JP7722210B2 - Noise evaluation device, acoustic evaluation device, noise evaluation method, acoustic evaluation method, noise evaluation program, and acoustic evaluation program - Google Patents

Description

The present invention relates to a noise evaluation device, etc.

Generally, electrical products are made up of multiple modules, including electronic components, mechanical components, and housings. When manufacturing such electrical products, the modules are assembled in order, and then functional and visual inspections are conducted to confirm that there are no problems, and the assembly is then complete.

One of these functional tests is a sound test. This checks, for example, whether the device's operation sounds and warning sounds are sounding correctly and whether there are any problems with the audio quality. In such sound tests, the collected sounds can sometimes include noise from the surrounding environment, leading to erroneous judgments. For this reason, it is common to perform tests with soundproofing measures in place, such as storing the product in a highly soundproof box known as a soundproof box.

However, with the above-mentioned method using a soundproof box, it is necessary to remove the inspected product from the box and store the next product back in the box after each inspection. This makes the inspection time longer and the inspection process more complicated. As a result, efforts are being made to collect sound without using soundproofing measures such as a soundproof box, and then remove noise through signal processing before conducting the inspection. In this case, technology is needed to distinguish whether the collected sound is from the target object or noise from the surrounding environment, and then remove the noise.

For example, Patent Document 1 discloses an invention for a voice recognition device that performs voice recognition by removing noise from the surrounding environment. This voice recognition device first samples ambient noise (noise) without voice (sound to be measured), and converts the distribution of the time components of the ambient noise into a distribution (spectrum) of frequency components using FFT (Fast Fourier Transform). Next, voice including the ambient noise is sampled, and the distribution of the time components of the voice is converted into a distribution of frequency components using FFT. Then, by subtracting the frequency components of the noise from the frequency components of the voice, the frequency components of only the voice can be obtained. Related technology is also disclosed in Patent Document 2.

Japanese Patent Application Laid-Open No. 2003-005788 Japanese Patent Application Laid-Open No. 2004-271596

Patent Document 1, mentioned above, assumes that noise does not change over time. In other words, if the noise is the same when sampling the ambient environmental sound and when sampling the sound to be measured (audio), it is possible to accurately extract the frequency components of only the sound to be measured. However, if the noise changes between the two sampling periods, there is a problem in that different frequency components of the noise than actually exist are subtracted from the frequency components of the audio. The reason for this is that, even though it is not possible to accurately estimate the noise components when the noise is changing, the noise components sampled under the assumption that they do not change are used.

The present invention was made in consideration of the above problems, and aims to provide a noise evaluation device etc. that enables more accurate estimation of the target sound when noise other than the target sound fluctuates.

To solve the above problem, the noise evaluation device of the present invention includes a measurement target sound on/off control unit that repeatedly turns on/off the output of the measurement target sound, which is sound emitted by the measurement target, as on/off control, and a collection unit that acquires a collected sound signal, which is a signal obtained by converting sound including the measurement target sound into an electrical signal. The device includes a sound signal acquisition unit, a sound collection signal extraction unit that extracts from the sound collection signal, based on the on/off control, the sound collection signal when the output of the sound to be measured is turned on as a first sound collection signal for that time, and the sound collection signal when the output of the sound to be measured is turned off as a second sound collection signal for that time, and a frequency spectrum generation unit that converts the first sound collection signal for each time into a frequency spectrum to generate a plurality of first frequency spectra, and converts the second sound collection signal for each time into a frequency spectrum to generate a plurality of second frequency spectra, a fluctuation range determination unit that determines whether the fluctuation range of the frequency component of each of the plurality of second frequency spectra over a predetermined period is greater than or equal to a predetermined threshold value or less than the threshold value, and a noise frequency spectrum estimation unit that estimates the frequency spectrum of noise included in the plurality of first frequency spectra as a noise frequency spectrum based on the plurality of first frequency spectra, the plurality of second frequency spectra, and the determination result of the fluctuation range determination unit.

The acoustic evaluation device of the present invention also includes the noise evaluation device described above and a measurement target sound frequency spectrum estimation unit that estimates a measurement target sound frequency spectrum, which is the frequency spectrum of the measurement target sound, based on the first frequency spectrum and the noise frequency spectrum.

In addition, in the noise evaluation method of the present invention, a computer controls the repeated on/off switching of a measurement target sound, acquires a sound including the measurement target sound as a sound collection signal, and, based on the control, divides the sound collection signal by designating the sound collection signal when the measurement target sound is turned on as a first sound collection signal for that time and the sound collection signal when the measurement target sound is turned off as a second sound collection signal for that time, converting the first sound collection signal for each time into a frequency spectrum to generate a first frequency spectrum, and converting the second sound collection signal for each time into a frequency spectrum to generate a second frequency spectrum, determining whether the fluctuation range of each frequency component of the second frequency spectrum over a predetermined period is greater than or equal to a predetermined threshold value or less than the threshold value, and estimating a noise frequency spectrum based on the first frequency spectrum, the second frequency spectrum, and the determination result of the fluctuation range.

In addition, in the acoustic evaluation method of the present invention, a computer estimates the noise frequency spectrum using the above-mentioned noise evaluation method, and estimates a measurement target sound frequency spectrum, which is the frequency spectrum of the measurement target sound, based on the first frequency spectrum and the noise frequency spectrum.

