Masking sound generation system

Abstract

We provide technology that can generate optimal masking sounds. [Solution] The masking sound generation system 100 includes a microphone 10 (input unit) into which a sound to be masked (external noise, internal noise, etc.) is input, a speaker 20 (output unit) that outputs a masking sound for the sound to be masked, and a control unit 30 connected to the microphone 10 and speaker 20 that generates the masking sound. The control unit 30 sets the masking sound to a base sound (base masking sound) of broadband natural environmental sound including sounds such as the babbling of a river, and if the level of the sound to be masked input to the microphone 10 exceeds the level of the base sound, the control unit 30 sets the masking sound to a sound with an additional sound (additional masking sound) added to the base sound.

Description

[Technical Field]

[0001] The present invention relates to a masking sound generating system that generates a masking sound. [Background Art]

[0002] Patent Document 1 discloses a technique of controlling the volume of a masking sound by following temporal fluctuations of collected sound. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2012-053335 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] Although techniques such as that disclosed in Patent Document 1 are known as conventional techniques, a technique capable of generating an optimal masking sound is desired.

[0005] Accordingly, an object of the present invention is to provide a technique that can generate an optimal masking sound. [Means for Solving the Problem]

[0006] The present invention adopts the following solution to solve the above problem. Note that the following solution and the wording in parentheses are merely examples, and the present invention is not limited thereto. Further, the present invention can be an invention that includes at least one of the invention-specifying matters set forth in the following solution. Furthermore, a subordinate concept can be formed by adding elements that limit the invention-specifying matters to each invention-specifying matter set forth in the following solution, and a superordinate concept can also be formed by deleting elements that limit the invention-specifying matters.

[0007] Solution 1: The masking sound generation system of this solution comprises an input unit into which a sound to be masked is input, an output unit that outputs a masking sound for the sound to be masked, and a control unit connected to the input unit and the output unit that generates the masking sound, wherein the control unit uses the masking sound as a base masking sound, and if the level of the sound to be masked input to the input unit exceeds the level of the base masking sound, the masking sound is made by adding an additional masking sound to the base masking sound.

[0008] According to this solution, depending on the level of the sound to be masked, it is possible to output only the bass masking sound, or the bass masking sound and additional masking sounds, thereby generating the optimal masking sound according to the situation. Furthermore, according to this solution, additional masking sounds are added to the bass masking sound only when the level of the sound to be masked exceeds the level of the bass masking sound. Therefore, in situations where the sound to be masked does not occur, or when the level of the sound to be masked is low, the bass masking sound can be used as normal background music (BGM, sound played in the background, sound played to create atmosphere).

[0009] Solution 2: The masking sound generation system of this solution is a masking sound generation system characterized in that, in any of the solutions described above, the base masking sound is a natural environmental sound.

[0010] According to this solution, since the base masking sound is a natural environmental sound, the masking sound is less likely to become jarring to the ear even if the volume is increased to a certain extent.

[0011] Solution 3: The masking sound generation system of this solution is a masking sound generation system characterized in that, in any of the solutions described above, the control unit generates a natural ambient sound as the additional masking sound, which follows the level fluctuations of the sound to be masked and whose playback level is varied.

[0012] This solution makes it possible to make fluctuating masking sounds less audible while preventing additional masking sounds from becoming excessively loud.

[0013] Solution 4: The masking sound generation system of this solution is a masking sound generation system characterized in that, in any of the solutions described above, the control unit generates a natural ambient sound corresponding to the level or frequency characteristics of the sound to be masked as the additional masking sound.

[0014] According to this solution, the volume of the base masking sound is not changed, and sounds that occur suddenly can be instantly masked without causing any unnaturalness, making the fluctuating sound to be masked less audible.

[0015] Solution 5: The masking sound generation system of this solution is a masking sound generation system characterized in that, in any of the solutions described above, the control unit generates a natural environmental sound as the additional masking sound, which follows the fluctuations in the frequency characteristics of the sound to be masked and has fluctuated frequency characteristics.

[0016] According to this solution, by varying only specific frequencies among natural ambient sounds with broadband frequency characteristics, it is possible to instantly mask suddenly occurring sounds without causing discomfort, and to make the fluctuating masked sounds less audible.

