Research On Noise Of Air Conditioner Based On Indoor Sound Field Theory

Excessive air-conditioning equipment noise would adversely affect indoor staff. Atpresent, sound pressure level (SPL) of air conditioner noise is obtained in anechoicchamber, and it is not equal to the SPL of a specific architectural interior. Because thenoise in an anechoic chamber includes only direct sound, but the noise in a specificarchitectural interior includes both direct sound and reverberant sound. Therefore,figuring out the distribution and composition of indoor air conditioner noise, especiallyhow the reverberation impact air conditioner noise，can not only provides the basis foramendments to the noise standard of air-conditioning equipment, but also providesreference for practical noise control engineering.The characteristics of air conditioner noise have been discussed in this paper. Firstof all, the air conditioning noise in a single-person office was tested, on the one hand tounderstand the characteristics of indoor noise distribution, on the other hand to solveindoor sound field, and then the SPLs of both direct sound and reverberant sound wereobtained by calculating. Secondly, indoor sound field in three different sized roomswere comparative studied to get the increase value of air conditioner noise caused byreverberant noise. Finally, indoor sound field with multiple sound sources wasconsidered, the purpose is to get the difference between laboratory noise and two typicalindoor noise, which were considered as maximum and minimum of indoor noise.①Air conditioner noise inside a room was not all the same. The noise at1meteror less close to the wall was higher than other places, the amount of difference is3-4dB(A). The noise intensity of testing point decreases in both longitudinal and transversedirections when the distance between sound source and testing point increases. As thedistance increases, the rate of decline was slow down.②Indoor sound field of single-person office air conditioner was calculated bynonlinear solution. The result showed that both direct sound and reverberant soundmade contribution to total noise in the area near sound source, but only reverberantsound made contribution to total noise in the area far away from sound source. Therewas a critical distance where reverberant sound is10dB(A) higher than direct sound.All critical distances in different situation were less than the length of the room.③Noise added values in the nearest testing point, which caused by reverberation,was named as ΔLp. And ΔLp values ranged from1.9to3.2dB(A) in four wind speed gear. The values of ΔLp,obtained by the comparative experiments of threerooms, ranged from2.6to3.9dB(A). The value of ΔLp in small room was higher thanthat in big room, and showed that reverberation in small room was more influential thanthat in big room.④After taking two factors, room size and the number of sound source, intoconsideration, ΔLp of floor-standing air conditioner ranged from2to5dB(A), and itapproaches the range from3to4dB(A) when both room size and the number of soundsource increase. Correspondingly, ΔLp of embedded and ceiling air conditioner rangedfrom4to7dB(A), and it approaches the range from5to6dB(A) when both room sizeand the number of sound source increase. ΔLp of embedded and ceiling air conditioneris about2dB(A) higher than floor-standing air conditioner under the same conditions.