to the above-described embodiment are denoted by the same reference numerals.

  In this embodiment, the determination output from the determination unit 16 of the above-described embodiment is used as a trigger to calculate the feature amount of the sound signal before and after that, and based on this feature amount, a final determination as to whether or not the sound is an impact sound is performed. By making the determination, the detection accuracy of the impact sound is enhanced.

  In other words, the impact sound detection device 10 of this embodiment processes an input unit 2 including an A / D converter for A / D converting an input analog sound signal, and processes the sound signal from the input unit 2. A processing unit 17 that determines whether or not the sound is an impact sound and an output unit 8 that outputs a detection signal to the outside when the processing unit 17 determines that the sound is an impact sound are provided.

  Similarly to the above-described embodiment, the processing unit 17 includes a filter unit 3 that allows only a frequency component in a predetermined band including a shock sound to be detected among digital signals from the input unit 2, and the filter unit 3. An absolute value processing unit 4 that takes the absolute value of the output from the signal, an envelope processing unit 5 that obtains an envelope of the output of the absolute value processing unit 4, and a reference waveform storage in which a reference waveform corresponding to an impact sound is stored Section 6, cross-correlation calculation section 7 that calculates the cross-correlation between the waveform of the envelope from envelope processing section 5 and the reference waveform, and the calculation result of this cross-correlation calculation section 7 and the threshold value are compared, and the impact sound And a timing determination unit 16 that determines whether or not the detection timing is present, and is similar to the above-described embodiment except that the determination output of the timing determination unit 16 is used as an internal detection timing trigger.

  Further, in this embodiment, the processing unit 17 detects the detection in response to the data storage unit 11 storing the sound signal from the input unit 2 and the determination output indicating the detection timing from the timing determination unit 16. A feature amount calculation unit 12 that reads out a sound signal from the data storage unit 11 and calculates and extracts a feature amount in a predetermined period including timing, in this example, including a detection period before and after the detection timing, and the feature amount calculation unit And an impact sound determination unit 18 for determining whether or not the sound is an impact sound based on the feature amount from 12.

  The data storage unit 11 has a capacity capable of storing sound signals over a predetermined period, and sequentially updates and stores input sound signals.

  The timing determination unit 16 compares the calculation result of the cross-correlation calculation unit 7 with a threshold value and gives a determination output when the calculation result exceeds the threshold value, as in the above-described embodiment shown in FIG. . Since this determination output is output for a sound signal determined to be an impact sound, in this embodiment, the feature amount calculation unit 12 uses this determination output as a trigger for the detection timing of the impact sound. The sound signal of a predetermined period before and after the detection timing including the detection timing is read from the data storage unit 11 to extract the feature amount, and based on the feature amount, it is finally determined whether the sound signal of the predetermined period is an impact sound. It is determined automatically. For example, as shown in FIG. 2A, when a trigger, which is a determination output of the timing determination unit 16, is output at a timing indicated by an arrow, a sound signal over a predetermined period T1 including the timing is read out. It will be.

  The feature amount calculation unit 12 removes noise components contained in the sound signal data of the predetermined period T1 read from the data storage unit 11 with a bandpass filter or the like, and then the feature amount, for example, the peak of the sound signal that changes to positive or negative. , The difference between adjacent peaks, the peak value, etc. are extracted.

  The impact sound determination unit 18 stores in advance, for example, threshold values such as the number of peaks and peak values calculated and extracted for the impact sound to be detected. The number of peaks, the peak value, and the like are compared with corresponding threshold values to determine whether or not the sound is an impact sound. For example, when the number of peaks and the peak value are within the upper and lower threshold values, it is determined that the sound is an impact sound.

  The output unit 8 outputs a detection signal to the outside when it is determined as an impact sound based on the determination output of the impact sound determination unit 18.

  As described above, in the same manner as in the above-described embodiment, when it is determined that the sound is an impact sound, the timing is set as the detection timing of the impact sound, and the feature amount of the sound signal in the predetermined period before and after the detection timing is calculated. Since it is finally determined whether or not it is an impact sound after extraction, it is possible to detect the impact sound with higher accuracy.

