PNC - the Preferred Noise Criterion

A noise measurement system for continuous or ambient noise in indoor environments.

Preferred Noise Criterion Curves - PNC - is a noise measurement system for continuous or ambient noise in indoor environments proposed by Leo Beranek in 1971.

PNC is often used to judge the acceptability of ventilation and other background broad band noise sources.

Preferred Noise Criterion Curves - PNC - was introduced as a modification of the Noise Criterion - NC due to unacceptable low frequency noise in air-conditioning systems. The PNC at lower frequencies is more stringent than NC.

PNC - Preferred Noise Criterion - Maximum Sound Pressure Level *(dB)*
PNC	Center frequency (Hz)
PNC	31.5	63.0	125	250	500	1000	2000	4000	8000
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

PNC-type criteria provide no protection for low frequency sound exposure, and further, tend to rely on the public's increasing toleration of background noise and what seems to be decreasing auditory skills.

PNC - Preferred Noise Criterion diagram

Download and print PNC chart

Preferred Noise Criterion - PNC - Calculator

Example - Estimating PNC - Preferred Noise Criterion

The Preferred Noise Criterion - PNC - of a noise spectrum like

31.5 Hz : 40 dB
62.5 Hz : 40 dB
125 Hz : 50 dB
250 Hz : 55 dB
500 Hz : 60 dB
1000 Hz : 50 dB
2000 Hz : 55 dB
4000 Hz : 45 dB
8000 Hz : 45 dB

can be estimated to

PNC = 57 dB

as indicated in the diagram below.

PNC - preferred noise criteria - example