The noise evaluation program of the present invention causes a computer to execute the following processes: a process for controlling the repeated on/off of a measurement target sound; a process for acquiring a sound including the measurement target sound as a sound collection signal; a process for dividing the sound collection signal based on the control, by designating the sound collection signal when the measurement target sound is turned on as a first sound collection signal for that time and the sound collection signal when the measurement target sound is turned off as a second sound collection signal for that time; a process for converting the first sound collection signal for each time into a frequency spectrum to generate a first frequency spectrum, and a process for converting the second sound collection signal for each time into a frequency spectrum to generate a second frequency spectrum; a process for determining whether the fluctuation range of each frequency component of the second frequency spectrum over a predetermined period is greater than or equal to a predetermined threshold value or less than the threshold value; and a process for estimating a noise frequency spectrum based on the first frequency spectrum, the second frequency spectrum, and the determination result of the fluctuation range.

The acoustic evaluation program of the present invention also causes a computer to execute the above-mentioned noise evaluation program and estimate a measurement target sound frequency spectrum, which is the frequency spectrum of the measurement target sound, based on the first frequency spectrum and the noise frequency spectrum.

The effect of the present invention is to provide a noise evaluation device that enables more accurate estimation of the target sound when noise other than the target sound contained in the collected sound signal fluctuates.

1 is a block diagram showing a noise evaluation device according to a first embodiment; 4 is a timing chart showing the relationship between an on/off control signal and a collected sound signal in the first embodiment. 4 is a flowchart showing the operation of the noise evaluation device of the first embodiment. 10 is a flowchart showing a specific example 1 of the operation of the noise frequency spectrum estimating unit of the noise evaluation apparatus of the first embodiment. 4 is a graph showing specific examples of a first frequency spectrum and a second frequency spectrum according to the first embodiment. 10 is a flowchart illustrating a specific example 2 of the operation of the noise frequency spectrum estimating unit of the noise evaluation apparatus according to the first embodiment. 1 is a block diagram showing a sound evaluation device according to a first embodiment; 4 is a flowchart showing the operation of the sound evaluation device of the first embodiment. 4 is a flowchart showing a first operation example of the sound evaluation device according to the first embodiment. 10 is a flowchart showing a second operation example of the sound evaluation device according to the first embodiment.

Embodiments of the present invention will be described in detail below with reference to the drawings. However, while the embodiments described below have technically preferable limitations for implementing the present invention, they do not limit the scope of the invention. Note that similar components in each drawing are given the same numbers, and descriptions may be omitted.

(First embodiment)
1 is a block diagram showing a noise evaluation device 100 according to the first embodiment. The noise evaluation device 100 includes a measurement target sound on/off control unit 110, a collected sound signal acquisition unit 120, a collected sound signal extraction unit 130, a frequency spectrum generation unit 140, a fluctuation range determination unit 150, and a noise frequency spectrum estimating unit 160. The noise evaluation device 100 can be configured, for example, by a computer equipped with a processor, a memory, an input/output interface, a storage device, etc.

The measurement target sound on/off control unit 110 performs on/off control. Here, on/off control refers to repeatedly turning on and off the output of the measurement target sound, which is the sound emitted by the measurement target 200. Figure 2 is a timing chart showing the relationship between the on/off control signal and the collected sound signal in the first embodiment.

The sound collection signal acquisition unit 120 acquires a sound collection signal, which is a signal obtained by converting sound including the sound to be measured into an electrical signal. The sound collection signal is, for example, an electrical signal generated by the sound collection microphone 300 collecting sound including the sound to be measured. As shown in FIG. 2, the sound to be measured is output in synchronization with the on/off control signal being on, and a first sound collection signal is acquired via the sound collection microphone 300. When the on/off control signal is off, no sound to be measured is output, and noise generated around the sound collection microphone 300 is acquired. This noise signal becomes the second sound collection signal. As shown in FIG. 2, the first sound collection signal and the second sound collection signal are acquired alternately. The example in FIG. 2 shows that the first sound collection signal at the (i-1)th time, the second sound collection signal at the (i-1)th time, the first sound collection signal at the (i-1)th time, the second sound collection signal at the (i)th time, and so on are repeated.

Based on the on/off control, the sound collection signal extraction unit 130 extracts from the sound collection signal the sound collection signal when the output of the sound to be measured is turned on as the first sound collection signal for that time, and the sound collection signal when the sound to be measured is turned off as the second sound collection signal for that time.

The frequency spectrum generation unit 140 converts the first collected sound signal for each time into a frequency spectrum to generate multiple first frequency spectra, and converts the second collected sound signal for each time into a frequency spectrum to generate multiple second frequency spectra. The first frequency spectrum can be generated, for example, by performing a fast Fourier transform (FFT) on the first collected sound signal for the target time. Similarly, the second frequency spectrum can be generated by performing a fast Fourier transform on the second collected sound signal for the target time.

The fluctuation range determination unit 150 determines whether the fluctuation range of each frequency component of multiple second frequency spectra over a predetermined period of time is greater than or equal to a predetermined threshold value or less than the threshold value. The predetermined period can be determined, for example, to include the number of on/off cycles for which statistics are valid. A specific number can be, for example, between 10 and 1000, but is not limited to this. The fluctuation range can also be expressed, for example, as the standard deviation of sound pressure. Alternatively, it can be expressed as a range that is the difference between maximum and minimum sound pressure. The threshold value can be determined based on the standard deviation or range depending on the environment. Specifically, for example, the threshold value can be determined by conducting a preliminary experiment in which data is acquired by intentionally creating a state where noise fluctuations are small and a state where noise fluctuations are large.

