13 Laws and Effects in Sound Tuning Technology

1. Subjective feeling in the frequency domain

The important subjective feeling in the frequency domain is pitch. Like loudness, pitch is also a subjective mental quantity of hearing, which is the attribute of hearing to judge the pitch of sound. The difference between tones in psychology and scales in music is that the former are tones of pure tones, while the latter are tones of complex sounds such as music. The tone of compound sounds is not simply frequency resolution, but also a function of the auditory nervous system, which is influenced by the listener's listening experience and learning.

2. Subjective perception of time domain

If the sound is longer than about 300ms, then the change in the auditory threshold will not be affected by the increase or decrease in the sound length. The perception of pitch is also related to the length of the sound. When the sound is very short in duration, no pitch can be heard, just a "click". The duration of the sound is lengthened to allow the perception of pitch. The perceived pitch is stable only when the sound lasts for more than tens of milliseconds. Another subjective sensory property of the time domain is echo.

3. Subjective perception of spatial domain

The human ear with two ears to listen to sound than with one ear to listen to sound has obvious advantages, its sensitivity is high, the listening valve is low, the sound source has a sense of direction, and has a relatively strong anti-interference ability. In stereo conditions, with speakers and with stereo headphones to listen to the sound to get the sense of space is not the same, the former heard the sound seems to be located in the surrounding environment, and the latter heard the sound position in the head, in order to distinguish between the two kinds of sense of space, the former is called orientation, the latter is called positioning.

4. Weber's Law of hearing

Weber's law states that the subjective perception of a sound by the human ear is proportional to the logarithm of the objective stimulus. When the sound is small and the amplitude of the sound wave is increased, the subjective feeling volume of the human ear increases greatly. When the sound intensity is high and the same acoustic wave amplitude is increased, the volume increase of the subjective perception of the human ear is small.

According to the above of person ear listen to sound characteristic, the requirement uses exponential potentiometer as volume controller when designing volume control circuit, when such uniform rotation potentiometer turns handle, volume is linear increase.

5. Ohm's Law of hearing

Scientist Ohm discovered the Ohm's law in electricity, at the same time he also discovered the Ohm's law in human ear hearing, this law revealed: the human ear hearing is only related to the frequency and intensity of the sound, and the phase between the parts of the sound is not related. According to this law, the control of the recording, playback and other processes in the sound system can be done without considering the phase relationship of each partial tone in the complex sound.

The human ear is a frequency analyzer, which can separate the harmonics in the polyphonic tone. The human ear is very sensitive to the resolution of frequency, and the human ear is higher than the eye in this point, and the human eye can not see the various color light components in the white light.

6. Masking effect

Other sounds in the environment can reduce the listener's ability to hear a particular sound. This is called masking. When the intensity of one sound is much greater than the other, when it is so loud that both sounds are present at the same time, people can only hear the loud sound and cannot perceive the other sound. The amount of masking is related to the sound pressure of masking sound. When the sound pressure level of masking sound increases, the amount of masking increases. In addition, the masking range of low frequency sound is larger than that of high frequency sound.

This auditory characteristic of human ear provides important inspiration for designing noise reduction circuit. In TAPE playback, there is such a sound experience, when the music program is continuously changing and loud, we will not hear the background noise of the tape, but when the music program is over (blank tape), we can feel the tape "hissing..." Noise exists.

In order to reduce the influence of noise on the sound of a program, the concept of signal-to-noise ratio (SN) is proposed. That is, it requires that the signal intensity is large enough to be heard without noise. Some noise reduction systems are designed using the principle of masking effect.

7. Binaural effect

The basic principle of binaural effect is as follows: if a sound comes from directly in front of the listener, the distance between the sound source and the left and right ears is equal, so that the time difference (phase difference) and timbral difference of the sound wave reaching the left and right ears are zero, and the sound is perceived to come from directly in front of the listener, rather than to one side. When the sound intensity is different, the distance between the sound source and the listener can be felt.

8. Haas effect

Haas' experiment proved that: when two sound sources are simultaneously heard, according to the delay amount of one sound source and the other sound source, the two ears' hearing experience is different, which can be divided into the following three cases:

(1) When the delay between one sound source and the other sound source is within 5 ~ 35mS, the listener can only feel the existence and direction of one sound source ahead of the other sound source.

(2) If one sound source delays the other by 30 ~ 50mS, the existence of two sound sources can be felt, but the direction is still determined by the leader.

(3) If the delay of one sound source is greater than that of the other by 50mS, two sound sources can be felt at the same time, the direction is determined by each sound source, and the lag sound is a clear echo.

The Haas effect is one of the bases of stereo system orientation.

9. The Lowe Effect

The Lowe effect is a psychoacoustic effect in the stereo range. The Lowe effect reveals that if the delayed signal is reversed and superimposed on the direct signal, it creates a distinct sense of space, as if the sound is coming from all directions, and the listener is in the middle of a band.

10. The keyhole effect

Mono recording and playback systems use a microphone to record, the signal is recorded on a track, playback using an amplifier and a loudspeaker, so the playback source is a point source, just as the listener listens to the indoor symphony through a keyhole in the door, this is the so-called keyhole effect.

11. The bathroom effect

When THE BODY IS IN THE BATHROOM, THERE IS a PERSONAL EXPERIENCE, THE SOUND THAT COMES OUT INSIDE THE BATHROOM, REVERBERATION TIME IS TOO LONG AND EXCESSIVE, THIS KIND OF PHENOMENON IS called BATHROOM EFFECT in THE sound quality description of electroacoustic technology. Bathroom effect occurs when a certain segment of low and medium frequency is exaggerated, resonance, frequency response is not flat, and 300Hz is lifted too much.

12. Doppler Effect

Doppler effect reveals the auditory properties of moving sound: when there is relative movement between the source and the listener, the tone of the sound determined by a certain frequency will be felt to change, when the source is approaching the listener, it is a slightly higher frequency tone, when the source is leaving it is a slightly lower frequency tone. This change in frequency is called the Doppler shift. A moving sound source at the same distance from the listener produces greater intensity than when it is not moving, while a moving sound source produces less intensity, usually concentrated in the direction of movement.

13. Li kai test

Li Kai test has proved that when the phase of two sound sources is opposite, the sound image can go beyond the two sound sources and even jump behind the listening sound.

Li Kai'S test also SUGGESTS THAT A wide range (Angle, depth) of acoustic image moving field can be obtained as long as the intensity and phase of two sound sources (left and right channel loudspeaker) are properly controlled.