Masker sound adjustment method and masker sound adjustment device

Abstract

To provide a masker sound control method and a masker sound control device that suppress sound volume of a masker sound while exhibiting mask effects.SOLUTION: In a masker sound control device, a processor 11 comprises a sound volume acquisition unit 101, a sound volume control quantity calculation unit 102, and a sound volume control unit 103. The sound volume acquisition unit 101 acquires sound volume of four frequency bands extracted from a conversation sound picked up by a microphone 15. The sound volume control quantity calculation unit 102 calculates a sound volume control quantity so that the difference in sound volume between the conversation sound and masker sound is equal to or less than a threshold based upon word intelligibility in each frequency band. The sound volume control unit 103 reads the masker sound out of a flash memory 12, and outputs it to a speaker 14 after controlling the sound volume of each frequency band.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] An embodiment of the present invention relates to a masker sound adjustment method and a masker sound adjustment device for adjusting a masker sound for masking a conversation sound. [Background technology]

[0002] Patent Document 1 discloses a masking sound generating device that generates a masking sound for masking conversation sounds.

[0003] Patent Document 2 discloses a masking sound data generating device that adjusts the volume of a masker sound based on different rules for each of two or more frequency bands. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-154138 A [Patent Document 2] JP 2015-187714 A Summary of the Invention [Problem to be solved by the invention]

[0005] It is preferable that the volume of the masking sound is low so as not to cause discomfort or strangeness to the user, but as the volume of the masking sound becomes lower, the masking effect decreases.

[0006] Therefore, an object of one embodiment of the present invention is to provide a masker sound adjustment method and a masker sound adjustment device that suppresses the volume of a masker sound while exerting a masking effect. [Means for solving the problem]

[0007] A masker sound adjustment method according to one embodiment of the present invention determines, in each of a plurality of predetermined frequency bands, an amount of volume adjustment of the masker sound relative to the volume of the conversation sound to be masked, based on a threshold value corresponding to word intelligibility, and adjusts the volume of the masker sound for each of the plurality of frequency bands based on the amount of volume adjustment.

[0008] Alternatively, a masker sound adjustment method according to one embodiment of the present invention acquires a masker sound and an auxiliary content sound for supplementing the masker sound, and outputs the masker sound by restricting a range below a first predetermined frequency and exceeding a second predetermined frequency, and outputs the auxiliary content sound without restricting a range below the first predetermined frequency and exceeding the second predetermined frequency. Effect of the Invention

[0009] According to one embodiment of the present invention, it is possible to suppress the volume of the masking sound while still achieving a masking effect. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a block diagram showing a configuration of a masking sound output device 1. [Diagram 2] 2 is a block diagram showing the functional configuration of the processor 11. FIG. [Diagram 3] 10 is a flowchart showing a masking sound adjustment method. [Figure 4] FIG. 11 is a diagram illustrating SNR thresholds for each frequency band. [Diagram 5] FIG. 13 is a block diagram showing a functional configuration of a processor 11 according to a first modified example. [Figure 6] FIG. 11 is a block diagram showing a functional configuration of a processor 11 according to a second modified example. [Figure 7] 10 is a flowchart showing a masking sound adjustment method according to Modification 2. [Figure 8] FIG. 11 is a block diagram showing a functional configuration of a processor 11 according to a third modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] 1 is a block diagram showing the configuration of a masker sound output device 1. The masker sound output device 1 includes a processor 11, a flash memory 12, a RAM 13, a speaker 14, and a microphone 15.

[0012] The masking sound output device 1 outputs a masking sound for masking conversation sounds from a speaker 14. The masking sound output device 1 adjusts the masking sound so as not to give the user a sense of discomfort or strangeness and so as to exert a masking effect.

[0013] The processor 11 performs various operations by reading out programs from the flash memory 12, which is a storage medium, and temporarily storing the programs in the RAM 13. The programs include a masker sound adjustment program 121. The flash memory 12 also stores other programs for the operation of the processor 11, such as firmware. The flash memory 12 also stores sound data of a masker sound. The masker sound is, for example, a noise sound. The masker sound may be any sound that inhibits the hearing of conversation sounds. For example, the masker sound may be a disturbing sound for disturbing the hearing of conversation sounds. The disturbing sound is, for example, a conversation sound (a sound that has no lexical meaning) that is produced by processing the voice of an arbitrary speaker and whose content cannot be understood.