The noise frequency spectrum estimation unit 160 estimates the frequency spectrum of noise contained in the multiple first frequency spectra as the noise frequency spectrum. The noise frequency spectrum is estimated based on the multiple first frequency spectra, multiple second frequency spectra, and the determination result of the fluctuation range determination unit.

Next, the operation of the noise evaluation device 100 will be described. Figure 3 is a flowchart showing the operation of the noise evaluation device 100 of the first embodiment. First, the measurement target sound on/off control unit 110 controls the measurement target 200 to repeatedly turn on and off the output of the measurement target sound (S1). Next, the sound collection signal acquisition unit 120 acquires a signal obtained by converting sound including the measurement target sound into an electrical signal as a collection signal (S2). Next, based on the on/off control of the sound collection signal, the sound collection signal extraction unit 130 extracts from the collection signal the sound collection signal when the output of the measurement target sound is turned on as a first collection signal and the sound collection signal when the output of the measurement target sound is turned off as a second collection signal (S3). Next, the frequency spectrum generation unit 140 generates multiple first frequency spectra by converting the first collection signal for each time into a frequency spectrum. Furthermore, the frequency spectrum generation unit 140 generates multiple second frequency spectra by converting the second collection signal for each time into a frequency spectrum (S4). Next, the fluctuation range determination unit 150 determines whether the fluctuation range of each frequency component of the multiple second frequency spectra over a predetermined period is greater than or equal to a predetermined threshold value or less than the threshold value (S5).Then, the noise frequency spectrum estimation unit 160 estimates the noise frequency spectrum based on the first frequency spectrum, the second frequency spectrum, and the determination result of the fluctuation range determination unit 150 (S6).

The second sound collection signal described above is the sound collection signal when the measurement target sound is off. In other words, the second sound collection signal is noise other than the measurement target sound. If this noise does not change, the measurement target sound can be extracted by subtracting the second sound collection signal when the measurement target sound is off from the first sound collection signal when the measurement target sound is on, as in the method described in Patent Document 1. However, if the noise is changing, the same method cannot accurately estimate the noise, and erroneous noise will be subtracted. For this reason, this method cannot accurately estimate the measurement target sound. On the other hand, the noise evaluation device 100 of this embodiment matches the noise estimation method to the fluctuation range of the noise (frequency components of the second frequency spectrum), allowing for more accurate estimation of the measurement target sound. A specific estimation method is described below.

(Specific Example 1)
Fig. 4 is a flowchart showing a first specific example of the operation of the noise frequency spectrum estimator of the noise evaluation apparatus of the first embodiment. The processing in the flowchart in Fig. 4 corresponds to details of the processing in S6 in the flowchart in Fig. 3. In other words, the processing in the flowchart in Fig. 4 is processing performed after the processing in S1 to S5 in Fig. 3 is completed.

First, the noise frequency spectrum estimating unit 160 acquires a plurality of second frequency spectra over a predetermined period (S611). Next, the noise frequency spectrum estimating unit 160 acquires a determination result of the fluctuation range for each frequency component of the plurality of second frequency spectra. Then, the noise frequency spectrum estimating unit 160 performs a loop process L1 in which each frequency component of the noise frequency spectrum is set (S612-S616). The loop process L1 is performed until calculation of all frequency components f _k (k = 1 to M) of the noise frequency spectrum within the predetermined target frequency range is completed. Here, the sound pressure of the frequency component f _k in the i-th first frequency spectrum is P _oni (f _k ), the sound pressure of the frequency component f _k in the i-th second frequency spectrum is P _offi (f _k ), and the threshold is P _th . The sound pressure of the frequency component f _k in the noise frequency spectrum is denoted as N(f _k ).

In loop processing L1, the noise frequency spectrum estimating unit 160 first obtains the fluctuation range for frequency components f _k in multiple second frequency spectra within a predetermined target period (S613). Next, the noise frequency spectrum estimating unit 160 determines whether the fluctuation range of frequency component f _k is less than a threshold P _th (S614). If the fluctuation range is less than the threshold P _th (Yes in S614), the noise frequency spectrum estimating unit 160 sets the average value of the frequency component P _off (f _k ) in the second frequency spectrum to the frequency component N(f _k ) in the noise frequency spectrum (S615). On the other hand, if the fluctuation range is equal to or greater than the threshold P _th (No in S614), the noise frequency spectrum estimating unit 160 sets the minimum value P _offmin (f _k ) in the target range to the frequency component N(f _k ) in the noise frequency spectrum (S616). Through the above operations, the noise frequency spectrum estimator 160 determines all target frequency components and estimates the noise frequency spectrum. This operation is based on the judgment that the sound pressure is stable for noise frequency components whose fluctuation range is smaller than the threshold. On the other hand, for noise frequency components whose fluctuation range is large, the minimum value is used to reduce the influence of sudden noise occurrence.

Next, we will explain a calculation example for estimating a specific noise frequency spectrum. Figure 5 is a graph showing specific examples of the first frequency spectrum and second frequency spectrum of the first embodiment. Figures 5(a), (b), and (c) show the first frequency spectrum for the first, second, and third measurements. Figures 5(d), (e), and (f) show the second frequency spectrum for the first, second, and third measurements.

