JPS62138897A - Masking sound system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field This invention is applicable to sounds that occur intermittently or suddenly in relatively quiet places (for example, offices, washrooms, etc.), Audio that you do not want a third party to hear (
The present invention relates to a masking sound method suitable for use in cases where it is difficult for a third party to hear unwanted sounds (herein referred to as unnecessary sounds).

(B) Background Art and Problems Generally, methods for making unnecessary sounds difficult to hear include methods of shielding unnecessary sounds such as in a soundproof room or attenuating sound waves using sound-absorbing materials.

However, these methods are expensive, require a large amount of time and space for installation work, and lack simple practicality.

(...) Purpose of the Invention In view of the above, the present invention provides a masking sound that makes unnecessary sounds difficult to hear in a simple and extremely economical manner, and that causes very little discomfort to surrounding third parties. It provides a method.

(D) Summary of the Invention This invention is capable of producing hundreds of Il at a rate of several to several tens of times per minute.
A synthesized sound of modulated band noise and white noise with a continuous band shift between z and several K fiz is started. Masking sound is generated continuously for about 1 minute with one operation of the switch, making it unnecessary. Makes it difficult to hear sounds.

(e) Example Hereinafter, an example of the present invention will be described in detail based on FIGS. 1, 2, and 3.

First, let me explain the basic principle of this invention. 3. When you are on a moving train, it may be difficult to hear what the other person is saying, or the roar of a jet plane may drown out the sounds you hear. be. This phenomenon is generally called auditory masking, meaning that the sound is masked by the noise.

To express the degree of masking, the minimum audible range of the masked sound (such as conversation) when the masking sound (such as plaster) is present, and the minimum audibility of the masked sound when there is no masking sound and it is quiet. It is expressed as the difference in sound pressure level from the audible limit, that is, the amount of movement of the minimum audible limit, and this is called the masking amount.

Here, to explain with reference to Fig. 1, the sound to be masked is a pure tone of 4001 (z) with a sound pressure level of 80 dB,
) represents the amount of masking when the frequency of a pure tone to be masked with a sound pressure level of 80 dB is shifted. The amount of masking is effective near the frequency of the sound to be masked, and the existing effect is reduced at frequencies distant from that frequency.

Next, curve (2) shows the amount of masking due to narrow band noise with a sound pressure level of 80 dB, a center frequency of 410) 1 z, and a bandwidth of 90 Hz.
It is about 20 dB worse than 1).

For curve (3), the sound pressure level is 80 dB and the bandwidth is 10.
K) Indicates the amount of masking by white noise of Iz,
A large masking effect can be obtained at high frequencies.

Among the sound sources having these characteristics, the present invention adds white noise to narrow band noise.
This provides an extremely effective masking effect as shown in (4).

FIG. 2 is a block diagram showing its configuration, and the band noise generator (5) is configured to pass white noise through a narrow band pass filter to obtain a desired narrow band noise, and to generate another white noise. The mixer (9) combines the white noise from the mixer (8) and the white noise from the mixer (9). The power of this signal is amplified by an amplifier, and a masking sound is generated by a loudspeaker.

As a result of experiments, the inventor found that although the masking effect is excellent, it feels unnatural to synthesized sounds that occur continuously. In order to solve this problem, we devised a method to eliminate the unnatural feeling by moving the center band of the band noise. It has been confirmed through experiments that it is natural for the central band of band noise to move at a rate of several times per minute. However, it has been found that depending on the user's preference, there are cases where the movement speed is faster, several tens of times per minute, so the speed of center band movement can be changed with a switch or continuously adjusted with a variable resistor. It is also good to do.

Therefore, a center band modulator (6) and a modulation frequency switching adjuster (7) are provided to shift the center band of the band noise.

The power supply unit (12) supplies power to all the circuits, but since it is not necessary to operate the device continuously, it is a power-saving type starter that generates a masking sound for a certain period of time and then turns off the power for automatic fishing. A system including a switch (13) is preferable.

FIG. 3 shows an example of how to use the device using the masking sound method according to the present invention. When masking a telephone conversation, (14) is the transmitter, (15) is the transmitter, (16) is the device using this method, and (17) is the third party who does not want the transmitted content to be overheard. be.

For example, a device (16) of this method is installed between a speaker (14) and a third party (17) at a distance as shown in FIG.
By activating the starter switch (13), the voice of the speaker is clearly transmitted to the transmitter, but it creates a masking effect for a third party (17), making it difficult to hear, and reducing band noise. By moving the center band, you will not feel the discomfort of the masking sound.

(f) Effects of the Invention As described above (according to the present invention, by using a synthesized sound of narrow band noise and white noise and moving the center band of the narrow band noise at a rate of several times per minute, Effective masking allows noise to be generated without causing discomfort.

[Brief explanation of drawings]

Fig. 1 is a curve diagram showing the masking effect of an embodiment of the present invention, Fig. 2 is a block diagram showing the configuration of an embodiment of the invention, and Fig. 3 is an explanation showing how to use the embodiment of the invention. It is a diagram. (1) is a curve showing the masking effect of pure tones, (2)
is a curve showing the masking effect due to narrow band noise, (3) is a curve showing the masking effect due to white noise, (・1) is a curve showing the masking effect according to the present invention, (5) is a band noise generator, (6 ) is a band noise center band modulator, (7) is a modulation frequency switching adjuster,
(8) is a white noise generator, (9) is a mixer, (1
0) is an amplifier, (11) is a loudspeaker, (12) is a power supply section,
(13) is a starting switch, (14) is a transmitter, (I5) is a transmitter, (16) is a device of this system, and (17) is a third party. Representative Patent Applicant: Tadashi Nakamura - J1 Zheng Dongbutsu

Claims (1)

[Claims] Several hundred Hz to several KHz at a rate of several to dozens of times per minute
A masking sound method that uses a composite sound of modulated band noise and white noise that undergoes a continuous band shift between the bands to block out unnecessary sounds.