[0017] Solution 6: The masking sound generation system of this solution is a masking sound generation system characterized in that, in any of the solutions described above, the control unit generates the natural environmental sound within a predetermined range of levels.

[0018] According to the present solution, since natural environmental sound is generated within a predetermined level range, it is possible to prevent the natural environmental sound serving as additional masking sound from becoming excessively loud.

[0019] Solution 7: A masking sound generation system according to the present solution is characterized in that, in any one of the above solutions, the control section generates, as the additional masking sound, a sound obtained by adding an ultra-high frequency sound to the natural environmental sound.

[0020] According to the present solution, since a sound obtained by adding an ultra-high frequency sound to a natural environmental sound is generated as the additional masking sound, discomfort can be further reduced. Effects of the Invention

[0021] According to the present invention, an optimal masking sound can be generated. Brief Description of the Drawings

[0022] [Figure 1] It is a diagram showing a masking sound generation system 100 according to an embodiment. [Figure 2] It is a diagram showing control contents and a configuration of the masking sound generation system 100. [Figure 3] It is a diagram showing details of control contents of Configuration 1 and Configuration 2. [Figure 4] It is a diagram showing details of control contents of Configuration 3. [Figure 5] It is a diagram showing the flow of a psychological and physiological experiment performed by the masking sound generation system 100. [Figure 6] It is a diagram showing level fluctuations of a presented sound used in the experiment of Fig. 5. [Figure 7] It is a diagram showing experimental results of Fig. 5. Mode for Carrying Out the Invention

[0023] Embodiments of the present invention will be described below with reference to the drawings. Note that the following embodiments are preferred examples of a masking sound generation system, and the present invention is not limited to these examples.

[0024] Figure 1 shows a masking sound generation system 100 according to an embodiment. The masking sound generation system 100 is a system that generates a masking sound for a sound to be masked. The masking sound generation system 100 employs a method for generating auditory masking background music (BGM) using natural environmental sounds with a wide frequency range as the base sound. The masking sound generation system 100 consists of a computer on which the programs and software necessary for system processing are implemented, and various devices connected to it.

[0025] The masking sound generation system 100 comprises a microphone 10 (input unit), a speaker 20 (output unit), and a control unit 30. Microphone 10 is a device that receives the sound to be masked. The sound to be masked can be external noise or internal noise. External noise includes, for example, construction noise, road noise, railway noise, and equipment noise. Internal noise includes, for example, conversation sounds, air conditioning noise, and medical sounds. Internal noise (room noise) can be any noise occurring within the same room.

[0026] Microphone 10 is preferably a sound-collecting microphone. A sound-collecting microphone is a device that collects the sound to be masked. Examples of sound-collecting microphones include directional microphones, omnidirectional microphones, and all-weather microphones. By monitoring the sound to be masked with microphone 10, the volume and frequency characteristics required for the additional masking sound can be determined.

[0027] Speaker 20 is a device that outputs a masking sound for the sound to be masked. Speaker 20 can be equipped with an amplifier. The speaker can be a directional speaker, an omnidirectional speaker, etc.

[0028] The control unit 30 is connected to the microphone 10 and speaker 20 and generates a masking sound. By outputting a masking sound from speaker 20, user discomfort caused by external or internal noise can be reduced. Details of the masking sound will be described later.

[0029] The data and settings handled by the control unit 30, as well as the data for the base sound and additional sounds, are stored in a memory unit (not shown) as needed. The computer constituting the masking sound generation system 100 is a computer (for example, a PC, cloud server, smartphone, tablet terminal, etc.) equipped with a CPU, RAM, HDD, various I / Fs, etc., and the CPU of the computer functions as the control unit 30 when a program is implemented on the computer. The memory unit stores a program that causes the control unit 30 (computer) to execute the control procedure of the masking sound generation system 100. Alternatively, instead of this configuration, a computer dedicated to the masking sound generation system 100 may be designed and equipped with a configuration corresponding to the control unit 30.

[0030] Furthermore, at least one of the microphone 10, speaker 20, and control unit 30 may be connected to a computer via a network or cable, and at least one of these functions may be connected to a second computer separate from the first computer on which the program and the like are implemented, and the first computer and the second computer may be connected via a network or the like.

