JP2021081354A - Acoustic characteristic measuring system, acoustic characteristic measuring method, and acoustic characteristic measuring program - Google Patents

Abstract

To provide an acoustic characteristic measuring system with which it is possible to extract, from a collected sound signal that includes noise, a measurement object sound that is generated by a measurement object.SOLUTION: An acoustic characteristic measuring system comprises a first microphone, a second microphone, first collected sound spectrum calculation means, second collected sound spectrum calculation means, measurement object sound on/off control means, and measurement object sound spectrum calculation means. The first microphone, the second microphone and the measurement object are arranged in a prescribed physical relationship. The measurement object sound spectrum calculation means holds the measurement object sound spectrum collected by the first and second microphones in a noise-free environment as first and second reference spectra. Then, when the measurement object sound is turned on/off, it removes the influence of noise and calculates a measurement object sound spectrum using the first and second collected sound spectra when the measurement object sound is turned on in a specific session, the first and second collected sound spectra when the measurement object sound is turned off before and after the session, and the first and second reference spectra.SELECTED DRAWING: Figure 1

Description

The present invention relates to an acoustic characteristic measurement system, an acoustic characteristic measurement method, and an acoustic characteristic measurement program.

At the production site, there is a technique for judging the quality of a product based on the sound generated from the product. A large amount of noise is generated around the product to be measured due to the driving of a belt conveyor, an AGV (Automated Guided Vehicle), an electric driver, an equipment fan, etc., and a conversation between workers. Since the timing and position at which these noises are generated are not uniform, it is required to accurately measure the sound to be measured from the object to be measured by excluding the noise generated around the object to be measured.

Patent Document 1 discloses a noise measuring method using a unidirectional microphone and an omnidirectional microphone. In the technique of Patent Document 1, sound is collected by using a unidirectional microphone and an omnidirectional microphone, noise is removed by signal processing utilizing the difference in directivity, and only the sound to be measured is extracted. Specifically, the unidirectional microphone first collects only the measurement target sound (noise in this case) to acquire the first sound collection signal, and the omnidirectional microphone collects the measurement target sound and the surrounding environment sound. Sounds to acquire a second sound collection signal. Next, Fourier transform is performed on the first and second sound collection signals, and the first Fourier transform signal and the second Fourier transform signal are calculated. Next, the conjugate of the first Fourier transform signal is multiplied by the second Fourier transform signal, this is divided by the square of the first Fourier transform signal, and the calculation result is averaged. By this calculation, the noise component can be removed and a noise signal can be obtained.

Special Fair 05-043979

In Patent Document 1, it is assumed that the sound collected by the unidirectional microphone is the sound to be measured. However, in an actual environment, the position where the noise acoustic signal is generated is not constant, or the object that reflects the sound moves. As a result, noise is also mixed in the unidirectional microphone, and it may not be possible to accurately extract the sound to be measured.

An object of the present invention is to solve the above-mentioned problems and to provide an acoustic characteristic measurement system capable of extracting a measurement target sound generated by a measurement target from a sound collection signal containing noise.

In order to solve the above problems, the acoustic characteristic measurement system includes a first microphone, a second microphone, a first sound collection spectrum calculation means, a second sound collection spectrum calculation means, and a sound to be measured on / off control means. And has a sound spectrum calculation means for measurement. The first microphone, the second microphone, and the object to be measured are arranged in a predetermined positional relationship. The measurement target sound spectrum calculation means holds the spectrum of the measurement target sound collected by the first and second microphones in a noise-free environment as the first and second reference spectra. Then, when the sound to be measured is turned on / off, the first and second sound collection spectra at a specific time on, the first and second sound collection spectra at the time of off before and after that time, and the first and second sound collection spectra. The influence of noise is removed using the reference spectrum, and the sound spectrum to be measured is calculated.

According to the present invention, it is possible to provide an acoustic characteristic measurement system capable of extracting a measurement target sound generated by a measurement target from a sound collection signal containing noise.