[0014] It should be noted that the program read by processor 11 does not need to be stored in flash memory 12 within the device itself. For example, the program may be stored in a storage medium of an external device such as a server. In this case, processor 11 may read the program from the server into RAM 13 each time and execute it. Also, the masker sound does not need to be stored in flash memory 12. The masker sound may be downloaded each time from an external device such as a server.

[0015] The microphone 15 picks up conversation sounds. The processor 11 adjusts the volume of the masking sound based on the volume of the conversation sounds picked up by the microphone 15. Note that the sounds picked up by the microphone 15 include not only the voice of the speaker but also various types of background noises and the like.

[0016] Fig. 2 is a block diagram showing the functional configuration of the processor 11. The processor 11 realizes the masker sound adjustment device of the present invention. As shown in Fig. 2, the processor 11 functionally comprises a volume acquisition unit 101, a volume adjustment amount calculation unit 102, and a volume adjustment unit 103. These configurations are realized by a masker sound adjustment program 121.

[0017] The volume acquisition unit 101 acquires conversation sound by the microphone 15. The volume adjustment amount calculation unit 102 calculates the volume of the acquired conversation sound. The volume adjustment unit 103 reads out a masking sound from the flash memory 12 and adjusts the volume of the masking sound.

[0018] FIG. 3 is a flowchart showing a masking sound adjustment method. First, the volume acquisition unit 101 collects conversation sounds with the microphone 15 (S11). Then, the volume acquisition unit 101 extracts a plurality of frequency bands from the collected sounds by using a bandpass filter (S12). In the example of FIG. 2, the volume acquisition unit 101 has four 1 / 1 octave band filters of a 500 Hz band, a 1 kHz band, a 2 kHz band, and a 4 kHz band. Specifically, the four 1 / 1 octave band filters pass frequencies of 355 Hz to 710 Hz in the 500 Hz band, 710 Hz to 1.4 kHz in the 1 kHz band, 1.4 kHz to 2.8 kHz in the 2 kHz band, and 2.8 kHz to 5.6 kHz in the 4 kHz band, respectively. In this way, the volume acquisition unit 101 extracts the four frequency bands from the sound signal.

[0019] Thereafter, the volume acquisition unit 101 acquires the volume of each of the extracted frequency bands (S13). Then, the volume adjustment amount calculation unit 102 calculates the volume adjustment amount of the masker sound in each of the four frequency bands (S14). The volume adjustment amount calculation unit 102 calculates the volume adjustment amount so that the difference between the volume (dB) of the conversation sound and the volume (dB) of the masker sound, that is, the SNR (Signal to Noise Ratio), which is the volume ratio of the conversation sound to the masker sound, is equal to or less than a threshold based on word intelligibility. Note that since background noise is also a type of noise, the SNR is expressed as SNR=Singal (volume of the conversation sound)-Noise (volume of the masker sound+volume of the background noise), where the conversation sound is Signal and the masker sound and background noise are Noise.

[0020] FIG. 4 is a diagram showing the SNR threshold for each frequency band. The horizontal axis of the graph shown in FIG. 4 is frequency (Hz), and the vertical axis is volume (dB). The SNR threshold is obtained based on the word intelligibility. The word intelligibility was obtained by an experiment. In an experiment, the inventor of the present application played word sounds and masker sounds (noise sounds) to multiple listeners. The inventor of the present application played word sounds and masker sounds to multiple listeners under the same SNR condition, and obtained the number of experimental trials in which the content of the word could be understood for each band out of the total number of experimental trials as the word intelligibility. In other words, a word intelligibility of 50% means that the number of experimental trials in which the content of the word could be understood out of the total number of experimental trials is about 50%. A word intelligibility of 20% means that the number of experimental trials in which the content of the word could be understood out of the total number of experimental trials is only about 20%. It is considered that a word intelligibility of 50% makes it difficult for listeners to understand the content of the conversation, and a word intelligibility of 20% makes it impossible for listeners to understand the content of the conversation at all. In other words, if the word intelligibility is 50%, the masker sound has a masking effect. If the word intelligibility is 20%, the masker sound has an extremely strong masking effect.

[0021] The inventors of the present application changed the volume of the masker sound in each of a number of frequency bands to change the SNR, and obtained the word intelligibility for each band. Figure 4 is a graph showing the volume (threshold) of the SNR versus the word intelligibility based on the experimental results.