[0031] Figure 2 shows the control details and configuration of the masking sound generation system 100. Microphone 10 monitors the sound to be masked (e.g., noise). Speaker 20 outputs the masking sound generated by control unit 30. Control unit 30 determines what kind of masking sound to generate.

[0032] The general control flow performed by the control unit 30 is as follows: (1) Level determination of the sound to be masked, (2) Generation of the masking sound, and (3) Output of the masking sound. The following will explain this flow in order.

[0033] [(1) Determining the level of the sound to be masked] The control unit 30 determines the level of the sound to be masked. Specifically, the control unit 30 performs a process to determine whether the sound to be masked input to the microphone 10 is louder or quieter than the bass sound (the bass masking sound). If they are at the same level, they may be included in either the louder or quieter group. The bass sound can be set to, for example, around 30 to 50 dB.

[0034] If the sound to be masked input to microphone 10 is quieter than the base tone, the control unit 30 sets the masking sound to the base tone (a broadband natural ambient sound). In other words, if the sound to be masked input to microphone 10 is quieter than the base tone, the control unit 30 does not generate an additional sound. The base tone is always output, regardless of the level determination result.

[0035] Broadband ambient sounds are a mixture of various sounds found in the natural environment (such as the sound of water, wind, and animals). Broadband ambient sounds can include sounds such as the babbling of a stream. Because broadband ambient sounds have a broad frequency response, they can make the sound to be masked less audible, regardless of the frequency response of the sound to be masked.

[0036] On the other hand, if the sound to be masked input to microphone 10 is louder than the bass sound (if the level of the sound to be masked input to the input unit exceeds the level of the bass sound), the control unit 30 will set the masking sound to be the bass sound plus an additional sound (an additional masking sound). In other words, if the sound to be masked input to microphone 10 is louder than the bass sound, the control unit 30 will generate an additional sound (if the sound to be masked exceeds the level of the bass sound, it will play an additional masking sound).

[0037] [(2) Generation of masking sounds] As a method for generating additional sounds to be added to the bass sound, one of the following three configurations can be adopted. Configurations 1 to 3 may be implemented in the masking sound generation system 100 by implementing only one of them, or multiple configurations may be implemented in the masking sound generation system 100.

[0038] When multiple configurations are implemented in the masking sound generation system 100, the configuration may be changed by user operation, or it may be configured to automatically switch configurations based on predetermined conditions (such as temporal conditions like configuration 1 in the first time period, configuration 2 in the second time period, and configuration 3 in the third time period, or conditions related to the noise level of the sound to be masked, such as configuration 1 if the noise level of the sound to be masked is within the first range, configuration 2 if it is within the second range, and configuration 3 if it is within the third range). The following explains the three components in order.

[0039] [Structure 1] In configuration 1, the control unit 30 tracks the level fluctuations of the sound to be masked and causes the level of the natural ambient sound (additional sound) to fluctuate.

[0040] [Structure 2] In configuration 2, the control unit 30 plays a natural ambient sound (additional sound) that corresponds to the level or frequency characteristics of the sound to be masked.

[0041] [Structure 3] In configuration 3, the control unit 30 tracks the fluctuations in the frequency characteristics of the sound to be masked and changes the frequency characteristics of the natural environmental sound (additional sound).

[0042] In configurations 1 to 3, the control unit 30 may generate an additional sound by adding an ultra-high frequency sound to a natural environmental sound (a sound generated as an additional sound in configurations 1 to 3).

[0043] [(3) Output of masking sound] If the control unit 30 does not generate additional sounds, it outputs only the bass tone from the speaker 20 as a masking tone. On the other hand, if the control unit 30 generates additional sounds according to configurations 1 to 3, it outputs both the bass tone and the additional sounds from the speaker 20 as masking sounds.

[0044] Figure 3 shows the details of the control systems for Configuration 1 and Configuration 2. In each graph in the figure, the vertical axis represents noise level (dB), and the horizontal axis represents time (s). Thin lines in the graphs represent indoor noise, dashed lines represent bass tones, and thick lines represent additional tones.

