Ears Effect of 3D audio

If the sound comes from the front of the listener, the time difference (Phase Difference) between the acoustic wave and the right ear is zero because the distance from the sound source to the left and right ears is equal, at this time, you can feel the sound coming from the front of the speaker, rather than leaning towards a certain side.
 

 
When the sound intensity is different, you can feel the distance between the sound source and the speaker [1].
 

 
The "ears effect" principle is very complicated, but simply put, the human ears are located on both sides of the head. If the sound source is not in front of the speaker, it is biased towards one side, the distance from the sound source to the ears is not equal,
 

 
There is a difference between the time when the sound arrives at the ears and the phase. If the human head is at the lateral sound source, there is a shielding effect on one of the ears, so there is a difference in the sound pressure level when the two ears arrive.
 

 
People compare this subtle difference with the auditory experience originally stored in the brain, and quickly respond to identify the location of the sound. 1. the time difference between the two ears. Because there is a certain distance between the two ears, apart from the front and back sounds, there is a time difference when the sound from other directions reaches the ears.
 

 
If the source is right, the sound must first reach the right ear and then to the left ear. The more the sound source is biased towards one side, the greater the time difference. The experiment shows that when the sound source is connected to two ears, the time difference is about 0.62 Ms. 2. Although the distance between two ears is very close, the sound level of the two ears may be different because of the barrier of the head on the sound. If the sound source is left, the left ear is larger than the right ear.
 

 
When the sound source is connected to two ears, the sound level difference can reach about 25 dB. 3. When the sound arrives at the two ears phase difference, the sound is transmitted in the form of waves, and the phase of the sound in different positions in the space is different (unless just one wavelength is separated ). Due to the spatial distance between the two ears, the phase of the acoustic wave reaching the two ears may be different.
 

The drum film in the ear vibrates with the sound, and the phase difference of the vibration becomes a factor for us to determine the sound source azimuth. Of course, the lower the frequency, the more obvious the difference is. 4. Differences between two ears: If a sound is uploaded from a certain direction on the right, it must bypass some parts of the head to reach the left ear. It is known that the diffraction capacity of a wave is related to the ratio of the wavelength to the obstacle scale.
 

 
The diameter of the human head is about 20 cm, which is equivalent to the wavelength of 1700hz sound waves. Therefore, the ability of sound waves with frequencies above Hz to bypass the head is poor, and the attenuation is greater.
 

 
That is to say, the power in the same voice has different capabilities to bypass the head, and the higher the frequency, the greater the component attenuation. Therefore, the tone of the left ear is different from that of the right ear.
 

 
As long as the sound does not come from the Front (or the front), the two ears will hear different sounds, which is also a basis for people to determine the sound source location.
 

 
Currently, speakers in the sound expansion system of the theater auditorium tend to be placed at the top of the slot, which is determined based on the ability to distinguish between the left and right sides of the ears from the vertical directions,
 

 
In this way, the defect that some listeners feel the sound comes from the lateral side caused by configuring the sound set on both sides of the station port is overcome, avoid making the audience clearly feel that the voice sent by the on-site sound is different from the speaker's direct voice.
 

 
Using the "ears effect", we can use the recording technology to record the sound and then play it out with two or more speakers, making it sound like there is a sound source between the speakers, this hypothetical, actually nonexistent sound source is called "Audio and Video ".
 

 
When we listen to an orchestra playing in a stereo broadcast or recording, you can feel that the cello is in front of you, the violin is in front of you, and the trumpet is in the middle .......
 

For an electro-acoustic band, you can also clearly feel that the main instrument comes from different directions. You can clearly distinguish the high and low voices that are broadcast on the left and right audio streams.
 

 
Therefore, the advantage of stereo sound is not only a sense of reality, presence, space, but also a sense of hearing and low noise because the audio and video are separated or changed.
 

 
Sounds in nature are in stereo sound, but if we replay these sounds after recording, amplification, and other processing, all the sounds will be played out from one speaker, this replay sound (compared with the original sound source) is not three-dimensional.
 