5(d), (e), and (f), for the second frequency spectrum frequency component _f1 , _Poff1 ( _f1 ), _Poff2 ( _f1 ), and _Poff3 ( _f1 ) are all 0 and the fluctuation range is less than the threshold _Pth . For the frequency component f2, _Poff1 ( _f2 ), _Poff2 ( _f2 ), and _Poff3 ( _f2 ) are constant and the fluctuation range is less than the threshold _Pth . For the frequency component _f3 , _Poff1 ( _f3 ), _Poff2 ( _f3 ), and _Poff3 ( _f3 ) fluctuate and the fluctuation range is _Poff2 ( _f3 ) _-Poff1 ( _f3 ). Also, it is assumed that P _off2 (f ₃ ) - P _off2 (f ₃ ) ≥ P _th .

From the above, the average value is used for the frequency components f ₁ and f ₂ , and the minimum value is used for f _3. As a result, each frequency component of the noise frequency spectrum is calculated using the following formula.
N(f ₁ )={P _off1 (f ₁ )+P _off2 (f ₁ )+P _off3 (f ₁ )}/3 (Formula 1)
N(f ₂ )={P _off1 (f ₂ )+P _off2 (f ₂ )+P _off3 (f ₂ )}/3 (Formula 2)
N(f ₃ )=P _off3 (f ₁ ) (Equation 3)
By performing the above operation, the influence of large noise that occurs suddenly can be reduced, and a more accurate estimation of the noise frequency spectrum becomes possible.

(Specific Example 2)
Fig. 6 is a flowchart showing a second specific example of the operation of the noise frequency spectrum estimator of the noise evaluation apparatus according to the first embodiment. The processing in the flowchart of Fig. 6 corresponds to details of the processing in S6 in the flowchart of Fig. 3, similar to the flowchart of Fig. 4. In other words, the processing in the flowchart of Fig. 6 is processing performed after the processing in S1 to S5 in Fig. 3 is completed.

The operation of Specific Example 2 differs from that of Specific Example 1 in that the median value is used for frequency components with a small fluctuation range. In other words, the processing of S621 to S624 and S626 in the flowchart of FIG. 6 is the same as the processing of S611 to S614 and S616 in the flowchart of FIG. 4. Only S625 differs from S615.

The operation of the flowchart in Fig. 6 will be described below. First, the noise frequency spectrum estimating unit 160 acquires a plurality of second frequency spectra over a predetermined period (S621). Next, the noise frequency spectrum estimating unit 160 acquires the determination results of the fluctuation range for each frequency component of the plurality of second frequency spectra. Then, the noise frequency spectrum estimating unit 160 performs loop processing L2 to set each frequency component of the noise frequency spectrum (S622-S626). Loop processing L2 is performed until calculation of all frequency components f _k (k = 1 to M) of the noise frequency spectrum within the predetermined target frequency range is completed.

In loop processing L2, the noise frequency spectrum estimating unit 160 first obtains the fluctuation range for frequency components f _k in multiple second frequency spectra within a predetermined target period (S623). Next, the noise frequency spectrum estimating unit 160 determines whether the fluctuation range of frequency component f _k is less than threshold P _th (S624). If the fluctuation range is less than threshold P _th (Yes in S624), the noise frequency spectrum estimating unit 160 sets the median value of the frequency component P _off (f _k ) in the second frequency spectrum to the frequency component N(f _k ) in the noise frequency spectrum (S625). On the other hand, if the fluctuation range is equal to or greater than threshold P _th (No in S624), the noise frequency spectrum estimating unit 160 sets the minimum value P _offmin (f _k ) in the target range to the frequency component N(f _k ) in the noise frequency spectrum (S626). Through the above operations, the noise frequency spectrum estimator 160 determines all target frequency components and estimates the noise frequency spectrum. This operation is based on the judgment that the sound pressure is stable for noise frequency components whose fluctuation range is smaller than the threshold. On the other hand, for noise frequency components whose fluctuation range is large, the minimum value is used to reduce the influence of sudden noise occurrence.

Next, as in Example 1, an example of calculating a noise frequency spectrum will be described. Here, the specific examples of the first and second frequency spectra in FIG. 5 are used in calculating the noise frequency spectrum. As described above, for frequency components _f1 and _f2 , the fluctuation range of the frequency components of the second frequency spectrum is less than the threshold _Pth . Therefore, the median value is adopted. On the other hand, for frequency component _f3 , the fluctuation range of the second frequency spectrum is equal to or greater than the threshold _Pth . Therefore, the minimum value is adopted.

From the above, each frequency component of the noise frequency spectrum is calculated using the following formula:
N(f ₁ )=median of P _offi (f ₁ ) (Equation 4)
N(f ₂ )=median of P _offi (f ₂ ) (Equation 5)
N(f ₃ )=P _off3 (f ₁ ) (Formula 6)
As described above, the noise evaluation apparatus 100 of this embodiment can reduce the influence of noise fluctuations and estimate the noise frequency spectrum more accurately.

Next, we will explain the sound evaluation device 1000 that uses the noise evaluation device 100. Figure 7 is a block diagram showing the sound evaluation device of the first embodiment. The sound evaluation device 1000 has the noise evaluation device 100 and a measurement target sound frequency spectrum estimation unit 400. The measurement target sound frequency spectrum estimation unit 400 estimates the measurement target sound frequency spectrum, which is the frequency spectrum of the measurement target sound, based on the first frequency spectrum and the noise frequency spectrum.