It is a block diagram which shows the structure of the acoustic characteristic measurement system of 1st Embodiment. It is a block diagram which shows the structure of the acoustic characteristic measurement system of 2nd Embodiment. It is a schematic diagram which shows the example of the arrangement of the acoustic characteristic measurement system of 2nd Embodiment, a measurement object and a noise source. It is a timing chart in the reference signal measurement of the 2nd Embodiment. It is a timing chart in the acoustic characteristic measurement of the 2nd Embodiment. It is a schematic diagram which shows the signal flow in the reference signal measurement of 2nd Embodiment. It is a schematic diagram which shows the signal flow at the time of the measurement target sound on of the 2nd Embodiment. It is a schematic diagram which shows the signal flow at the time of the measurement target sound off of the 2nd Embodiment. It is a flowchart which shows the operation of the characteristic measurement of 2nd Embodiment. It is a block diagram which shows an example of the hardware composition of the acoustic characteristic measuring apparatus of 2nd Embodiment. It is a schematic diagram which shows the signal flow at the time of the measurement target sound off of the 3rd Embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, although the embodiments described below have technically preferable limitations for carrying out the present invention, the scope of the invention is not limited to the following. Note that similar components in each drawing may be numbered the same and description may be omitted. Further, in the following embodiments, repeated explanations may be omitted for similar configurations and operations. Further, the direction of the arrow in the drawing shows an example, and does not limit the direction of the signal between blocks.

(First Embodiment)
First, the acoustic characteristic measurement system according to the first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an example of the configuration of the acoustic characteristic measurement system 1 of the present embodiment. The acoustic characteristic measurement system 1 includes a first microphone 10, a second microphone 20, a first sound collection spectrum calculation means 30, a second sound collection spectrum calculation means 40, a sound to be measured on / off control means 50, and the like. It has a sound spectrum calculation means 60 to be measured.

The first microphone 10 is arranged at a predetermined position to collect sound, converts the collected sound into an electric signal, and outputs the first sound collection signal to the first sound collection spectrum calculation means 30. The second microphone 20 collects sound at a position having a predetermined positional relationship with the first microphone, converts the collected sound into an electric signal, and uses the second sound collection spectrum calculation means 40 as the second sound collection signal. Output. The first microphone and the second microphone are arranged so as to have a predetermined positional relationship, and further, the positional relationship with the position where the measurement object 70 that generates the measurement target sound is arranged also has a predetermined positional relationship. Have been placed. That is, the positional relationship between the first microphone 10 and the second microphone 20 is fixed, and the measurement object 70 is also arranged at a predetermined position.

The first sound collection spectrum calculation means 30 converts the first sound collection signal collected by the first microphone to calculate the first sound collection spectrum. The second sound collection spectrum calculation means 40 converts the second sound collection signal collected by the second microphone to calculate the second sound collection spectrum.

The measurement target sound on / off control means 50 controls to turn on / off the measurement target sound at a predetermined cycle. The control method is arbitrary, but for example, when the object to be measured is an electrically operated object, the control may be such that the power supply of the object 70 to be measured is turned on / off.

The measurement target sound spectrum calculation means 60 holds a first reference spectrum calculated from the first sound collection signal and a second reference spectrum calculated from the second sound collection signal when noise is cut off. The acquisition of the first reference spectrum and the second reference spectrum can be performed by collecting the sound to be measured in a noise-free environment using, for example, a sound insulation box or the like. Acquisition of these reference spectra should be performed prior to measurement in a noisy environment.

