13 laws and effects in sound tuning technology

- Jun 19, 2020-

If the time length of sound exceeds about 300ms, the increase or decrease of the time length of sound has no effect on the threshold change of hearing. The perception of tone is also related to the length of the sound. When the sound lasts for a short time, you can't hear the tone. You just hear a click. Only when the sound lasts for more than tens of milliseconds can the feeling tone be stable. Another subjective feeling characteristic of time domain is echo.

3. Subjective sense of space domain

Compared with single ear, double ear has obvious advantages, such as high sensitivity, low hearing valve, directional sense to sound source, and strong anti-interference ability. Under stereo condition, the sense of space obtained by listening to sound through speakers and stereo headphones is different. The sound heard by the former seems to be located in the surrounding environment, and the sound heard by the latter is located in the interior of the head. In order to distinguish the two sense of space, the former is called orientation and the latter is called positioning.

4. Weber's law of hearing

Weber's law shows that there is a direct proportion between the number of objective stimuli and the subjective perception of human hearing sound. When the sound is small and the amplitude of sound wave is increased, the volume of subjective feeling of human ear increases greatly; when the sound intensity is large and the amplitude of sound wave is increased, the volume of subjective feeling of human ear increases less.

According to the above listening characteristics of human ear, the exponential potentiometer is required to be used as the volume controller in the design of volume control circuit, so that when the potentiometer handle is rotated evenly, the volume is increased linearly.

5. Ohm's law of hearing

The scientist ohm discovered Ohm's law in electricity. At the same time, he also discovered Ohm's law in human ear's hearing. This law reveals that the hearing of human ear is only related to the frequency and intensity of each voice, but not to the phase between each voice. According to this law, the control of recording, playback and other processes in the sound system can be done without considering the phase relationship of each seperation in the complex sound.

The human ear is a frequency analyzer, which can separate the harmonics in the polyphony. The resolution sensitivity of the human ear to the frequency is very high. At this point, the resolution of the human ear is higher than that of the eye. The human eye cannot see all kinds of color light components in the white light.

6. Masking effect

Other sounds in the environment will make the listener's hearing of a certain sound decrease, which is called masking. When the intensity of one voice is much higher than that of the other, when it is large enough and the two voices exist at the same time, people can only hear the voice, but can not perceive the existence of the other voice. The amount of masking is related to the sound pressure of masking sound. The amount of masking increases with the increase of the sound pressure level of masking sound. In addition, the masking range of low frequency sound is larger than that of high frequency sound.

This auditory characteristic of human ear provides an important inspiration for the design of noise reduction circuit. In tape playback, we have the experience of listening. When the music program changes continuously and the sound is loud, we will not hear the background noise of the tape. When the music program ends (blank tape), we can feel the "hissing" of the tape Noise is present.

In order to reduce the influence of noise on program sound, the concept of signal-to-noise ratio (SN) is put forward, that is, the signal strength is required to be large enough than the noise strength, so that the existence of noise will not be felt in listening. Some noise reduction systems are designed by using the principle of masking effect.

7. Binaural effect

The basic principle of the binaural effect is as follows: if the sound comes from the front of the listener, the time difference (phase difference) and timbre difference between the sound and the left and right ears are zero due to the same distance between the sound source and the left and right ears. At this time, the sound is felt from the front of the listener instead of leaning to one side. When the sound intensity is different, the distance between the sound source and the listener can be felt.

8. Haas effect

Haass's experiment proves that when two sound sources are in the same time, according to the different time delay between one sound source and the other, the perception of binaural hearing is different. It can be divided into the following three situations to explain:

(1) When the time delay between one sound source and the other is within 5-35ms, it is as if two sound sources are combined into one. The listener can only feel the existence and direction of one sound source ahead of the other, and can not feel the existence of another sound source.

(2) If one sound source delays another 30-50ms, the existence of two 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 for 50ms, the simultaneous existence of two sound sources can be felt, the direction is determined by each sound source, and the lagging sound is a clear echo.

Haas effect is one of the foundations of stereo system orientation.

9. Lloyd's effect

Lloyd's effect is a kind of psychoacoustic effect in stereo range. Lloyd's effect reveals that if the delayed signal is superimposed on the direct signal in reverse phase, there will be an obvious sense of space. The sound seems to come from all directions, and the listener seems to be in the band.

10. Keyhole effect

The mono recording and playing system uses a microphone to record the signal on a track, and uses an amplifier and a loudspeaker when playing the sound. Therefore, the playback sound source is a point sound source, just like the listener listens to the symphony in the room through the keyhole on the door, which is the so-called keyhole effect.

11. Bathroom effect

When you are in the bathroom, you have a personal feeling. The sound produced in the bathroom reverberates for too long and excessive time. This phenomenon is called the bathroom effect in the sound quality description of electroacoustic technology. When the low and medium frequency are exaggerated, there is resonance, the frequency response is uneven, and the 300Hz is raised excessively, the bathroom effect will appear.

12. Doppler effect

Doppler effect reveals the related listening characteristics of mobile sound: when there is relative movement between the sound source and the listener, it will feel that the tone of the sound determined by a certain frequency has changed. When the sound source approaches the listener, it is a tone with a slightly higher frequency. When the sound source leaves, it is a tone with a slightly lower frequency. The variation of this frequency is called Doppler shift. The intensity of the moving sound source is higher when it is the same distance from the listener than when it is not moving, and the intensity of the moving sound source is smaller, usually the sound source is concentrated in the moving direction.

13. Li Kai test

Li Kai's experiment shows that when the phase of the two sound sources is opposite, the sound image can exceed the two sound sources and even jump behind the listening sound.