PNC - the Preferred Noise Criterion

A noise measurement system for continuous or ambient noise in indoor environments. The Preferred Noise Criterion (PNC) is used to judge the acceptability of ventilation and other background broad band noise sources by comparing measured sound pressure levels at different frequency bands against established PNC curves.

PNC	31.5 Hz	63.0 Hz	125 Hz	250 Hz	500 Hz	1000 Hz	2000 Hz	4000 Hz	8000 Hz
PNC - 15	58	43	35	28	21	15	10	8	8
PNC - 20	59	46	39	32	26	20	15	13	13
PNC - 25	60	49	43	37	31	25	20	18	18
PNC - 30	61	52	46	41	35	30	25	23	23
PNC - 35	62	55	50	45	40	35	30	28	28
PNC - 40	64	59	54	50	45	40	35	33	33
PNC - 45	67	63	58	54	50	45	41	38	38
PNC - 50	70	66	62	58	54	50	46	43	43
PNC - 55	73	70	66	62	59	55	51	48	48
PNC - 60	76	73	69	66	63	59	56	53	53
PNC - 65	79	76	73	70	67	64	61	58	58