Next, the measurement target sound spectrum calculation means 60 selects a specific time when the measurement target sound is repeatedly turned on / off. Then, the first sound collection spectrum and the second sound collection spectrum at the time of on are acquired. Further, the first sound collection spectrum and the second sound collection spectrum at the time of off before and after this specific time are acquired. Then, the first sound collection spectrum and the second sound collection spectrum at the time of on of the specific time, the first sound collection spectrum and the second sound collection spectrum at the time of off before and after the specific time, and the first reference spectrum and the first The sound spectrum to be measured is calculated using the two reference spectra. At this time, using the above data, the sound spectrum to be measured can be calculated by subtracting the noise spectrum from the first sound collection spectrum or the second sound collection spectrum when on. Here, in the above specific times, the ratio of the first sound collection spectrum and the second sound collection spectrum at a certain frequency is calculated, and the change of the ratio is equal to or less than a predetermined threshold value before and after on. decide. In the example of FIG. 1, it is assumed that the noise source 80 exists in the installation environment of the acoustic characteristic measurement system 1, but the noise source 80 shown in FIG. 1 is an example, and the noise source is limited to one. It's not a thing.

As described above, according to the present embodiment, it is possible to provide an acoustic characteristic measurement system capable of extracting the sound to be measured generated by the object to be measured from the sound collection signal containing noise.

(Second embodiment)
In this embodiment, a specific configuration and operation of the acoustic characteristic measurement system whose basic configuration is shown in the first embodiment will be described. FIG. 2 is a block diagram showing the configuration of the acoustic characteristic measurement system 1000 of the present embodiment. The acoustic characteristic measurement system 1000 includes an omnidirectional microphone 100, a directional microphone 200, an acoustic characteristic measurement device 300, and a sound to be measured on / off control device 400. The acoustic characteristic measuring device 300 includes a first Fourier transform processing unit 310, a second Fourier transform processing unit 320, a spectrum calculation unit 330, a storage unit 340, and a control unit 350. Further, the spectrum calculation unit 330 includes a reference spectrum acquisition unit 331, a calculation target rotation selection unit 332, and a measurement target sound spectrum calculation unit 333.

The omnidirectional microphone 100 collects omnidirectional sound, converts the collected sound into an electric signal, and outputs the first sound collection signal to the first Fourier transform processing unit 310. The directional microphone 200 collects directional sound, converts the collected sound into an electric signal, and outputs the second sound collection signal to the second Fourier transform processing unit 320. The omnidirectional microphone 100 and the directional microphone 200 are arranged in a predetermined positional relationship, and the measurement object described later is arranged so as to have a predetermined positional relationship with these microphones. That is, the omnidirectional microphone 100, the directional microphone 200, and the measurement object 70 are arranged so as to have a predetermined positional relationship.

The first Fourier transform processing unit 310 Fourier transforms the first sound collection signal collected by the omnidirectional microphone 100 at predetermined frame intervals, and calculates the first sound collection spectrum. Then, the calculated first sound collection spectrum is output to the spectrum calculation unit 330. The second Fourier transform processing unit 320 Fourier transforms the second sound collection signal collected by the directional microphone 200 at predetermined frame intervals, and calculates the second sound collection spectrum. Then, the calculated second sound collection spectrum is output to the spectrum calculation unit 330.

The measurement target sound on / off control device 400 controls to turn on / off the measurement target sound at a predetermined cycle. The control method is arbitrary, but for example, when the object to be measured is an electrically operated object, the control may be such that the power supply of the object to be measured is turned on / off.

The spectrum calculation unit 330 removes noise based on the first sound collection spectrum and the second sound collection spectrum, and calculates the measurement target sound spectrum. The reference spectrum is a spectrum of the sound to be measured collected in a noise-free environment, and the reference spectrum acquisition unit 331 has a first reference spectrum and a second reference spectrum for each of the first sound collection spectrum and the second sound collection spectrum. Obtain the reference spectrum. The calculation target time selection unit selects, under the control of the measurement target sound on / off control device 400, which time is to be the calculation target time when the measurement target sound repeats on and off. The measurement target sound spectrum calculation unit 333 removes noise by using the first sound collection spectrum and the second sound collection spectrum of the times selected by the calculation target time selection unit 332, and the first reference spectrum and the second reference spectrum. Calculate the measurement target sound spectrum. Details of each data used in the above calculation and the calculation method will be described later.

The storage unit 340 stores data such as a sound collection spectrum and a program for operating each unit. The control unit 350 controls transmission / reception of data, reading of a program, and the like.