[0045] [Structure 1] With Configuration 1 in place, if intermittent noise (e.g., railway noise) as shown in Figure (1) occurs, the control unit 30 generates a natural ambient sound as an additional sound, which follows the level fluctuations of the sound to be masked and varies the playback level.

[0046] In the example shown in Figure (1), five trains pass by, and the level of indoor noise increases each time a train passes. The bass tone is constantly output at a constant level, but when the level of indoor noise exceeds the level of the bass tone, an additional tone (a broadband natural ambient sound) is output along with the bass tone (a broadband natural ambient sound). The additional tone is output in accordance with the waveform of the indoor noise in the portion that exceeds the bass tone.

[0047] With Configuration 1 in place, if fluctuating noise (e.g., construction noise) as shown in (2) of the figure occurs, the control unit 30 generates a natural ambient sound as an additional sound, which follows the level fluctuations of the sound to be masked and has a fluctuating playback level. In the example shown in Figure (2), multiple sudden construction noises occur, and each time a construction noise occurs, the indoor noise level increases. The bass tone is constantly output at a constant level, but when the indoor noise level exceeds the bass tone level, an additional tone (broadband natural ambient sound) is output along with the bass tone (broadband natural ambient sound). The additional tone is output in accordance with the waveform of the indoor noise in the portion that exceeds the bass tone level.

[0048] The bass sound in Configuration 1 is a broadband natural environmental sound, and the additional sound in Configuration 1 is also a broadband natural environmental sound similar to the bass sound in Configuration 1. As shown in Configuration 1, by outputting additional sounds in accordance with the waveform of the indoor noise, the bass sound and additional sounds can be made to closely follow changes in the indoor noise.

[0049] In configuration 1, it is preferable that the control unit 30 generates natural ambient sounds with varying playback levels within a predetermined range. When the level range of the additional sound is set in this way, the additional sound will not exceed the upper limit of the level range (it will cap out). The level range of the additional sound can be set to approximately +5 to +25 dB relative to the bass sound.

[0050] [Structure 2] When configuration 2 is in place and intermittent noise (e.g., railway noise) occurs, the control unit 30 generates additional sounds, such as natural ambient sounds (e.g., waves, wind, water, birdsong, insect sounds, etc.) that correspond to the level or frequency characteristics of the sound to be masked.

[0051] Regarding the level, this can be addressed by matching the noise levels of the sound to be masked and the added sound. Regarding the frequency response, this can be addressed by outputting an added sound corresponding to the pitch of the sound to be masked.

[0052] In the example shown in Figure (1), five trains pass by, and the level of indoor noise increases each time a train passes. The bass tone is constantly output at a constant level, but when the level of indoor noise exceeds the level of the bass tone, an additional sound (a different natural environmental sound from the bass tone, such as the sound of waves) is output along with the bass tone (a broadband natural environmental sound). The additional sound is output at the peak of the indoor noise waveform in the portion that exceeds the bass tone. The additional sound output at the peak can be output for a certain period of time (about a few seconds) (the same applies below).

[0053] When configuration 2 is in place, if fluctuating noise (e.g., construction noise) occurs, the control unit 30 generates additional sounds, such as natural ambient sounds (e.g., waves, wind, water, birdsong, insect sounds, etc.) that correspond to the level or frequency characteristics of the sound to be masked.

[0054] In the example shown in Figure (2), multiple sudden construction noises occur, and the indoor noise level increases each time a construction noise occurs. The bass tone is constantly output at a constant level, but when the indoor noise level exceeds the bass tone level, additional sounds (natural environmental sounds different from the bass tone, such as the sound of crickets, birdsong, waves, wind, etc.) are output along with the bass tone (broadband natural environmental sounds). The additional sounds are output at the peaks of the indoor noise waveform in the portion that exceeds the bass tone level.

[0055] The bass tone of Configuration 2 is a broadband natural ambient sound, while the additional sound of Configuration 2 is a different natural ambient sound (a natural ambient sound with a narrower bandwidth than the bass tone of Configuration 2). As shown in Configuration 2, by outputting an additional sound in accordance with the peak of the indoor noise, it is possible to output an additional sound in accordance with situations where the indoor noise increases. Regarding the peak of the indoor noise, the noise level of the sound to be masked is monitored, and the point where the noise level changes from rising to falling can be determined as the peak.

