JPH06204749A - Fluctuation noise generating method for improving environment - Google Patents

Abstract

PURPOSE:To obtain a pleasant sound without any repetition and changing irregularly without rhythm and melody used for improving a psychoacoustic environment by amplitude-modulating white noise or white noise whose sound quality is adjusted with a nonlinear amplitude signal. CONSTITUTION:A polygonal line gain variable circuit utilizing a nonlinear characteristic of a diode is employed for a nonlinear gain circuit. An output voltage V2 of the circuit is expressed in equation I, where V1 is an input voltage, R1,R2,r are resistors, D is a resistance of a diode, and A is an idealistic operational amplifier. The resistance of the diode varies with the terminal voltage VD of the diode, and the resistance is larger when the terminal voltage of the diode is nearly 0.5V or below, and the resistance is negligible when the terminal voltage of the diode is 1V or over in the case of a silicon diode. Thus, the equation I indicates the output voltage in the case of VD<0.5V, the equation II depicts the output voltage in the case of VD=0.5V, and the equation III shows the output voltage in the case, of VD>1V. As a result when the VD is 0.5-1V, the output voltage is the intermediate value between the voltages expressed in the equations II and III. Then the gain characteristic of the nonlinear gain circuit is expressed by polygonal line approximation having one crossover point and plural crossover points are realized by employing plural numbers of diodes.

Description

Detailed Description of the Invention

[0001]

[Industrial application fields] Audio industry, office equipment related industry, or construction industry for improving living environment.

[0002]

Background Art BGM (Background Music) is a psychoacoustic technique for environmental improvement that has been widely used in the past. Since this method is suitable for giving mental relaxation in relatively monotonous work, it is used in line workshops of mass production plants, etc.
If it does not interfere, it may be used in the office. In a place where BGM is always used, many songs are prepared and played back on a recording tape so that the same song will not be repeated many times.

[0003]

The psychoacoustic environment improvement method using music has an intentional element of music itself, that is, a rhythm and a melody. It may not be an improvement and may hinder the work. On the other hand, there is random noise as a meaningless sound, but this also causes fatigue if constantly emitted in a certain amount. Furthermore, even if noise is intermittently emitted, it becomes a problem if it becomes artificial and unnatural. Therefore, there is no rhythm or melody, and there is no sound, and the sound volume is moderate, and
The challenge is to get a randomly changing sound.

[0004]

In order to solve the above-mentioned problems, the present invention relates to the amplitude of narrow band noise extracted by applying a narrow band filter to white noise or an amount proportional to the amplitude, When the input signal is smaller than a certain value, nonlinear signal processing is performed to output a smaller value to obtain a nonlinear amplitude signal, and the white noise or tone noise adjusted white noise is amplitude-modulated by the nonlinear amplitude signal. The characteristic is the fluctuation noise generation method for environment improvement.

[0005]

The function of the present invention will be described below. The narrow band noise obtained by applying a narrow band filter to white noise (Gaussian noise) becomes a pure tone determined by the center frequency of the narrow band filter if the band width is infinitely narrow. , If the center frequency is F and B is sufficiently smaller than F, then the narrowband noise is at a frequency of almost F,
Its amplitude fluctuates slowly and irregularly at a frequency of about B. The magnitude A of the amplitude (quantity obtained by envelope detection or linear detection) of such narrowband noise
The probability density function of follows the Rayleigh distribution.

When the white noise whose sound quality is adjusted by the amplitude of the narrow band noise is amplitude-modulated, the probability density in the vicinity of A = 0 is much smaller than the probability density of the average amplitude, and in addition, it is usually There is also a problem with the accuracy of the multiplier used as a means for amplitude modulation, and it is not satisfactory from the viewpoint of hearing.

Therefore, the probability density near A = 0 is increased to
In addition, in order to smoothly change the amplitude from large to small and from small to large, non-linear signal processing is performed such that when the input signal is smaller than a certain value, it is output as a smaller value. This processing can be realized by utilizing the nonlinear characteristic of the diode in the analog method, and can be realized by multiplying the amplitude by a coefficient proportional to the amplitude of the input signal in the digital method.

In this way, if the non-linear amplitude signal with the increased probability density near A = 0 is used as the modulation signal and the white noise or the white noise whose sound quality is adjusted is amplitude-modulated,
It is possible to obtain a fluctuation noise for improving the environment, which is meaningless and gradual, which is satisfactory from the viewpoint of hearing, and which randomly fluctuates from a quiet state to an appropriate size.

[0009] If the above-mentioned fluctuation noise is power-amplified and radiated to an office space or the like with an appropriate volume and radiated to an office space or the like, an environmental improvement that does not impede intellectual work and rather provides mental relaxation in which improvement in work efficiency can be expected Is possible.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of an apparatus which implements an environment improving fluctuation noise generating method according to the present invention by an analog method. In FIG. 1, reference numeral 1 is a white noise generator, 2 is a low-pass filter for adjusting the sound quality of white noise to pink noise which is preferable for listening, 3 is a multiplier for amplitude modulation of pink noise, and 4 is white noise. , A narrowband filter for obtaining narrowband noise, 5 is a linear detector for obtaining the amplitude of narrowband noise, 6 is a low-pass filter for removing a steep fluctuation waveform component from the output waveform of the linear detector, 7 Represents a non-linear gain circuit for performing non-linear signal processing.