Figure 8 is a flowchart showing the operation of the sound evaluation device 1000 of the first embodiment. First, the noise evaluation device 100 estimates the noise frequency spectrum (S101). Next, the measurement target sound frequency spectrum estimation unit 400 estimates the measurement target sound frequency spectrum based on multiple first frequency spectra over a predetermined period and the estimated noise frequency spectrum (S102).

Next, we will explain the specific method for estimating the frequency spectrum of the sound to be measured.

(Specific Example 3)
9 is a flowchart showing a first operation example of the acoustic evaluation device of the first embodiment. First, the noise evaluation device 100 estimates a noise frequency spectrum (S101). Next, the measurement-target sound frequency spectrum estimation unit 400 calculates the average value of the first frequency spectrum (S102). Next, the measurement-target sound frequency spectrum estimation unit 400 estimates the measurement-target sound frequency spectrum by subtracting the estimated noise frequency spectrum from the average value of the first frequency spectrum (S103).

The above operations reduce the influence of noise fluctuations on noise frequency components with large fluctuation ranges, enabling more accurate estimation of the sound frequency spectrum to be measured.

(Specific Example 4)
Next, a method for estimating the measurement target sound frequency spectrum without performing noise estimation for frequency components with a large fluctuation range in the second frequency spectrum will be described.

Figure 10 is a flowchart showing a second operation example of the acoustic evaluation device of the first embodiment. First, the noise evaluation device 100 estimates the noise frequency spectrum (S201). Next, the measurement target sound frequency spectrum estimation unit 400 calculates the average value of the first frequency spectrum (S202). Next, the measurement target sound frequency spectrum estimation unit 400 calculates the preliminary measurement target sound frequency spectrum by subtracting the estimated noise frequency spectrum from the average value of the first frequency spectrum (S203). Up to this point, this is the same as in Specific Example 3. Next, the measurement target sound frequency spectrum estimation unit 400 replaces frequency components of the preliminary measurement target sound frequency spectrum that have a large fluctuation range in the second frequency spectrum with the minimum value of the first frequency spectrum, thereby estimating the measurement target sound frequency spectrum (S204). In the above operation, noise frequency spectrum estimation is not performed for frequency components that have a large fluctuation range in the second frequency spectrum. Then, for that frequency component, the measurement target sound frequency spectrum estimation unit 400 sets the smallest value among the frequency components of the multiple first frequency spectra as the frequency component of the measurement target sound frequency spectrum. Measurement object 200 basically repeatedly outputs the same sound. Meanwhile, the first frequency spectrum is the sum of the measurement target frequency spectrum and the noise frequency spectrum. For this reason, for frequency components with large fluctuations in the first frequency spectrum, those with high sound pressure are estimated to contain a large proportion of noise, and those with low sound pressure are estimated to contain a small proportion of noise. Therefore, for that frequency component, it is thought that the measurement target sound frequency spectrum estimation unit 400 can more accurately estimate the measurement target sound frequency spectrum by using the first frequency spectrum with the smallest sound pressure.

When the above operation is applied to the data in FIG. 5, the frequency component S(fk) of the frequency fk of the measurement target sound frequency spectrum can be estimated by the following equation.
S(f ₁ )={P _on1 (f ₁ )+P _on2 (f ₁ )+P _on3 (f ₁ )}/3
-{P _off1 (f ₁ )+P _off2 (f ₁ )+P _off3 (f ₁ )}/3 (Formula 7)
S(f ₂ )={P _on1 (f ₂ )+P _on2 (f ₂ )+P _on3 (f ₂ )}/3
-{P _off1 (f ₂ )+P _off2 (f ₂ )+P _off3 (f ₂ )}/3 (Formula 8)
S(f ₃ )=P _on2 (f ₃ ) (Formula 9)
As described above, the sound evaluation device 1000 of this embodiment can reduce the influence of noise with large fluctuations and estimate the measurement target sound more accurately.

The noise evaluation device and other components of this embodiment have been described above.

The noise evaluation device 100 of this embodiment has a measurement target sound on/off control unit 110, a sound collection signal acquisition unit 120, a sound collection signal extraction unit 130, a frequency spectrum generation unit 140, a fluctuation range determination unit 150, and a noise frequency spectrum estimation unit 160. The measurement target sound on/off control unit 110 performs on/off control to repeatedly turn on/off the output of the measurement target sound, which is sound emitted by the measurement target. The sound collection signal acquisition unit 120 acquires a sound collection signal, which is a signal obtained by converting sound including the measurement target sound into an electrical signal. Based on the on/off control, the sound collection signal extraction unit 130 extracts from the sound collection signal the sound collection signal when the output of the measurement target sound is turned on as the first sound collection signal for that time, and the sound collection signal when the output of the measurement target sound is turned off as the second sound collection signal for that time. By extracting the sound collection signal in synchronization with the on/off control, it is possible to separate and extract the first sound collection signal for the on-time and the second sound collection signal for the off-time. The frequency spectrum generation unit 140 converts the first sound collection signal for each time into a frequency spectrum to generate multiple first frequency spectra, and converts the second sound collection signal for each time into a frequency spectrum to generate multiple second frequency spectra. Through this operation, the frequency spectrum generation unit 140 can generate the first frequency spectrum and the second frequency spectrum for each on/off time. The fluctuation range determination unit 150 determines whether the fluctuation range of each frequency component of the multiple second frequency spectra over a predetermined period is greater than or equal to a predetermined threshold value or less than a predetermined threshold value. Through this operation, the fluctuation range determination unit 150 can determine whether the fluctuation range of each frequency component of the second frequency spectrum is large or small. The noise frequency spectrum estimation unit 160 estimates the frequency spectrum of noise contained in the multiple first frequency spectra as the noise frequency spectrum based on the multiple first frequency spectra, the multiple second frequency spectra, and the determination result of the fluctuation range determination unit. Through this operation, the noise frequency spectrum estimation unit 160 can reduce the influence of fluctuations on frequency components of noise with large fluctuations and more accurately estimate the noise frequency spectrum.