[0056] In configuration 2, similar to configuration 1, the control unit 30 may generate natural ambient sounds with varying playback levels within a predetermined range (the same applies to configuration 3). When setting the level range for additional sounds in configuration 2, the noise level of the additional sounds will be lower than shown in the figure because it will fall within the level range of the additional sounds.

[0057] Natural ambient sounds, used as additional sounds, can be generated, for example, by following the procedure below. The control unit 30 converts the sound to be masked, collected by the microphone 10, into a spectrum, and then converts the spectrum into MIDI (Musical Instrument Digital Interface) format MIDI data (digital data) that shows the characteristics of each component. The reason for converting to MIDI data is that the signal waveform corresponding to the sound to be masked makes it difficult to understand the structure of the sound to be masked in its original state.

[0058] The control unit 30 converts MIDI data into additional sounds and converts the sound data corresponding to the converted sounds into an audio signal. The audio signal is then transmitted to the speaker 20. The speaker 20 outputs a sound corresponding to the audio signal converted by the control unit 30. This conversion method can be applied not only to configuration 2, but also to configurations 1 and 3.

[0059] In configuration 2, when converting to masking sounds, the MIDI data is divided into high-pitched (sounds around C5), mid-pitched (sounds around C4), and low-pitched (sounds around C3). High-pitched sounds can be used as the sound of crickets, mid-pitched sounds as the sound of birds, and low-pitched sounds as the sound of waves or wind, etc.

[0060] Figure 4 shows the details of the control system for Configuration 3. In each graph in the figure, the vertical axis represents the sound pressure level (dB), and the horizontal axis represents the octave band center frequency (Hz). The light gray vertical bars in the graphs represent the sound to be masked, the white vertical bars represent the bass sound, and the dark gray vertical bars represent the additional sound.

[0061] [Structure 3] In configuration 3, the control unit 30 generates an additional sound, which is a natural ambient sound whose frequency characteristics are altered in response to fluctuations in the frequency characteristics of the sound to be masked. For example, as shown in Figure 4(A), if the frequency characteristics (e.g., sound pressure level) of the sound to be masked exceed those of the bass tone, a natural ambient sound is generated with its frequency characteristics adjusted to match those of the sound to be masked, as shown in Figure 4(B).

[0062] For example, as shown in Figure 4(A), at 500Hz and 2kHz, the sound pressure level of the sound to be masked exceeds the sound pressure level of the bass tone. In this case, as shown in Figure 4(B), an additional sound is generated that matches the sound pressure level of the sound to be masked. As a result, the additional sound will have a sound pressure level that exceeds the bass tone only at 500Hz and 2kHz, and will not exceed the bass tone (will have a sound pressure level equivalent to the bass tone) in other frequency bands.

[0063] In Figure 4(B), three sounds (masking sound, bass sound, and additional sound) are generated simultaneously in each frequency band. However, since the sound pressure levels of the three sounds are added together, no loud sound is generated. For example, in the 63Hz frequency band, the calculation would be approximately 50dB + approximately 30dB + approximately 30dB, but because it is a sum of sound pressure levels, the total of the three sounds is approximately 50.1dB.

[0064] Figure 5 shows the flow of a psychological and physiological experiment using the masking sound generation system 100. The psychological and physiological experiments were conducted in the following manner. (1) The subjects were instructed to imagine a situation where they could hear the sounds of roads and trains coming from a window. (2) The presented sound was presented for 5 minutes after a 2-minute period of silence as a baseline. (3) During the baseline 2 minutes and while the sound presentation was being performed, the participants were instructed to relax and read the designated poetry collection. (4) After the sound presentation, the subjects evaluated their level of pleasure / displeasure, excitement (calmness), and overall impression on a 7-point scale.

[0065] The following three types of sounds are used for presentation: (Sound 1) Indoor noise (railway noise + road traffic noise) (Presentation sound 2) Indoor noise + natural sounds (constant volume) (Presentation sound 3) Indoor noise + natural sounds (fluctuating sounds)

[0066] Figure 6 shows the level fluctuations of the presented sound used in the experiment in Figure 5. In the graph, the vertical axis represents noise level (dBA), and the horizontal axis represents time (m). The black line in the graph represents indoor noise (railway noise + road traffic noise), the light gray line represents natural ambient sound (constant volume), and the dark gray line represents natural ambient sound (fluctuating sound).

