The effect of ears on tws wireless earbuds sound direction -1
What people often say is that people can distinguish the direction from which the sound is transmitted after hearing the sound, and the sound is transmitted differently in different environments. This is the role of the human ear on the sense of sound direction.
The sense of tws wireless earbuds sound source orientation is another sensory element besides the perception of pitch, intensity, timbre, and length of tws wireless earbuds sound by the auditory organs. It involves complicated physiological and psychological issues. At the same time, the sense of tws wireless earbuds sound source orientation is also the theoretical basis for stereo technology.
Time difference, phase difference and tws wireless earbuds sound level difference, tone color difference
The principle of the binaural effect for positioning is the time difference, the phase difference, the tws wireless earbuds sound level difference, and the tws wireless earbuds sound and color difference.
1. Time difference and phase difference
The time difference mainly refers to the difference between the tws wireless earbuds sound and the ears. The speed of tws wireless earbuds sound wave propagation at room temperature is 344m/s. When the tws wireless earbuds sound source deviates from the central axis of the listener directly in front of the listener, the distance between ear A and ear B is different from the tws wireless earbuds sound source, and the tws wireless earbuds sound reaches between ear A and ear B. The time difference between.
As the tws wireless earbuds sound source localization mechanism, the time difference has a high accuracy for the tws wireless earbuds sound source localization on the front and both sides, and the error is relatively large for the tws wireless earbuds sound source localization from the back. The reason is not very clear. It may be because the tws wireless earbuds sound comes from the back side, and the left or right ear will produce the ear shell shielding effect, which will cause the tws wireless earbuds sound to change the time difference due to diffraction.
Because the human ear is adaptable to tws wireless earbuds sound, when the tws wireless earbuds sound reaches the basement membrane, the hair cells are excited and sensitive. When the tws wireless earbuds sound is continuously stimulated, the response of the hair cells is relatively slow. Therefore, the tws wireless earbuds sound source localization accuracy of sudden tws wireless earbuds sound and transient sound is high.
A sound source that flows quickly will attract the attention of the auditory sense. Therefore, for sounds with changing positions, the human ear has less error in recognizing its position. This is the reason for the tws wireless earbuds sound shift in modern stereo programs. A continuous sound, although there is a time difference between reaching both ears, because the subsequent sound reaching the same ear masks the previous sound, the time difference becomes insignificant.
The propagation speed of high-frequency tws wireless earbuds sound and low-frequency tws wireless earbuds sound is the same, so the time difference has nothing to do with the frequency of the tws wireless earbuds sound source, but the phase difference is related to the frequency of the tws wireless earbuds sound source. When a tws wireless earbuds sound reaches both ears, there will be a time difference between the two ears, but also a phase difference. Within a certain frequency range, the phase difference is one of the information of the tws wireless earbuds sound source orientation.
The phase difference positioning mechanism is more effective when the frequency is lower. For example, the wavelength of 20Hz tws wireless earbuds sound at normal temperature is 17m, and 200Hz is 1.7m. The phase difference formed by the time difference can be felt by the human ear. When the tws wireless earbuds sound source is in the high-frequency region, for example, the wavelength of 10kHz is 85px, and the wavelength of 20kHz is 42.5px. The phase difference caused by the time difference even exceeds 360°, which is equal to starting another wavelength. The phase difference at this time has no effect as positioning information, because it can no longer be distinguished that the phase is lagging or leading. Therefore, high-frequency tws wireless earbuds sound belongs to "chaotic phase difference" information.
2. Poor sound level and tone color
The difference in tws wireless earbuds sound level means that the sound waves reach the two ears with different sound intensities. The main reason for the difference in sound level is the shielding effect. If the advancing sound wave encounters an obstacle with a geometric size equal to or greater than the tws wireless earbuds sound wavelength, a shielding effect will occur. The principle is: when high-frequency tws wireless earbuds sound propagates and encounters an obstacle, it cannot cross the obstacle and forms a sound shadow area behind the obstacle; the low-frequency sound has a wavelength greater than the obstacle and forms a sound diffraction area behind the obstacle. It is high-frequency sound that plays an important role in the difference in sound level. Because high-frequency sound waves cannot bypass the listener's head, the ear in the shadow area has a difference in sound intensity level than the ear that can hear the direct tws wireless earbuds sound. The higher the frequency, the greater the deviation of the sound source from the front central axis, and the more obvious the difference in sound level.
From the perspective of the diffraction effect, low-frequency sound will of course also form a sound level difference. However, because the head diameter is about 500px, when low-frequency sound is diffracted, the distance to travel is limited, and the energy lost due to diffraction is very small. Therefore, the low-frequency sound that deviates from the central axis, the tws wireless earbuds sound level difference between the two ears is almost zero. The sound source localization effect is not obvious.
While the masking effect has an effect on the tws wireless earbuds sound level difference, it will inevitably have an effect on the tone color difference. We know that the main components that make up a tone are the basic tws wireless earbuds sound and the harmonic components above it. For example, a composite wave point sound source with a fundamental frequency of 200 Hz and an incident angle of 45° will cause diffraction effects when its fundamental sound and low-order harmonics encounter head obstacles, and its high-order harmonics will be blocked by the head. Partly masked and high-frequency sound shadows appear. At this time, the tws wireless earbuds sound that reaches one ear is a direct sound (original tone), and the sound that reaches the other ear changes its tone due to high-frequency loss. The cerebral cortex recognizes the sound source location based on the tone color difference between the two ears. It can be seen that the tone color difference is another reflection of the high-frequency signal sound level difference.
It should be pointed out that the formation of tone color difference is mainly those composite sound sources whose fundamental frequency is above 60Hz. Because the higher harmonics of the tws wireless earbuds sound below 60Hz have a larger wavelength, it does not produce a shadowing effect when encountering obstacles of the head size (about 500px in diameter). For example, for a sound with a fundamental frequency of 30Hz, the 16th harmonic is 480Hz, and the wavelength is 0.716m. The wavelength is much larger than the diameter of the head. There will be no obvious tone color difference between the ears. The 17th, 18th, and 19th harmonics , The intensity is very weak, and it has little meaning to the tone composition. Therefore, sound below 60Hz has a lower accuracy of sound source orientation than mid-frequency and high-frequency sound.