[0022] From the experimental results shown in Fig. 4, it can be seen that the SNR threshold based on word intelligibility is the lowest value in the octave band with a center frequency of 1 to 4 kHz. In the experimental results shown in Fig. 4, the threshold was the lowest in the 1 / 1 octave band with a center frequency of 2 kHz, and SNR = -15 dB at word intelligibility of 50%. In addition, the SNR threshold based on word intelligibility becomes higher in the higher and lower frequency bands on either side of the octave band with a center frequency of 2 kHz.

[0023] Therefore, the volume adjustment amount calculation unit 102 can exert a masking effect on the masking sound by determining a volume adjustment amount for the masking sound such that the SNR is at most −15 dB in an octave band with a center frequency of 2 kHz.

[0024] In order to most efficiently exert the masking effect, it is preferable that the volume adjustment amount calculation unit 102 determines a volume adjustment amount that makes the SNR below the threshold for word intelligibility of 20% in all of the 500 Hz band, the 1 kHz band, the 2 kHz band, and the 4 kHz band.

[0025] However, the SNR threshold based on word intelligibility is not limited to the value shown in this embodiment.

[0026] 4 are stored in the flash memory 12. The volume adjustment amount calculation unit 102 reads out the threshold value of each frequency band from the flash memory 12. The volume adjustment amount calculation unit 102 calculates the volume adjustment amount of the masker sound by adding the volume of each frequency band acquired by the volume acquisition unit 101 to the threshold value of each frequency band.

[0027] The volume adjustment unit 103 is composed of, for example, an equalizer. The volume of the masking sound in each band is adjusted by the volume adjustment amount calculated by the volume adjustment amount calculation unit 102 (S15). The volume adjustment unit 103 outputs the masking sound after the volume adjustment to the speaker 14 (S16). This allows the masking sound output device 1 to suppress the volume of the masking sound while exerting a masking effect. Note that the volume adjustment unit 103 may be a band pass filter (BPF) and a gain adjuster instead of an equalizer. In this case, the BPF divides the masking sound into the above four frequency bands, and the gain adjuster adjusts the volume of each masking sound.

[0028] As described above, the sound acquired by the microphone 15 also includes background noise. Therefore, the volume adjustment amount calculation unit 102 may obtain the volume adjustment amount of the masking sound by subtracting the volume of the background noise from the threshold value. The volume of the background noise may be a predetermined value, or the volume of the background noise may be obtained from the sound acquired by the microphone 15.

[0029] The processor 11 may also include a sound source separation unit that removes background noise from the sound collected by the microphone 15 to separate the conversation sound. The sound source separation unit separates the conversation sound using, for example, a spectrum subtraction or a Wiener filter that removes background noise with the conversation sound as the target sound. In this case, the volume acquisition unit 101 acquires the volume of the separated conversation sound. This allows the masking sound output device 1 to further suppress the volume of the masking sound while exerting a masking effect. The masking sound adjustment method may separate the conversation sound and the background noise by the arrangement of the microphone 15 and the directivity of the microphone 15. For example, when the position of the speaker is fixed, such as a table for a meeting in an office, the masking sound adjustment method can separate the conversation sound by placing the microphone 15 at the position of the speaker and acquiring only the voice of the speaker at a high volume. When the position of the head of the speaker when sitting in a chair is fixed, the masking sound adjustment method may direct the directivity of the microphone 15 to the position of the speaker's head. In addition, the masking sound adjustment method may involve setting another microphone for acquiring background noise at a location other than the speaker, or directing the microphone in a direction other than the speaker. In this case, the masking sound adjustment method may involve removing the background noise from the sound acquired by the microphone 15 using the background noise acquired by the microphone. Note that in the octave bands with a center frequency of less than 500 Hz and the octave bands with a center frequency of more than 4 kHz, the word intelligibility was not affected regardless of the SNR value. In other words, the volume of the octave bands with a center frequency of less than 500 Hz and more than 4 kHz did not affect the masking effect. This shows that masking sounds are not necessary in the octave bands with a center frequency of less than 500 Hz and more than 4 kHz.

[0030] Fig. 5 is a block diagram showing a functional configuration of the processor 11 according to Modification 1. Configurations common to those in Fig. 2 are given the same reference numerals and description thereof will be omitted.

[0031] The processor 11 further includes a bandpass filter (BPF) 104. The BPF 104 corresponds to a band limiting section. The lower limit frequency of the BPF 104 is equal to the lower limit frequency 355 Hz of an octave band filter having a center frequency of 500 Hz. The upper limit frequency of the BPF 104 is equal to the upper limit frequency 5.6 kHz of an octave band filter having a center frequency of 4 kHz. This allows the BPF 104 to limit the masker sound in the octave band having a center frequency less than 500 Hz and more than 4 kHz. Therefore, the processor 11 of the first modification can further reduce the discomfort and strangeness caused by the masker sound while exerting a masking effect.

