Acoustics: Sound pressure vs Sound power

Sound power level is the acoustic energy emitted by a source which produces a sound pressure level at some distance. Whilst the sound power level of a source is fixed, the sound pressure level depends upon the distance from the source and the acoustic characteristics of the area in which it is located.

The sound power is what is used in the acoustic calculation. Sound power is the sound generated at the source. Sound pressure is the airborne sound energy received by a receptor. The dBA level is a function of the 1/1 octave band noise levels

The standard is to limit the noise at the receptor to 5dBA below the surrounding sound (referred to often as LA90- It is used to express the background noise level. The background noise is the level which is exceeded for 90% of the time, or put another way, the sound level is only lower than the LA90 for 10% of the time. You could think of the LA90 as a backstop noise level below which the sound rarely goes.). The receptor being the sensitive neighbouring areas such as BR windows. The assessment is based on the day time background noise levels.

If you need to calculate the sound power at a given receptor you should contact an acoustician. To get the final level at the receptor, the radiation directivity factor is first applied to the sound power, the calculation then applies the distance loss in each 1/1 octave band and the louvre losses (of an acoustic enclosure if used). The 1/1 octave band levels at the receptor are then combined via the A-weighting corrections, to give the dBA level at the receptor.

	RXP35	RXM35	RXA35
Sound Pressure level: Cooling – High dBA	48
Sound Pressure level: Cooling – Nom dBA		49	49
Sound Pressure level: Heating – High dBA	48
Sound Pressure level: Heating – Nom dBA		49	49
Sound power level Cooling – Max		61	61
Sound power level Cooling – Night quiet mode		57
Sound power level Heating – Max		60	61
Sound power level Heating – Nom		61	61
Sound power level Heating – Night quiet mode		57
Sound power level – low sound mode – Cooling – Max		60
Sound power level – low sound mode – Cooling – Night quiet mode		55
Sound power level – low sound mode – Heating Max		60
Sound power level – low sound mode – Heating – Night quiet mode		55

The sound pressure data is carried out in an anechoic chamber with a microphone at 1m distance from the fan.

Acoustic Comparison

		Sound pressure (cooling) dBA							Sound power level – low cooling
Indoor Unit	Sound Power dBA	High	Med	Low	Silent	Outdoor Unit	Sound Pressure Cooling -Nominal	Sound Power dBA	Night quiet mode
FTXF20	53	39	33	25	20	RXF20	46	60
FTXP20	55	39	33	25	19	RXP20	46	61
FTXM20	54	41	33	25	19	RXM20	46	59	53
FTXA20	57	39	32	25	19	RXA20	46	59	55
FTXJ20	57	39	32	25	19	RXJ20	46	60	57
FTXF25	54	40	33	26	20	RXF25	46	60
FTXP25	55	40	33	26	19	RXP25	46	61
FTXM25	54	41	33	25	19	RXM25	46	59	53
FTXA25	57	40	33	25	19	RXA25	46	59	55
FTXJ25	57	40	33	25	19	RXJ25	46	60	57
FTXF35	54	43	34	27	20	RXF35	48	61
FTXP35	58	43	34	27	20	RXP35	48	62
FTXM35	58	45	37	29	19	RXM35	47	60	54
FTXA35	60	41	33	25	19	RXA35	49	61	55
FTXJ35	60	41	33	25	19	RXJ35	49	61	57
FTXF42	59	45	36	30	22	RXF42	48	61
FTXM42	60	45	38	30	21	RXM42	48	60
FTXA42	60	45	37	29	21	RXA42	48	62
FTXJ42	60	45	37	29	21	RXJ42	48	63	58
FTXF50	59	43	39	34	31	RXF50	47	61
FTXP50	59	43	39	34	27	RXP50	47	61
FTXM50	60	46	40	33	27	RXM50	48	60
FTXA50	60	46	39	31	24	RXA50	48	62
FTXJ50	60	46	39	31	24	RXJ50	48	63	58
FTXF60	60	45	41	36	33	RXF60	49	63
FTXP60	60	45	40	36	30	RXP60	49	63
FTXM60	60	46	42	37	30	RXM60	48	63
FTXF71	62	46	42	37	34	RXF71	52	66
FTXP71	62	46	42	37	32	RXP71	52	66
FTXM71	60	47	43	38	32	RXM71	47	66
FAA71	61	45	42	40		ARXM71		52
FAA100	65	49	45	41		AZAS100	44	53
FVXM25A	52	38	32	25	20	RXM25	46	59
FVXM35A	53	39	32	25	20	RXM35	49	61
FVXM50A	61	44	38	31	27	RXM50	48	63
FNA25A9	53	33	31	28		RXM25	46	59
FNA35A9	53	33	31	28		RXM35R9	49	61
FNA50A9	56	36	31	30		RXM50R	48	63
FNA60A9	56	36	33	30		RXM60R	48	63
FCAG35B	49	31	29	27		RXM35R9	48	62
FCAG50B	49	31	29	27		RXM50R	49	63
FCAG60B	51	33	31	28		RXM60R	50	64
FCAG71B	51	35	28			ARXM71R	52	65
FCAG100B	54	37	29			AZAS100MV1	53	70	44
FCAG125B	58	41	29			AZAS125MV1	53	71	44
FCAG140B	58	41	29			AZAS140MV1	54	73	44
FBA35A9	60	35	32	29		RXM35R9	46	59
FBA50A9	60	35	32	29		RXM50R9	49	61
FBA60A9	56	30	28	25		RXM60R9	48	63
FBA71A	56	30	28	25		ARXM71R	48	63
FBA100A	58	34	32	30		AZAS100MV1	57	70	44
FBA125A	62	37	35	32		AZAS125MV1	53	71	44
FBA140A	62	37	35	32		AZAS140MV1	54	73	44
FDXM25F9	53	35	33	27		RXM25R9	46	59
FDXM35F9	53	35	33	27		RXM35R9	49	61
FDXM50F9	55	38	35	30		RXM50R9	48	63
FDXM60F9	56	38	35	30		RXM60R9	48	63
						2MXM40A9	46	46
						2MXM50A9	48	48
						2MXM68A9	48	48
						3MXM68A9	48	48
						4MXM68A9	48	48
						4MXM80A9	48	61
						5MXM90A9	52	64
						3MXM352A9