[0067] The indoor noise was created by combining recorded railway noise near the tracks and royalty-free road traffic noise, and passing it through a 5mm thick plate glass filter with a 1 / 3 octave band transmission loss. The sound level was 46.5 dBA (L). Aeq,5min ) The natural ambient sounds (constant volume) were created by combining royalty-free natural sounds such as flowing water and birdsong. The sound level is 40.3 dBA (L). Aeq,5min ) The natural ambient sound (fluctuating sound) was created to track fluctuations in indoor noise levels exceeding 40 dBA, and to maintain an indoor noise level of approximately -7 to -10 dB. The sound level was 42.1 dBA (L). Aeq,5min ). Note that the -7 to 10 dB value can be changed as appropriate depending on the level range of the additional sound.

[0068] Figure 7 shows the experimental results from Figure 5. The vertical axis in Figure 7(A) shows the score on a 7-point scale, and the horizontal axis in Figure 7(A) shows the type of sound presented. The gray vertical bars in Figure 7(A) represent the level of discomfort, and the white vertical bars in Figure 7(A) represent the level of calmness. A higher value for discomfort indicates greater discomfort, while a higher value for calmness indicates a calmer state.

[0069] Furthermore, the vertical axis of Figure 7(B) shows the items for impression evaluation, and the horizontal axis of Figure 7(B) shows the scores on a 7-point scale from negative to positive. In addition, the solid line in Figure 7(B) shows the evaluation results for presented sound 1, the dashed line shows the evaluation results for presented sound 2, and the dotted line in Figure 7(B) shows the evaluation results for presented sound 3.

[0070] These experiments revealed the following: (1) The most effective is presented sound 3. Presented sound 3 is the sound corresponding to composition 1 (bass sound + additional sound). (2) While presentation sound 2, which simply adds natural ambient sound (at a constant volume) to indoor noise, is also effective, presentation sound 3 (configuration 1) is more effective. (3) As shown in sound 1, indoor noise alone is unpleasant, unsettling, and negative. (4) Although experimental results are not shown, configurations 2 and 3 are just as effective as configuration 1. Furthermore, configurations 1-3 with added ultra-high frequency sound are just as effective as configuration 1.

[0071] As described above, this embodiment has the following advantages. (1) According to this embodiment, depending on the level of the sound to be masked, it is possible to output only the bass sound or the bass sound and additional sounds, so that the optimal masking sound can be generated according to the situation. Furthermore, according to this embodiment, additional sounds are added to the bass sound only when the level of the sound to be masked exceeds the level of the bass sound, so in situations where the sound to be masked does not occur (quiet situations) or in situations where the level of the sound to be masked is low (situations with low noise levels), the bass sound can be used as normal background music. Moreover, according to this embodiment, only the additional sounds need to be adjusted and the bass sound does not need to be adjusted, so the control processing related to the bass sound can be simplified compared to methods that adjust the bass sound.

[0072] (2) According to this embodiment, since the bass sound is a natural ambient sound, even if the volume is increased to a certain extent, the masking sound is less likely to be jarring to the ear. In addition, in situations where the sound to be masked does not occur, or when the level of the sound to be masked is low, the bass sound can be used as normal ambient background music.

[0073] (3) According to configuration 1 of this embodiment, it is possible to make the fluctuating sound to be masked less audible while preventing the additional sound from becoming excessive.

[0074] (4) According to configuration 2 of this embodiment, the volume of the bass sound can be not changed, and sounds that occur suddenly can be instantly masked without causing any sense of incongruity, making the fluctuating sound to be masked less audible.

[0075] (5) According to configuration 3 of this embodiment, by changing only specific frequencies among natural ambient sounds with broadband frequency characteristics, it is possible to instantly mask suddenly occurring sounds without causing discomfort, and to make the fluctuating sound to be masked less audible.

[0076] (6) According to this embodiment, since natural ambient sounds are generated within a predetermined range of levels, it is possible to avoid the natural ambient sounds, which are added sounds, becoming too loud.