Next, the operation of each part and the calculation method of each spectrum will be described. First, the sound to be measured and the noise will be described. FIG. 3 is a schematic diagram showing an example of arrangement of the acoustic characteristic measurement system 1000, the measurement object 500, and the noise source 600. First, the positional relationship between the omnidirectional microphone 100 and the directional microphone 200 is fixed. Next, the measurement object 500 is arranged so that the positional relationship with these microphones has a predetermined relationship. Naturally, the directional microphone 200 directs the sensitive direction toward the measurement object 500.

Here, it is assumed that there is a noise source 600 that generates noise. FIG. 3 shows an example in which the noise source 600 is located away from the acoustic characteristic measurement system 1000 and the object 500. The omnidirectional microphone 100 collects the sound to be measured 2 and the noise 3 from all directions. The directional microphone 200 collects the sound to be measured 2 and the noise 3 from a sensitive direction.

FIG. 4 is a timing chart showing on / off of the sound to be measured when the reference signal is measured. In FIG. 4, the generated signal generated in the measurement system is added to this timing chart. In the measurement of the reference signal, since the noise is blocked, the noise N ₀ when the measurement target sound is off is 0. On the other hand, the generated signal when the measurement target sound is on is S ₀ .

FIG. 5 is a timing chart showing on / off of the sound to be measured in the acoustic characteristic measurement. In FIG. 5, the generated signal generated in the measurement system is added to this timing chart. When the measurement target sound is off, only noise N is generated, and when the measurement target sound is on, the generated signal is S + N. Here, it is assumed that the number of times is counted each time the measurement target sound is turned on and off, and FIG. 5 shows a timing chart from the k-3rd off to the k + 3rd off. Although it is illustrated in FIG. 3 that noise is generated from one noise source 600, the noise N may be a mixture of a plurality of noises including noises from the environment, and this is hypothetical. It can be assumed that it originates from a noise source.

Here, the sound collection spectrum is formulated using the transfer function. The frequency, which is a variable, is f, the spectrum of the generation point of the sound to be measured is S (f), the first sound collection spectrum output from the first Fourier transform processing unit 310 is X (f), and the second Fourier transform processing unit 320. Let Y (f) be the second sound collection spectrum output from. Further, the transfer function from the measurement object 500 to the omnidirectional microphone 100 is A ₀ (f), and the transfer function from the directional microphone 200 is B ₀ (f). Furthermore, the spectrum of the noise generation point N (f), the noise source 600, a transfer function to the omnidirectional microphones 100 _{A n,} the transfer function to the directional microphones 200 and _B n (f). Further, the number of times is counted each time the sound to be measured is turned on or off, and the kth data is represented by the subscript of k.

FIG. 6 is a schematic diagram showing a data flow at the time of measuring the reference spectrum. The reference spectrum is a spectrum of the sound to be measured collected by the first microphone 100 and the second microphone 200 when a noise-free environment is created by using a sound insulation box or the like. _{Let S 0} (f) be the spectrum of the sound to be measured generated from the reference object to be measured. Then, it is assumed that the first microphone 100 is transmitted by the transfer function A ₀ (f) and the second microphone is transmitted by the transfer function B ₀ (f). From this definition, the first reference spectrum X ₀ (f) and the second reference spectrum Y ₀ (f) are expressed by the following equations. In the following formula, _{only X 0} (f) and Y ₀ (f) _{can be measured, and A 0} (f), B ₀ (f), and S ₀ (f) cannot be measured directly. Is.
X ₀ (f) = A ₀ (f) · S ₀ (f) (Equation 1)
Y ₀ (f) = B ₀ (f) · S ₀ (f) (Equation 2)