[0032] 6 is a block diagram showing a functional configuration of the processor 11 according to the modified example 2. The processor 11 according to the modified example 2 functionally includes an acquisition unit 201, a BPF 202, and an output unit 203. These configurations are realized by the masker sound adjustment program 121.

[0033] 7 is a flowchart showing a masker sound adjustment method according to Modification 2. The acquisition unit 201 acquires a masker sound and an auxiliary content sound for supplementing the masker sound from the flash memory 12 (S21).

[0034] The auxiliary content sound includes, for example, background sound that is output steadily and dramatic sound that is output non-steadily. The background sound is, for example, a natural sound such as a babbling river or the rustling of trees. The background sound may also be a musical sound. The dramatic sound is, for example, a bird's song or an intermittent melody sound, and is a sound that is repeated randomly.

[0035] The background sound makes the masking sound less noticeable, reducing the discomfort and strangeness caused by the masking sound, while the dramatic sound attracts the listener's attention, preventing the masking effect from decreasing due to habituation to the masking sound.

[0036] The acquisition unit 201 outputs the masker sound to the BPF 202 to limit the range of the masker sound below a first predetermined frequency and above a second predetermined frequency (S22). The first predetermined frequency is, for example, the lower limit frequency (355 Hz) of an octave band with a center frequency of 500 Hz as described above. The second predetermined frequency is, for example, the upper limit frequency (5.6 kHz) of an octave band with a center frequency of 4 kHz.

[0037] The masker sound is band-limited by BPF 202 and input to output unit 203. On the other hand, the auxiliary content sound is input to output unit 203 without being band-limited by BPF 202. That is, output unit 203 outputs the masker sound by restricting the range below a first predetermined frequency and exceeding a second predetermined frequency, and outputs the auxiliary content sound including the range below the first predetermined frequency and exceeding the second predetermined frequency band (S23).

[0038] As described above, the masking sound does not have a masking effect in octave bands with center frequencies below 500 Hz and above 4 kHz. On the other hand, the auxiliary content sound improves the masking effect of the masking sound by reducing the discomfort and strangeness of the masking sound. The auxiliary content sound improves the masking effect of the masking sound by reducing the discomfort and strangeness of the masking sound even in bands below 500 Hz and above 4 kHz.

[0039] The masking sound adjustment method according to Modification 2 outputs only the auxiliary content sound without including the masking sound in the bands below 500 Hz and above 4 kHz. Therefore, the masking sound adjustment method according to Modification 2 can make the auxiliary content sound more prominent and further reduce the discomfort and strangeness caused by the masking sound.

[0040] The configurations of Modification 1 and Modification 2 may be combined. Fig. 8 is a block diagram showing a functional configuration of the processor 11 according to Modification 3. The same components as those shown in Fig. 5 and Fig. 6 are denoted by the same reference numerals, and the description thereof will be omitted.

[0041] 8, the volume adjustment unit 103 adjusts the volume of the masking sound that has been band-limited by the BPF 202. The volume adjustment unit 103 outputs the masking sound whose volume has been adjusted to the output unit 203.

[0042] The masking sound adjustment method according to Modification 3 also outputs only the auxiliary content sound without including the masking sound in bands below 500 Hz and above 4 kHz. Therefore, the masking sound adjustment method according to Modification 3 also makes the auxiliary content sound more prominent, and further reduces the discomfort and strangeness of the masking sound, improving the masking effect of the masking sound.

[0043] Volume adjustment unit 103 reduces the volume of the masking sound more than in Variation 1 shown in Fig. 5. The auxiliary content sound in Variation 3 has an improved masking effect for the masking sound, so that the masking effect of the masking sound can be maintained by the auxiliary content sound even if volume adjustment unit 103 reduces the volume of the masking sound. Thus, the masking sound adjustment method of Variation 3 can further reduce the discomfort and strangeness caused by the masking sound while still exerting a masking effect.

[0044] The description of the present embodiment should be considered as illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims, not by the above-described embodiments. Furthermore, the scope of the present invention includes the scope equivalent to the claims.

[0045] For example, the masking sound adjustment method of the above embodiment adjusts the volume of the masking sound based on the volume of the conversation sound acquired by the microphone 15. However, the masking sound adjustment method may adjust the volume of the masking sound based on a predetermined average volume of the conversation sound.