According to another aspect, the noise frequency spectrum estimation unit 160 of the noise evaluation device 100 estimates the noise frequency spectrum. For frequency components of the second frequency spectrum whose fluctuation range is less than a threshold, the noise frequency spectrum estimation unit 160 sets the average value of each frequency component of the second frequency spectrum over a predetermined period as the frequency component of the noise frequency spectrum. Furthermore, for frequency components of the second frequency spectrum whose fluctuation range is equal to or greater than the threshold, the noise frequency spectrum estimation unit 160 sets the minimum value of the frequency components of the second frequency spectrum over a predetermined period as the frequency component of the noise frequency spectrum. Through these operations, the noise frequency spectrum estimation unit 160 can estimate the noise frequency spectrum while reducing the influence of fluctuations for frequency components of noise with large fluctuations.

Also, according to one aspect, the noise frequency spectrum estimation unit 160 of the noise evaluation device 100 estimates the noise frequency spectrum. For frequency components of the second frequency spectrum whose fluctuation range is less than a threshold, the noise frequency spectrum estimation unit 160 sets the median value of each frequency component of the second frequency spectrum over a predetermined period as the frequency component of the noise frequency spectrum. Furthermore, for frequency components of the second frequency spectrum whose fluctuation range is equal to or greater than the threshold, the noise frequency spectrum estimation unit 160 sets the minimum value of the frequency components of the second frequency spectrum over a predetermined period as the frequency component of the noise frequency spectrum. By using the median value, the noise frequency spectrum estimation unit 160 can estimate more likely frequency component values for frequency components of the second frequency spectrum that have a small number of outlying values.

The sound evaluation device 1000 of this embodiment also includes any one of the noise evaluation devices 100 described above and a measurement target sound frequency spectrum estimation unit 400. The measurement target sound frequency spectrum estimation unit 400 estimates the measurement target sound frequency spectrum, which is the frequency spectrum of the measurement target sound, based on the first frequency spectrum and the noise frequency spectrum. As described above, the noise evaluation device 100 can estimate the noise frequency spectrum more accurately. The measurement target sound frequency spectrum estimation unit 400 estimates the measurement target sound frequency spectrum based on this noise frequency spectrum. Therefore, the sound evaluation device 1000 can reduce the influence of noise fluctuations and more accurately estimate the measurement target sound frequency spectrum.

According to another aspect, the measurement target sound frequency spectrum estimation unit 400 of the acoustic evaluation device 1000 estimates the measurement target sound frequency spectrum for a predetermined period. In doing so, the measurement target sound frequency spectrum estimation unit 400 estimates the measurement target sound frequency spectrum by subtracting each frequency component of the noise frequency spectrum from each frequency component of the average value of the frequency components of the first frequency spectrum. This operation reduces the influence of fluctuations in frequency components of the noise frequency spectrum that fluctuate greatly, allowing the measurement target sound frequency spectrum estimation unit 400 to more accurately estimate the measurement target sound frequency spectrum.

According to one aspect, the measurement target sound frequency spectrum estimation unit 400 of the acoustic evaluation device 1000 calculates the average value of each frequency component of the second frequency spectrum over a predetermined period for frequency components of the second frequency spectrum whose fluctuation range is less than a threshold. The measurement target sound frequency spectrum estimation unit 400 also determines the frequency components of the measurement target sound frequency spectrum by subtracting the average value of each frequency component of the second frequency spectrum from the average value of each frequency component of the first frequency spectrum. Furthermore, for frequency components of the second frequency spectrum whose fluctuation range is equal to or greater than a threshold, the minimum value of each frequency component of the first frequency spectrum over a predetermined period is determined as the frequency components of the measurement target sound frequency spectrum. By adopting the minimum value of the frequency components of the first frequency spectrum over a predetermined period, it is possible to set frequency components of the measurement target sound frequency spectrum that are estimated to contain few noise components.