FIG. 7 is a schematic diagram showing a signal flow when the measurement target sound is on in the acoustic characteristic measurement. Since both the sound to be measured and the noise are input to the microphone, the first sound collection spectra X _n (f) and Y _n (f) can be expressed by the following equations. In this formula, a subscript k indicating that it is on for the kth time is added. Here, since _{the transfer function of Sk} (f) fixes the positional relationship between the two microphones and the object to be measured, the same A ₀ (f) and B ₀ (f) as in the reference spectrum measurement. There is. Further, the spectrum of noise generated by the noise source 600 is defined as Nk. The first term on the right side of the following equation, A ₀ (f) · _Sk (f), B ₀ (f) · _Sk (f), is a spectrum of the sound to be measured that does not include noise.
X _k (f) = A ₀ (f) · _Sk (f) + _Ank (f) · N _k (f) (Equation 3)
Y _k (f) = B ₀ (f) · _Sk (f) + B _nk (f) · N _k (f) (Equation 4)

FIG. 8 is a schematic diagram showing a signal flow when the measurement target sound is off in the acoustic characteristic measurement. Since only noise is input to the microphone, the first sound collection spectra X _n (f) and Y _n (f) can be expressed by the following equations. In this formula, a subscript k-1 is added to indicate that the k-1 is off.
X _nk-1 (f) = A _nk-1 (f) N _k-1 (f) (Equation 5)
Y _nk-1 (f) = B _nk-1 (f) N _k-1 (f) (Equation 6)

From the above equations, by rewriting the noise term X, and Y, the first term on the right side _B 0 of the first term _{A 0 (f) S k (} f) or formula 4 the right side of the equation 3 _{(f) S} k ( If f) is obtained, the spectrum of the sound to be measured can be obtained. At this time, select a time in which the change in noise is small before and after a certain time on. In this way, it can be considered that the on-time noise between the two has not changed. Therefore, X _nk-1 (f) / Y _nk-1 (f) and X _{nk + 1} (f) / Y _{nk + 1} (f) are compared, and the number of times the difference is equal to or less than a predetermined threshold value is selected. That is, assuming that the threshold value is δ _th , the condition is as follows.
| X _{nk + 1} (f) / Y _{nk + 1} (f) -X _nk-1 (f) / Y _nk-1 (f) | ≤δ _th (Equation 7)
After selecting k that satisfies Equation 7, A ₀ (f) _Sk (f) (or B ₀ (f) _Sk (f)) is obtained using Equations 1 to 7.

First, the following equation is obtained from equations 5 and 6.
X _nk-1 (f) / Y _nk-1 (f) = A _nk-1 (f) / B _nk-1 (f) (Equation 8)
Here, since the condition of Equation 7 is selected, the ratio of the noise transfer function at the kth time between the k-1st time and the k + 1th time is the same as the ratio of the noise transfer function at the time of on. Look at it. Further, it is assumed that the noise N itself does not change. From these assumptions and Equation 8, the following equation holds.
X _nk-1 (f) / Y _nk-1 (f) = A _nk (f) _/ B _nk (f) (Equation 9)
N _k-1 (f) = N _k (f) (Equation 10)

Next, from Equations 1 and 2, X ₀ (f) / Y ₀ (f) = A ₀ (f) / B ₀ (f) (Equation 11)
From Equation 3 and Equation 10, N _k-1 (f) = N _k (f)
= (X _nk (f) -A ₀ (f) _Sk (f)) / A _nk (f) (Equation 12)

Next, equations 9, 11 and 12 are substituted into _{B nk} (f) and N _{k (f) of equation 4.} Since the equation becomes long, the notation of (f) representing the frequency is partially omitted.
Y _k = Y ₀ / X ₀ · A <sub>0 Sk
+ Y nk-1 / X nk</sub> -1 · A nk-1 · (X nk -A 0 S k) / A nk ( Formula 13)
With _{A nk-1} ≒ A _n, to organize Formula 13, characteristic spectrum _A 0 calculated by the following formula _{(f) S} k _(f) is obtained.
A ₀ (f) _Sk (f)
= (X ₀ X _nk-1 Y _k- X ₀ Y _nk-1 X _k ) / (X _nk-1 Y _0- X ₀ Y _nk-1 ) (Equation 14)

Since the characteristic spectrum can be expressed using the measurable X _k (f), Y _k (f), X _nk-1 (f), and Y _nk-1 (f) from Equation 14, the sound to be measured by the first microphone 100 The spectrum of can be obtained. If the equations for substituting equations 9, 11 and 12 are changed to equation 3, the characteristic spectra B ₀ (f) and _Sk (f) of the sound to be measured in the second microphone 200 can be obtained in the same manner. ..

