14 laws of audio technology

There are 14 laws in audio technology, do you know which ones?

1. Subjective perception in the frequency domain

The most important subjective sensation in the frequency domain is tone. Tonal like loudness is also a subjective psychological quantity of hearing. It is the attribute of hearing to judge the level of sound tone.

The difference between tones in psychology and musical scales is that the former is a pure tone, while the latter is a tone of a composite sound such as music. The pitch of the composite sound is not just frequency analysis, but also the function of the auditory nervous system, which is affected by the listening experience and learning of the listener.

2. Subjective perception in the time domain

If the duration of the sound exceeds approximately 300 ms, the increase or decrease of the duration of the sound has no effect on the threshold change of hearing. The perception of tone is also related to the length of time of the sound. When the sound lasted for a short time, the tone could not be heard, just a click. Only when the duration of the sound is longer can there be a feeling of tone. Only when the sound lasts for more than tens of milliseconds can the tone of the feeling be stable.

Another subjective sensory characteristic of the time domain is echo.

3. Subjective perception of the spatial domain

Binaural listening for human ears has obvious advantages over single-ear listening. It has high sensitivity, low listening valve, sense of direction to the sound source, and strong anti-interference ability. In stereo conditions, the spatial sense obtained by listening with the speaker and stereo headphones is different. The sound heard by the former seems to be located in the surrounding environment, while the sound heard by the latter is located inside the head. The sense of space refers to the former as orientation and the latter as positioning.

4. Weber's law of hearing

Weber's law shows that the subjective sensation of the human ear listening to sound is proportional to the logarithm of the objective stimulus. When the sound is small and the amplitude of the sound wave is increased, the volume of the subjective perception of the human ear is increased; when the sound intensity is large and the same sound wave amplitude is increased, the volume of the subjective perception of the human ear is increased.

According to the above-mentioned listening characteristics of the human ear, the design of the volume control circuit requires the use of an exponential potentiometer as the volume controller, so that when the potentiometer knob is rotated evenly, the volume increases linearly.

5. Ohm's law of hearing

The famous scientist Ohm discovered Ohm's law in electricity. At the same time, he also discovered Ohm's law in human ear hearing. This law reveals that the hearing of the human ear is only related to the frequency and intensity of each partial sound in the sound, but to each The phase between the tones is irrelevant. According to this law, the recording, playback and other processes in the audio system can be controlled without considering the phase relationship of the partials in the complex sound.

The human ear is a frequency analyzer, which can separate the harmonics in the polyphony. The human ear has a high sensitivity to frequency resolution. At this point, the human ear has a higher resolution than the eye, and the human eye cannot see the various kinds of white light. Color light component.

6. Masking effect

Other sounds in the environment will reduce the listener's hearing of a certain sound, which is called masking. When the intensity of one sound is much greater than that of another sound, when it is so loud that the two sounds exist at the same time, people can only hear the sound of the sound, but can not perceive the existence of the other sound. The amount of masking is related to the sound pressure of the masking sound. As the sound pressure level of the masking sound increases, the amount of masking increases. In addition, the masking range of low-frequency sounds is larger than that of high-frequency sounds.

This auditory characteristic of the human ear provides important inspiration for the design of noise reduction circuits. In the tape playback, there is such a listening experience. When the music program is continuously changing and the sound is loud, we will not hear the background noise of the tape, but when the music program ends (blank tape), you can feel "Hi ..." noise to the tape exists.

In order to reduce the impact of noise on the sound of the program, the concept of signal-to-noise ratio (SN) is proposed, that is, the signal strength is required to be sufficiently larger than the noise strength, so that listening will not feel the presence of noise. Some noise reduction systems are designed using the principle of masking effect.

7. Binaural effect

The basic principle of the binaural effect is this: If the sound comes directly in front of the listener, then the distance between the sound source and the left and right ears is equal, so the time difference (phase difference) and timbre of the sound waves reaching the left and right ears are Zero, at this time feel that the sound comes from directly in front of the listener, rather than leaning to one side. When the sound intensity is different, the distance between the sound source and the listener can be felt.

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