The far field is a sound field larger than twice the wavelength. The longest wavelength of the sound wave (that is, at a frequency of 20 Hz) is 17 meters, so for the entire audio range, the sound of more than 34 meters is the far field, and the size reaches the far field. For large rooms, in the case of far sound, the sound can be seen as no interference. For every doubling of the distance, the sound pressure level is attenuated by 6 dB.
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