The operation of the acoustic characteristic measurement system 1000 of the present embodiment described above is summarized as shown in the flowchart of FIG.

First, the noise is blocked, and the reference spectra of the omnidirectional microphone 100 and the directional microphone 200 of the sound to be measured are acquired (S1). Next, the measurement target sound is turned on / off and the measurement target sound is collected (S2). Next, the sound collection spectrum is calculated by converting the sound collection signal (S3). Next, the times in which the change in noise is small before and after on is selected (S4). Next, the characteristic spectrum of the sound to be measured is calculated using the sound collection spectrum and the reference spectrum of the selected time and the times before and after the selected time (S5). By the above operation, the characteristic spectrum of the sound to be measured can be obtained.

Next, the hardware configuration of the acoustic characteristic measuring device 300 of the present embodiment will be described. FIG. 10 is a block diagram showing a computer 90 that mounts the acoustic characteristic measuring device 300. The computer 90 includes a processor 91, a main storage device 92, an auxiliary storage device 93, an input / output interface 94, and a communication interface 95. In FIG. 10, the interface is abbreviated as I / F (Interface). The processor 91, the main storage device 92, the auxiliary storage device 93, the input / output interface 94, and the communication interface 95 are connected to each other via a bus 99 so as to be capable of data communication. Further, the processor 91, the main storage device 92, the auxiliary storage device 93, and the input / output interface 94 are connected to a network such as the Internet or an intranet via the communication interface 95.

The processor 91 expands the program stored in the auxiliary storage device 93 or the like into the main storage device 92, and executes the expanded program. In the present embodiment, the software program installed in the information processing apparatus 90 may be used. The processor 91 executes the process by the acoustic characteristic measuring device according to the present embodiment.

The main storage device 92 has an area in which the program is developed. The main storage device 92 may be, for example, a volatile memory such as a DRAM (Dynamic Random Access Memory). Further, a non-volatile memory such as MRAM (Magnetoresistive Random Access Memory) may be configured and added as the main storage device 92.

The auxiliary storage device 93 stores various data. The auxiliary storage device 93 is composed of a local disk such as a hard disk or a flash memory. It is also possible to store various data in the main storage device 92 and omit the auxiliary storage device 93.

The input / output interface 94 is an interface for connecting the information processing device 90 and peripheral devices. The communication interface 95 is an interface for connecting to an external system or device through a network such as the Internet or an intranet based on a standard or a specification. The input / output interface 94 and the communication interface 95 may be shared as an interface for connecting to an external device.

The computer 90 may be configured to connect an input device such as a keyboard, a mouse, or a touch panel, if necessary. These input devices are used to input information and settings. When the touch panel is used as an input device, the display screen of the display device may also serve as the interface of the input device. Data communication between the processor 91 and the input device may be mediated by the input / output interface 94.

Further, the computer 90 may be equipped with a display device for displaying information. When a display device is provided, it is preferable that the computer 90 is provided with a display control device (not shown) for controlling the display of the display device. The display device may be connected to the computer 90 via the input / output interface 94.

Further, the information processing apparatus 90 may be provided with a disk drive, if necessary. The disk drive is connected to bus 99. The disk drive mediates between the processor 91 and a recording medium (program recording medium) (not shown), reading a data program from the recording medium, writing the processing result of the information processing apparatus 90 to the recording medium, and the like. The recording medium can be realized by, for example, an optical recording medium such as a CD (Compact Disc) or a DVD (Digital Versaille Disc). Further, the recording medium may be realized by a semiconductor recording medium such as a USB (Universal Serial Bus) memory or an SD (Secure Digital) card, a magnetic recording medium such as a flexible disk, or other recording medium.