In addition, in the noise evaluation method of this embodiment, a computer performs on/off control to repeatedly turn on/off the output of the measurement target sound, which is sound emitted by the measurement target. The computer also acquires a sound collection signal, which is a signal obtained by converting sound including the measurement target sound into an electrical signal. Based on the on/off control, the computer extracts from the sound collection signal the sound collection signal when the output of the measurement target sound is turned on as the first sound collection signal for that time, and the sound collection signal when the output of the measurement target sound is turned off as the second sound collection signal for that time. By extracting the sound collection signal in synchronization with the on/off control, the computer can separate and extract the first sound collection signal when the output of the measurement target sound is turned on and the second sound collection signal when the output of the measurement target sound is turned off. The computer also converts the first sound collection signal for each time into a frequency spectrum to generate multiple first frequency spectra, and converts the second sound collection signal for each time into a frequency spectrum to generate multiple second frequency spectra. This operation allows the computer to generate a first frequency spectrum and a second frequency spectrum for each on/off time. The computer also determines whether the fluctuation range of each frequency component of the multiple second frequency spectra over a predetermined period is greater than or equal to a predetermined threshold value or less than the threshold value. Through this operation, the computer can determine whether the fluctuation range of each frequency component of the second frequency spectrum is large or small. The computer also estimates the frequency spectrum of noise contained in the multiple first frequency spectra as a noise frequency spectrum based on the multiple first frequency spectra, the multiple second frequency spectra, and the determination result of the fluctuation range determination unit. Through this operation, the computer can reduce the influence of fluctuations on frequency components of noise with large fluctuations and more accurately estimate the noise frequency spectrum.

In addition, in the acoustic evaluation method of this embodiment, the computer estimates the noise frequency spectrum using the noise evaluation method described above, and estimates the measurement target sound frequency spectrum, which is the frequency spectrum of the measurement target sound, based on the first frequency spectrum and the noise frequency spectrum. This operation allows the computer to more accurately estimate the noise frequency spectrum, even for frequency components with large fluctuations. As a result, the computer can more accurately estimate the measurement target sound frequency spectrum.

The noise evaluation program of this embodiment also causes a computer to execute a process for performing on/off control to repeatedly turn on/off the output of the measurement target sound, which is sound emitted by the measurement target. The noise evaluation program also causes a computer to execute a process for acquiring a sound collection signal, which is a signal obtained by converting sound including the measurement target sound into an electrical signal. The noise evaluation program also causes the computer to execute a process for converting the sound collection signal when the output of the measurement target sound is turned on based on the on/off control as the first sound collection signal for that time. The noise evaluation program also causes the computer to execute a process for extracting the sound collection signal when the output of the measurement target sound is turned off from the sound collection signal as the second sound collection signal for that time. By extracting the sound collection signal in synchronization with the on/off control, the computer can separate and extract the first sound collection signal when the output was turned on and the second sound collection signal when the output was turned off. The noise evaluation program also causes the computer to execute a process for converting the first sound collection signal for each time into a frequency spectrum to generate multiple first frequency spectra, and converting the second sound collection signal for each time into a frequency spectrum to generate multiple second frequency spectra. This operation allows the computer to generate a first frequency spectrum and a second frequency spectrum for each on/off cycle. The noise evaluation program also causes the computer to execute a process to determine whether the fluctuation range of each frequency component of multiple second frequency spectra over a predetermined period is greater than or equal to a predetermined threshold or less than the threshold. This operation allows the computer to determine whether the fluctuation range of each frequency component of the second frequency spectrum is large or small. The noise evaluation program also causes the computer to execute a process to estimate a noise frequency spectrum. The computer estimates the frequency spectrum of noise contained in the multiple first frequency spectra as the noise frequency spectrum based on the multiple first frequency spectra, the multiple second frequency spectra, and the determination result of the fluctuation range determination unit. This operation allows the computer to reduce the influence of fluctuations in frequency components of noise with large fluctuations and more accurately estimate the noise frequency spectrum.

The acoustic evaluation program of this embodiment also causes a computer to execute the process of running the noise evaluation program described above. It also causes the computer to execute a process of estimating a measurement target sound frequency spectrum, which is the frequency spectrum of the measurement target sound, based on the first frequency spectrum and the noise frequency spectrum. This operation allows the computer to more accurately estimate the noise frequency spectrum, even for frequency components with large fluctuations. Therefore, the computer can more accurately estimate the measurement target sound frequency spectrum.

The scope of the present invention also includes a program that causes a computer to execute the processing of the first embodiment described above, and a recording medium on which the program is stored. Examples of recording media that can be used include magnetic disks, magnetic tapes, optical disks, magneto-optical disks, and semiconductor memories.

The present invention has been described above using the above-mentioned embodiment as an exemplary example. However, the present invention is not limited to the above-mentioned embodiment. In other words, the present invention can be applied in various aspects that are understandable to those skilled in the art within the scope of the present invention.

REFERENCE SIGNS LIST 100 Noise evaluation device 110 Measurement target sound on/off control unit 120 Sound collection signal acquisition unit 130 Sound collection signal extraction unit 140 Frequency spectrum generation unit 150 Fluctuation width determination unit 160 Noise frequency spectrum estimation unit 200 Measurement target 300 Sound collection microphone 400 Measurement target sound frequency spectrum estimation unit 1000 Acoustic evaluation device