  The feature amount is not limited to the number of peaks and the peak value. For example, the feature amount is converted into frequency axis data by FET (Fast Fourier Transform), and a specific frequency band component is extracted as the feature amount based on the frequency axis data. Further, a feature amount may be extracted by employing a method using a general vibration analysis index or a statistical function.

  In addition, the feature amount calculation unit 12 extracts a plurality of feature amounts, not limited to one type of feature amount, and the impact sound determination unit 18 combines the plurality of feature amounts to determine whether or not the sound is an impact sound. It may be determined automatically.

  The present invention is useful for detecting impact sound.

It is a block diagram which shows the structure of the impact sound detection apparatus of this invention. It is a wave form diagram for demonstrating the process of a sound signal. It is a figure which shows the relationship between the calculation result of a cross correlation calculating part, and a detection signal. It is a block diagram which shows the structure of the impact sound detection apparatus of other embodiment of this invention. It is a wave form diagram which shows the sound signal of an impact sound.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,10 Impact sound detection apparatus 2 Input part 15, 17 Processing part 8 Output part 3 Filter part 4 Absolute value processing part 5 Envelope processing part 6 Reference waveform memory | storage part 7 Cross correlation calculation part 12 Feature-value calculation part

Claims (8)

An impact sound detection method for detecting an impact sound from a sound signal,
Obtaining an envelope by performing absolute value processing on the sound signal; and
Calculating a cross-correlation between the waveform of the obtained envelope and a reference waveform corresponding to the impact sound;
Determining whether the sound is an impact sound based on the result of the calculation;
A method for detecting an impact sound, comprising: An impact sound detection method for detecting an impact sound from a sound signal,
Obtaining an envelope by performing absolute value processing on the sound signal; and
Calculating a cross-correlation between the waveform of the obtained envelope and a reference waveform corresponding to the impact sound;
Determining whether or not the detection timing of the impact sound based on the result of the calculation;
A step of calculating a feature amount from a sound signal of a predetermined period including the detection timing when it is determined to be the detection timing;
Determining whether or not the sound is an impact sound based on the calculated feature value;
A method for detecting an impact sound, comprising:   The impact sound detection method according to claim 1, further comprising a step of removing frequency components other than a predetermined band from the sound signal.   The step of determining whether or not the sound is an impact sound based on the result of the calculation includes the step of comparing the result of the calculation with a threshold value, and the impact sound when the result of the calculation is greater than the threshold value. The impact sound detection method according to claim 1, further comprising a step of determining that   The step of determining whether or not the detection timing of impact sound is based on the result of the calculation is a step of comparing the result of the calculation with a threshold value, and when the result of the calculation is greater than the threshold value. The impact sound detection method according to claim 2, further comprising the step of determining that it is the detection timing of the impact sound. An impact sound detection device for detecting an impact sound from an input sound signal,
An input unit to which the sound signal is input;
The sound signal from the input unit is subjected to absolute value processing to obtain an envelope, a cross-correlation between the waveform of the envelope and a reference waveform corresponding to the shock sound is calculated, and an impact sound is calculated based on the calculation result. A processing unit for determining whether or not
An output unit that outputs a detection signal when the processing unit determines that the sound is an impact sound;
An impact sound detection device comprising: An impact sound detection device for detecting an impact sound from an input sound signal,
An input unit to which the sound signal is input;
The sound signal from the input unit is subjected to absolute value processing to obtain an envelope, a cross-correlation between the waveform of the envelope and a reference waveform corresponding to the impact sound is calculated, and an impact is calculated based on the calculation result. It is determined whether or not it is sound detection timing. When the detection timing is determined, a feature amount is calculated from a sound signal of a predetermined period including the detection timing, and an impact sound is calculated based on the feature amount. A processing unit for determining whether or not
An output unit that outputs a detection signal when the processing unit determines that the sound is an impact sound;
An impact sound detection device comprising:   The processing unit includes a waveform processing unit that obtains an envelope by performing absolute value processing on the sound signal from the input unit, a reference waveform storage unit that stores a reference waveform corresponding to the impact sound, and the reference waveform. The impact sound detection device according to claim 6, further comprising a cross-correlation calculating unit that calculates a cross-correlation with the waveform of the envelope.

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