[0077] (7) According to this embodiment, since an additional sound is generated by adding ultra-high frequency sound to natural environmental sounds, the feeling of discomfort can be further reduced.

[0078] (8) According to this embodiment, it is possible to provide a sound environment that reduces stress and improves the wellness of occupants in a noisy environment. Furthermore, the masking sound generation system 100 of this embodiment can be placed in various locations such as offices, residences, commercial facilities, schools, hospitals, hotels, public facilities, music halls, and construction / demolition sites to address noise in the vicinity.

[0079] (9) The technology described in Patent Document 1 has the following problems: (A) If the sound to be masked is loud, the masking sound itself becomes unpleasant to the ear; (B) It cannot be expected to be effective against sounds other than speech, such as construction noise or railway noise. On the other hand, the technology of this embodiment has the following advantages: (a) Since natural ambient sounds can be used as the base sound, the masking sound is less likely to be jarring even if the volume is increased to a certain extent; and (b) It can handle sounds other than speech that are to be masked.

[0080] [Transformed form] The present invention can be implemented in various ways without being limited to the embodiments described above. (1) The masking sound (bass tone) of the bass was explained using examples of natural environmental sounds such as the sound of a babbling brook, but it may also be broadband noise (white noise, pink noise), the sound of a waterfall, the sound of wind, background noise, the sound of percussion instruments, the sound of stringed instruments, or a combination of these. (2) The additional masking sound (additional sound) was explained using the example of a natural environmental sound, but like the base sound in (1) above, it may be any other sound. (3) The content regarding the predetermined range of levels (additional sound level range) does not need to be set. The additional sound level range may be set only for configuration 1, only for configuration 2, only for configuration 3, or for at least two of configurations 1 to 3.

[0081] (4) Ultra-high frequency sounds do not have to be added to the additional sounds. Ultra-high frequency sounds may be added only to configuration 1, only to configuration 2, only to configuration 3, or to at least two of configurations 1 to 3. (5) Configurations 1 to 3 can be used individually or in combination. (6) If the level of the sound to be masked input to microphone 10 exceeds the level of the bass sound, a configuration other than configurations 1 to 3 may be adopted, as long as the masking sound is a sound that is the bass sound with an added sound added. For example, the bass sound and the added sound do not both have to be natural ambient sounds, both may be natural ambient sounds, or only one of them may be a natural ambient sound.

[0082] Furthermore, all other examples shown with illustrations in the embodiments are merely preferred examples and can be modified as appropriate when implementing the present invention. [Explanation of Symbols]

[0083] 10 Microphones 20 speakers 30 Control Unit 100 Masking Sound Generation Systems

Claims

1. The input section receives the sound to be masked, An output unit that outputs a masking sound for the sound to be masked, The system includes a control unit connected to the input and output units for generating the masking sound, The control unit, The aforementioned masking sound will be used as the base masking sound. A masking sound generation system characterized in that, when the level of the sound to be masked input to the input unit exceeds the level of the base masking sound, the masking sound is made by adding an additional masking sound to the base masking sound.

2. In the masking sound generation system according to claim 1, The masking sound generation system is characterized in that the base masking sound is a natural environmental sound.

3. In the masking sound generation system according to claim 1, The control unit generates a natural ambient sound as an additional masking sound, which follows the level fluctuations of the sound to be masked and has a varied playback level.

4. In the masking sound generation system according to claim 1, The control unit generates a natural ambient sound corresponding to the level or frequency characteristics of the sound to be masked as the additional masking sound, in a masking sound generation system.

5. In the masking sound generation system according to claim 1, The control unit generates a masking sound as an additional masking sound, characterized by producing a natural environmental sound whose frequency characteristics are altered in accordance with the fluctuations in the frequency characteristics of the sound to be masked.

6. In the masking sound generation system according to any one of claims 3 to 5, The control unit generates the natural ambient sound within a predetermined range, making it a masking sound generation system.

7. In the masking sound generation system according to any one of claims 3 to 5, The control unit generates a sound by adding an ultra-high frequency sound to the natural environmental sound as the additional masking sound, making it a masking sound generation system.

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