In the white noise generator of No. 1, noise generated when a current is passed through the diode, noise obtained in a detuned state or noise obtained by wideband detection of input noise using an FM demodulation circuit, etc. Can be used as a white noise source.

2 low pass filters have 3 per octave
It is possible to use one having a characteristic that gives an attenuation of dB.

The narrow band filter 4 has a bandwidth of about 1 Hz.

The low pass filter of 6 has a cutoff frequency of 0.5H.
The thing of about z is used.

As the non-linear gain circuit of 7, a broken line gain circuit utilizing the non-linear characteristic of the diode can be used.
For example, in a circuit as shown in FIG. 2, if V1 is an input voltage, V2 is an output voltage, R1, R2, r are resistors, D is a resistance given by a diode, and A is an ideal operational amplifier,

[Equation 1] Becomes The resistance value of D changes depending on the terminal voltage VD of the diode, and in the case of a silicon diode, it shows a very large resistance value up to about 0.5 volt.
Above a volt, the resistance can be ignored. Therefore,
Equation (1) is as follows. When VD <0.5

[Equation 2] When VD> 1

[Equation 3] When VD is 0.5 to 1 volt, equations (2) and (3)
Although it takes an intermediate value of the equation, as is clear from these results, the gain characteristic of the non-linear gain circuit shown in the example of FIG. 2 is expressed by a polygonal line approximation with one bend. If a plurality of diodes are used, it is possible to realize a nonlinear gain characteristic having a plurality of bends and approximated to a broken line.

An example in which the fluctuation noise generation method for environment improvement of the present invention is implemented by a digital system is shown in a block diagram of FIG. In FIG. 3, reference numeral 1 denotes a white noise generator, which is realized by an analog method. The analog white noise output from the white noise generator is converted into a digital signal by the AD converter 2 and the digital filter 3 is used. The tone quality is adjusted to pink noise, amplitude multiplication is performed in the multiplication unit of 4, and DA conversion is performed in 9 and output as fluctuation noise of the analog waveform. On the other hand, 5 in FIG. 3 is a digital bandpass filter, which obtains narrow band noise,
The absolute value calculation unit of 7 obtains the amplitude component, the digital low-pass filter of 7 removes the steep fluctuation component from the amplitude component, obtains a smooth fluctuation waveform, and the nonlinear signal processing unit of 8 converts it into a nonlinear amplitude signal. , And the modulated signal of the multiplication unit of 4.

The white noise generator 1 can be realized by the same one as in the case of FIG.

The third digital filter is Japanese Patent Application No. 1-
It can be realized by connecting a plurality of digital filters shown in 303329 in cascade.

The digital bandpass filter 5 can be realized by the digital bandpass filter disclosed in Japanese Patent Application No. 1-249048.

The digital low-pass filter of 7 is
This can be realized by a moving average process of the input signal or a digital low pass filter represented by a biquadratic function.

The non-linear signal processing unit 8 outputs the output signal Y (1) obtained by applying the following calculation to the input signals X (1), X (2), ..., X (n) ,. ), Y
(2), ..., Y (n) ,. If X (n) is less than 1,

[Equation 4] If X (n) is greater than 1, then

[Mathematical formula-see original document] That is, the input signal is adjusted to an appropriate size,
A desired nonlinear amplitude signal can be obtained by providing a linear gain when the instantaneous value is greater than 1 and a squared gain when the instantaneous value is less than 1.

[0022]

As a result of realizing and using the device based on the fluctuation noise generation method for environment improvement of the present invention, it was found that pink noise is preferable to white noise with respect to the sound quality of noise. . Regarding the fluctuation cycle, it was confirmed that suppressing a component of 1 Hz or higher has the effect of creating a relaxed atmosphere, and that it is indispensable that there is a moderate silence section in order to give pleasure. As a result of conducting an experiment using the above device,
The effects of the present invention are as follows. 1) In a comparatively quiet conference room, there is no tension and it becomes easier to talk. 2) It has a masking effect on anxious speech from a third party in an office or the like. 3) Helps reduce stress for intellectual work that tends to cause stress.

[0023]

[Brief description of drawings]

FIG. 1 is a block diagram of an analog type fluctuation noise generator according to the present invention.

[Explanation of symbols]

 1 White noise generation 2 Low-pass filter 3 Multiplier 4 Narrow-band filter 5 Linear detector 6 Low-pass filter 7 Non-linear gain circuit

FIG. 2 is a diagram showing a configuration example of a non-linear gain circuit.

[Explanation of symbols]

 V1 input voltage V2 output voltage r, R1, R2 resistance D diode resistance A operational amplifier

FIG. 3 is a block diagram of a digital fluctuation noise generator according to the present invention.

[Explanation of symbols]

 1 White Noise Generator (Analog) 2 AD Converter 3 Digital Filter 4 Multiplier 5 Digital Bandpass Filter 6 Absolute Value Calculator 7 Digital Lowpass Filter 8 Nonlinear Signal Processor

Claims (1)

[Claims] 1. A white noise is output as a smaller value when the input signal is smaller than a certain value in the amplitude of the narrow band noise extracted by applying a narrow band filter or the amount proportional to the amplitude. A method for generating fluctuation noise for environment improvement, characterized in that non-linear signal processing is performed to obtain a non-linear amplitude signal, and white noise or white noise whose sound quality is adjusted is amplitude-modulated by the non-linear amplitude signal.