Claims (10)

a measurement object sound on/off control unit that performs on/off control to repeatedly turn on/off the output of the measurement object sound, which is sound emitted by the measurement object;
a sound collection signal acquisition unit that acquires a sound collection signal that is a signal obtained by converting a sound including the measurement target sound into an electrical signal;
a sound collection signal extraction unit that extracts, from the sound collection signal, the sound collection signal when the output of the measurement target sound is turned on as a first sound collection signal for that time based on the on/off control, and the sound collection signal when the output of the measurement target sound is turned off as a second sound collection signal for that time based on the on/off control;
a frequency spectrum generating unit that converts the first collected sound signal into a frequency spectrum each time to generate a plurality of first frequency spectra, and converts the second collected sound signal into a frequency spectrum each time to generate a plurality of second frequency spectra;
a fluctuation range determination unit that determines whether a fluctuation range of each frequency component of the plurality of second frequency spectra during a predetermined period is equal to or greater than a predetermined threshold value or is less than the threshold value;
a noise frequency spectrum estimator that estimates, as a noise frequency spectrum, a frequency spectrum of noise included in the plurality of first frequency spectra based on the plurality of first frequency spectra, the plurality of second frequency spectra, and a determination result of the fluctuation range determiner;
A noise evaluation device comprising: The noise frequency spectrum estimator
For frequency components of the second frequency spectrum whose fluctuation range is less than the threshold, an average value of each frequency component of the second frequency spectrum over the predetermined period is set as the frequency component of the noise frequency spectrum;
For frequency components of the second frequency spectrum whose fluctuation range is equal to or greater than the threshold, a minimum value of the frequency components of the second frequency spectrum during the predetermined period is set as the frequency component of the noise frequency spectrum.
2. The noise evaluation device according to claim 1. The noise frequency spectrum estimator
For frequency components of the second frequency spectrum whose fluctuation range is less than the threshold, a median value of each frequency component of the second frequency spectrum during the predetermined period is set as a frequency component of the noise frequency spectrum;
For frequency components of the second frequency spectrum whose fluctuation range is equal to or greater than the threshold, a minimum value of the frequency components of the second frequency spectrum during the predetermined period is set as the frequency component of the noise frequency spectrum.
2. The noise evaluation device according to claim 1. The noise evaluation device according to any one of claims 1 to 3;
a measurement target sound frequency spectrum estimation unit that estimates a measurement target sound frequency spectrum, which is the frequency spectrum of the measurement target sound, based on the first frequency spectrum and the noise frequency spectrum;
An acoustic evaluation device comprising: The measurement target sound frequency spectrum estimation unit
estimating the measurement target sound frequency spectrum by subtracting each frequency component of the noise frequency spectrum from each frequency component of the average value of the frequency components of the first frequency spectrum during the predetermined period;
5. The acoustic evaluation device according to claim 4. The measurement target sound frequency spectrum estimation unit
For frequency components of the second frequency spectrum whose fluctuation range is less than the threshold, the average value of each frequency component of the second frequency spectrum during the predetermined period is subtracted from the average value of each frequency component of the first frequency spectrum, thereby obtaining the frequency components of the measurement target sound frequency spectrum;
For frequency components of the second frequency spectrum whose fluctuation range is equal to or greater than the threshold value, the minimum value of each frequency component of the first frequency spectrum during the predetermined period is set as the frequency component of the measurement target sound frequency spectrum.
5. The acoustic evaluation device according to claim 4. The computer
On/off control is performed by repeatedly turning on and off the output of the measurement target sound, which is sound emitted by the measurement target;
Acquire a collected sound signal, which is a signal obtained by converting a sound including the measurement target sound into an electrical signal,
Based on the on/off control, the sound collection signal when the output of the measurement target sound is turned on is set as a first sound collection signal for that time, and the sound collection signal when the output of the measurement target sound is turned off is set as a second sound collection signal for that time, and these are extracted from the sound collection signal;
Converting the first collected sound signal into a frequency spectrum each time to generate a plurality of first frequency spectra, and converting the second collected sound signal into a frequency spectrum each time to generate a plurality of second frequency spectra,
determining whether a fluctuation range of each frequency component of the plurality of second frequency spectra in a predetermined period is equal to or greater than a predetermined threshold or less than the threshold;
estimating a frequency spectrum of noise contained in the plurality of first frequency spectra as a noise frequency spectrum based on the plurality of first frequency spectra, the plurality of second frequency spectra, and the determination result of the fluctuation range;
A noise evaluation method comprising: The computer
The noise evaluation method according to claim 7, further comprising estimating the noise frequency spectrum,
an acoustic evaluation method comprising: estimating a measurement target sound frequency spectrum, which is the frequency spectrum of the measurement target sound, based on the first frequency spectrum and the noise frequency spectrum. a process of performing on/off control to repeatedly turn on/off the output of the measurement target sound, which is sound emitted by the measurement target;
A process of acquiring a collected sound signal, which is a signal obtained by converting a sound including the measurement target sound into an electrical signal;
a process of extracting, from the sound collection signal, the sound collection signal when the output of the sound to be measured is turned on as a first sound collection signal for that time based on the on/off control, and the sound collection signal when the output of the sound to be measured is turned off as a second sound collection signal for that time;
A process of converting the first collected sound signal into a frequency spectrum each time to generate a plurality of first frequency spectra, and converting the second collected sound signal into a frequency spectrum each time to generate a plurality of second frequency spectra;
determining whether a fluctuation range of each frequency component of the plurality of second frequency spectra in a predetermined period is equal to or greater than a predetermined threshold or less than the threshold;
a process of estimating a frequency spectrum of noise contained in the plurality of first frequency spectra as a noise frequency spectrum based on the plurality of first frequency spectra, the plurality of second frequency spectra, and the determination result of the fluctuation range;
A noise evaluation program that causes a computer to execute the above steps. A process of executing the noise evaluation program according to claim 9;
a process of estimating a measurement target sound frequency spectrum, which is the frequency spectrum of the measurement target sound, based on the first frequency spectrum and the noise frequency spectrum;
An acoustic evaluation program characterized by causing a computer to execute the above.