Subjective perception in the frequency domain
The most important subjective sensation in the frequency domain is tone. Tones like loudness are also a subjective mental quantity of hearing. It is the attribute of hearing to determine the level of the sound.
The difference between a tone in psychology and a musical scale is that the former is a pure tone, while the latter is a tone of a compound sound such as music. The tone of a compound sound is not simply frequency analysis, but also the role 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, then the increase or decrease in the duration of the sound has no effect on the threshold change in hearing. The perception of the tone is also related to the length of the sound. When the sound lasts for a short time, no tone can be heard, but a "click" is heard. The longer the sound is, the more the tone can be felt. Only when the sound lasts more than tens of milliseconds can the sensed tone be stable.
Another subjective sensory characteristic of the time domain is echo.
3. The subjective perception of the spatial domain
双 Binal listening with human ears has obvious advantages over single-ear listening. Its high sensitivity, low listening valve, directional sense to the sound source, and strong anti-interference ability. Under stereo conditions, the sense of space obtained with speakers and stereo headphones is not the same. 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. In order to distinguish the two types, 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 perception of the human ear to hear sound is directly proportional to the logarithm of the objective stimulus. When the sound is small and the amplitude of the sound wave is increased, the subjective volume of the human ear is increased; when the sound intensity is large and the same sound wave amplitude is increased, the amount of increase in the subjective volume of the human ear is small.
According to the above-mentioned listening characteristics of the human ear, it is required to use an exponential potentiometer as the volume controller when designing the volume control circuit. In this way, when the potentiometer knob is rotated uniformly, the volume increases linearly.
5. Ohm's law of hearing
The famous scientist Ohm discovered the Ohm's law in electricity. At the same time, he also discovered the Ohm's law in the human ear's hearing. This law revealed that the human ear's hearing is only related to the frequency and intensity of each partial in the sound. The phase between the tones is independent. According to this law, the control of the recording, playback and other processes in the audio system can be done without considering the phase relationship of the partials in the complex sound.
The human ear is a frequency analyzer that can separate the harmonics in the polyphony. The human ear has a high resolution sensitivity to the frequency. At this point, the human ear has higher resolution than the eye. Color light component.
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 the other, and when the two sounds exist to a certain extent, people can only hear the existence of the loud sound, but not 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 the low frequency sound is larger than the masking range of the high frequency sound.
This hearing characteristic of the human ear provides important inspiration for designing noise reduction circuits. In 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. When the music program ends (blank tape), we can feel "咝 ......" noise to the tape exists.
In order to reduce the influence of noise on the program sound, 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 the noise will not be felt when listening. Some noise reduction systems are designed using the principle of masking effects.
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 tone color difference between the sound waves reaching the left and right ears are equal because the distance from the sound source to the left and right ears is equal. Zero. At this time, it feels that the sound comes from the front of the listener, instead of leaning to one side. When the sound is different, you can feel the distance between the sound source and the listener.
8. Haas effect
Haas's test proves that when two sound sources are simultaneously sounding, when the delay amount of one sound source and the other sound source are different, the feeling of listening to the two ears is different, which can be divided into the following three cases to explain :
When the delay between one sound source and the other sound source is within 5 ~ 35ms, it is as if the two sound sources are combined into one. The listener can only feel the existence and direction of the previous sound source. , Can't feel the presence of another sound source.
If one sound source is delayed by another 30 to 50 ms, the presence of two sound sources can already be felt, but the direction is still determined by the leader.
If the delay amount of one sound source is greater than 50 ms for the other sound source, two sound sources can be felt at the same time, the direction is determined by each sound source, and the lagging sound is a clear echo.
The Haas effect is one of the foundations of stereo system orientation.
9. De Poet Effect
The Reed-Boey effect is another basis for stereo system orientation. The experiment of the De Poet effect is: placing the two speakers of the left and right channels, and the listener listens on the symmetrical lines of the two speakers, and feeds the two speakers with different signals. The following conclusions can be obtained:
l If the same signal is fed to the two speakers, that is, the intensity difference ΔL = 0, and the time difference Δt = 0, only one sound is felt at this time, and it comes from the symmetrical line of the two speakers.
l If the intensity difference ΔL of the two speakers is not 0, then the sound will be skewed to the louder speaker. If the intensity difference ΔL is 15dB or more, the sound will come from the louder speaker.
l If the intensity difference ΔL = 0, but the time difference Δt between the two speakers is not 0, at this time, it feels that the sound moves in the direction of the speaker that arrived first. If the time difference Δt is greater than or equal to 3ms, it feels that the sound comes completely from the direction of the speaker that arrived first.
10. Lowe's effect
The Lowe effect is a psycho-acoustic effect in the stereo range. The Lowe's effect reveals that if the delayed signal is superimposed inverse on the direct signal, it will produce a clear sense of space. The sound seems to come from all directions, and the listener seems to be in the band.
11. Keyhole effect
The mono recording and playback system uses a microphone to record, and the signal is recorded on a track. During playback, an amplifier and a speaker are used, so the reproduced sound source is a point source, as if the listener passed the key on the door. Holes listen to symphonies in the room, which is the so-called keyhole effect.
12. Bathroom effect
When you are in the bathroom, you have a personal experience. The sound emitted from the bathroom is too long and excessive. This phenomenon is called the bathroom effect in the sound quality description of electro-acoustic technology. When the low and intermediate frequencies are exaggerated, resonance occurs, the frequency response is not flat, and the 300Hz boost is excessive, the bathroom effect will occur.
13. Doppler effect
The Doppler effect reveals the relevant listening characteristics of moving sounds: when there is relative movement between the sound source and the listener, it will feel that the pitch of the sound determined by a certain frequency has changed, and when the sound source approaches the listener Is a tone with a slightly higher frequency, and a tone with a slightly lower frequency when the sound source is gone. The amount of change in this frequency is called the Doppler shift. Closer sound sources produce greater intensity at the same distance from the listener than when they do not move, while removed sound sources produce less intensity, and usually the sound source is concentrated in the direction of movement.
14.Li Kai test
Li Kai's test proves that when the two sound sources are in opposite phase, the sound image can exceed the two sound sources and even jump behind the listening sound.
The Li Kai test also suggests that as long as the intensity and phase of the two sound sources (left and right channel speakers) are properly controlled, a wide range (angle, depth) of the sound image moving field can be obtained.