[0046] Furthermore, the masking sound adjustment method of the above embodiment adjusts the volume of the sound signal of the masking sound output to the speaker 14. However, the masking sound adjustment method may adjust the volume (frequency characteristics) of the masking sound emitted from the speaker 14 and reaching the listener by adjusting the frequency characteristics of the speaker 14. Alternatively, the masking sound adjustment method may adjust both the sound signal and the frequency characteristics of the speaker 14 to adjust the volume (frequency characteristics) of the sound reaching the listener. [Explanation of symbols]

[0047] 1...Masker sound output device 11…Processor 12. Flash memory 13…RAM 14…Speaker 15…Mike 101...Volume acquisition unit 102...Volume adjustment amount calculation unit 103...Volume control 104…BPF 121...Masker sound adjustment program 201…Acquisition Department 202…BPF 203...Output section

Claims

1. determining an amount of volume adjustment of the masker sound relative to the volume of the conversation sound to be masked in each of a plurality of predetermined frequency bands based on a threshold value corresponding to word intelligibility; A masker sound adjustment method for adjusting a volume of the masker sound for each of the plurality of frequency bands based on the volume adjustment amount, The threshold value is a value indicating the volume of the conversation sound relative to the volume of the noise sound including the masker sound, and is the lowest value in a frequency band of 1 to 4 kHz. How to adjust the masking sound.

2. collecting the conversation sound to be masked and acquiring the volume of the conversation sound for each of the plurality of frequency bands; The method for adjusting a masker sound according to claim 1 .

3. Separating the conversation sound from the sound picked up by the microphone; obtaining a volume of the separated conversation sound; The method for adjusting a masker sound according to claim 2.

4. The threshold value is higher in a higher frequency band and a lower frequency band on either side of the frequency band in which the threshold value is the lowest. The method for adjusting a masker sound according to claim 1 .

5. restricting a frequency band of the masker sound lower than an octave band having a center frequency of 500 Hz and a frequency band higher than an octave band having a center frequency of 4 kHz; The method for adjusting a masker sound according to any one of claims 1 to 4.

6. The volume adjustment amount is determined so that a value indicating the volume of the conversation sound relative to the volume of the noise sound including the masker sound is −15 dB or less in an octave band having a center frequency of 2 kHz. The method for adjusting a masker sound according to any one of claims 1 to 5.

7. a volume adjustment amount calculation unit that calculates a volume adjustment amount of a masker sound relative to a volume of a conversation sound to be masked in each of a plurality of predetermined frequency bands based on a threshold value corresponding to word intelligibility; a volume adjustment unit that adjusts the volume of the masking sound for each of the plurality of frequency bands based on the volume adjustment amount; A masker sound adjustment device comprising: The threshold value is a value indicating the volume of the conversation sound relative to the volume of the noise sound including the masker sound, and is the lowest value in a frequency band of 1 to 4 kHz. A masker sound adjustment device characterized by:

8. a volume acquisition unit that collects the conversation sound to be masked and acquires the volume of the conversation sound for each of the plurality of frequency bands; The masker sound adjustment device according to claim 7, further comprising:

9. A sound source separation unit is provided to separate the conversation sound from a sound picked up by a microphone, The volume acquisition unit acquires the volume of the separated conversation sound.

9. The masker sound adjustment device according to claim 8.

10. The threshold value is higher in a higher frequency band and a lower frequency band on either side of the frequency band in which the threshold value is the lowest.

8. The masker sound adjustment device according to claim 7.

11. a band limiting unit for limiting a band of the masker sound lower than an octave band having a center frequency of 500 Hz and a band of the masker sound higher than an octave band having a center frequency of 4 kHz; 11. The masker sound adjustment device according to claim 7,

12. the volume adjustment amount calculation unit calculates the volume adjustment amount so that a value indicating the volume of the conversation sound relative to the volume of the noise sound including the masker sound is −15 dB or less in an octave band having a center frequency of 2 kHz.

12. The masker sound adjustment device according to claim 7, wherein the masker sound adjustment device is a sound masking device.

13. A computer comprising: determining an amount of volume adjustment of the masker sound relative to the volume of the conversation sound to be masked, in each of a plurality of predetermined frequency bands, based on a threshold value corresponding to word intelligibility; adjusting the volume of the masker sound for each of the plurality of frequency bands based on the volume adjustment amount; A program for executing a process, The threshold value is a value indicating the volume of the conversation sound relative to the volume of the noise sound including the masker sound, and is the lowest value in a frequency band of 1 to 4 kHz. program.

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