The above is an example of the hardware configuration for enabling the acoustic characteristic measuring device according to each embodiment of the present invention. The hardware configuration of FIG. 10 is an example of a hardware configuration for executing arithmetic processing of the acoustic characteristic measuring device according to each embodiment, and does not limit the scope of the present invention. Further, the scope of the present invention also includes a program for causing a computer to execute a process related to the acoustic characteristic measuring device according to each embodiment. Further, a program recording medium on which the program according to each embodiment is recorded is also included in the scope of the present invention.

(Third Embodiment)
In the second embodiment, the first microphone is an omnidirectional microphone and the second microphone is a directional microphone. However, the first microphone and the second microphone do not have to be this combination. For example, they may be the same. FIG. 11 is a schematic diagram showing a signal flow in an acoustic characteristic measuring device using microphones having the same performance as the first microphone and the second microphone. In the present embodiment, instead of using the same microphone for the first microphone and the second microphone, they are separated from each other.

With this configuration, it is assumed that the noise source 600 is located in the upper left of the paper surface in the k-1st measurement when it is off, and moves to the lower left side of the paper surface in the k + 1th measurement. The sound collection spectrum in the k-1th measurement is given by the following equation.
X _nk-1 (f) = A _nk-1 (f) N _k-1 (f) (Equation 15)
Y _nk-1 (f) = B _nk-1 (f) N _k-1 (f) (Equation 16)

The sound collection spectrum in the k + 1th measurement is given by the following equation.
X _{nk + 1} (f) = A _{nk + 1} (f) N _{k + 1} (f) (Equation 17)
Y _{nk + 1} (f) = B _{nk + 1} (f) N _{k + 1} (f) (Equation 18)

In this case, as is clear from FIG. 11, the transfer function ratios A _nk-1 (f) / B _nk-1 (f) and A _{nk + 1} (f) / B _{nk + 1} (f) at the k-1th time are the same. is not it. That is, it becomes as follows.
A _nk-1 (f) / B _nk-1 (f) ≠ A _{nk + 1} (f) / B _{nk + 1} (f) (Equation 19)

On the flip side, if the above ratios are the same, then the noise source is not moving. Then, assuming that the noise N (f) k generated during that period has not changed, the spectrum of the sound to be measured can be calculated in the same manner as in the second embodiment.

Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the structure and details of the present invention within the scope of the present invention.

1,1000 Acoustic characteristic measurement system 10 1st microphone 20 2nd microphone 30 1st sound collection spectrum calculation means 40 2nd sound collection spectrum calculation means 50 Measurement target sound on / off control means 60 Measurement target sound spectrum calculation means 70, 500 Object to be measured 100 1st microphone 200 Directional microphone 300 Acoustic characteristic measuring device 310 1st Fourier conversion processing unit 320 2nd Fourier conversion processing unit 330 Spectrum calculation unit 400 Sound to be measured on / off control device

Claims (9)