 
At this time, as all the sounds are sent from the same speaker, the original sense of space (especially the spatial distribution of the sound group) also disappears. This replay sound is called a single sound.
 

 
If the entire system from record to replay can restore the original sense of space to a certain extent (it is impossible to completely restore), then this replay sound with a certain degree of location level and other spatial distribution features, it is called stereo in audio technology.
 

 
Stereo Sound pickup methods include a/B, x/y, m/s, and Pan pot) standard, imitation head real standard, real head standard, ortf standard, sound field standard and so on.
 

 
In addition to the structure of the headset, the sound field reproduction of the headset is closely related to the selected CD. The real-person head system is a method of Hanging two micro-microphones to pick up the sound signal at the listening and listening ports of the music playing scene. Its effect is similar to the simulation head system.
 

 
If we use a simulated head CD and a real head CD in a stereo headset, we will feel a much better sound field reproduction effect than other CD records.
 

To sum up, the sound field reproduction effect should be achieved in the audio system of the stereo earphone. First, try to select the headset with the ear mask or without the ear mask, for example, akg's k1000 does not destroy the ear shell shape;
 

 
Second, try to use the "Phase Correction Technology" of the Multi-vibration membrane structure of headphones (such as akg k240m, k240df ), these two headphones are also widely used in the radio and television departments;
 

 
Third, try to use the simulation head CD and the real head CD. Unfortunately, there are very few varieties.
 

 
Definition of the in-ear effect when the sound source (including complex cluster signals) is biased towards the left or right ears, that is, the distance from the source to the left and right ears is different when the central axis is located in front of the two ears, this will cause differences in the sound level, time, and phase between the two ears.
 

 
This tiny difference is perceived by the human ears, transmitted to the brain, and compared and analyzed with the existing auditory experience stored in the brain to determine the sound location. This is the ears effect.
 

 
On the stage, use two microphones that are not too far apart, connect them to the two amplifiers respectively, and then connect the changed current after the amplifier is amplified to the two speakers corresponding to the location of the microphone in the other room.
 

 
In this way, when an actor walks from left to right on the stage, the audience in the other room will feel like the actor is singing from left to right in front of himself.
 

 
If two recorders are used to record the audio current sent from two microphones at the same time, and then place the two speakers simultaneously at the same time in the position corresponding to the microphone, the sound you hear will have a good stereoscopic effect, which is a two-channel stereo recording.
 

Currently, most stereo Magnetic recorders use two channels. Both the recording head and the recording head are made of up and down two sets of coils. The core stack thickness of the head is more than half that of the general tape recorder head,
 

 
Magnetic Tracks on tapes are more than half as narrow as those recorded by normal recorders. In this way, there will be four traces on one tape.
 

 
During the recording, after the sound is changed from the two microphones on the left to the right to the audio current, the two amplifiers in the recorder are respectively amplified and sent to the two wire circles of the recording head, when the tape passes through the recording head,
 

 
The two-channel recording is recorded on the two tracks of the tape at the same time. During sound recording, when the tape passes through the sound recording head, the two sets of coils of the sound recording head are respectively induced to change the current of the two traces, which are amplified by the two amplifiers respectively,
 

 
Then, the two speakers arranged in the left and right sides of the listener are used to re-release the sound of two sound channels, so that the audience can gain a stereoscopic effect.
 

 
Test Method of the two ears effect 1. Use a plastic hard pipe (or metal pipe) with a length of 1.5-2.0 m and a diameter of 25mm, and then fill the inside with sand and block the two ends with waste paper, after being heated by a stove, the two tubes are in a circular shape with a distance of about 250mm.
 

 
Ears effect 2. Pour out the fine sand in the pipe, smooth the pipe mouth, and use a cloth to put the pipe on the two ears of the listener.
 

 
As shown in the figure on the right: 3. Close your eyes and ears, and the assistant gently clicks on any part of the tube with a wooden stick. The tester can accurately determine the position of the hitting place, this is the dual-in-ear effect.
 

From: http://zhidao.baidu.com/question/192382939.html