The first microphone arranged so as to have a predetermined positional relationship with respect to the position where the measurement object that generates the measurement target sound is arranged,
A second microphone arranged so as to have a predetermined positional relationship with the first microphone,
The measurement target sound on / off control means for turning on / off the measurement target sound at a predetermined cycle, and the measurement target sound on / off control means.
A first sound collection spectrum calculation means for acquiring a first sound collection signal collected by the first microphone and calculating a first sound collection spectrum, and
A second sound collection spectrum calculation means that acquires a second sound collection signal collected by the second microphone and calculates a second sound collection spectrum, and
The first sound collection spectrum and the second sound collection spectrum when the specific time is on, the first sound collection spectrum and the second sound collection spectrum when the sound is off before and after the specific time, and noise are blocked. Based on the first reference spectrum calculated from the first sound collection signal at the time of the operation and the second reference spectrum calculated from the second sound collection signal when the noise is cut off, the first sound at the time of on. A measurement target sound spectrum calculation means for calculating the measurement target sound spectrum by subtracting the noise spectrum from the first sound collection spectrum or the second sound collection spectrum.
An acoustic characteristic measurement system characterized by having. The measurement target sound spectrum calculation means
The ratio between the first sound collection spectrum and the second sound collection spectrum is calculated, and the specific time is selected based on the fact that the difference between the ratios before and after the on time is equal to or less than a predetermined threshold value. The acoustic characteristic measurement system according to claim 1, further comprising a specific time selection means. A first Fourier transform means for calculating the first sound collection spectrum by Fourier transforming the first sound collection signal,
A second Fourier transform means for calculating the second sound collection spectrum by Fourier transforming the second sound collection signal, and
The acoustic characteristic measurement system according to claim 1 or 2. The acoustic characteristic measurement system according to any one of claims 1 to 3, wherein one of the first microphone and the second microphone is an omnidirectional microphone and the other is a directional microphone. It is an acoustic characteristic measurement method for measuring the acoustic characteristics of the sound to be inspected including the noise from the noise source and the sound to be measured generated from the object to be measured.
The object to be measured, the first microphone, and the second microphone are arranged in a predetermined positional relationship.
In an environment where the noise is blocked, the first reference spectrum is calculated from the first sound collection signal in which the first microphone collects the sound to be measured, and the second microphone collects the sound to be measured in the second collection. Calculate the second reference spectrum from the sound signal,
The measurement target sound is turned on / off at a predetermined cycle, the first sound collection signal is acquired to calculate the first sound collection spectrum, and the second sound collection signal is acquired to calculate the second sound collection spectrum. ,
The first sound collection spectrum and the second sound collection spectrum when the specific time is on, the first sound collection spectrum and the second sound collection spectrum when the sound is off before and after the specific time, and the first sound collection spectrum. Based on the reference spectrum and the second reference spectrum, the spectrum of the sound to be measured is calculated by subtracting the noise spectrum from the first sound collection spectrum or the second sound collection spectrum at the time of on. A method for measuring acoustic characteristics. The ratio between the first sound collection spectrum and the second sound collection spectrum is calculated, and the specific time is selected based on the fact that the difference between the ratios before and after the on time is equal to or less than a predetermined threshold value. The method for measuring acoustic characteristics according to claim 5, wherein the method is to be used. The first sound collection signal is Fourier transformed to calculate the first sound collection spectrum.
The second sound collection signal is Fourier transformed to calculate the second sound collection spectrum.
The method for measuring acoustic characteristics according to claim 5 or 6. The method for measuring acoustic characteristics according to any one of claims 5 to 7, wherein one of the first microphone and the second microphone is an omnidirectional microphone and the other is a directional microphone. It is an acoustic characteristic measurement program for measuring the acoustic characteristics of the sound to be inspected including the noise from the noise source and the sound to be measured generated from the object to be measured.
With the measurement object, the omnidirectional first microphone, and the directional second microphone arranged in a predetermined positional relationship,
In an environment where the noise is blocked, a process of calculating the first reference spectrum from the first sound collection signal in which the first microphone collects the measurement target sound, and a second microphone in which the measurement target sound is collected. The process of calculating the second reference spectrum from the two sound collection signals and
Control is performed to turn on / off the measurement target sound at a predetermined cycle, the process of acquiring the first sound collection signal to calculate the first sound collection spectrum, and the process of acquiring the war record second sound collection signal and collecting the second sound. The process of calculating the sound spectrum and
The first sound collection spectrum and the second sound collection spectrum when the specific time is on, the first sound collection spectrum and the second sound collection spectrum when the sound is off before and after the specific time, and the first sound collection spectrum. Based on the reference spectrum and the second reference spectrum, the spectrum of the sound to be measured is calculated by subtracting the noise spectrum from the first sound collection spectrum or the second sound collection spectrum at the time of on. Processing and
An acoustic characteristic measurement program characterized by having a computer execute the above.

Images