2001

f c

k R T 340 m/s 5000 m/s 3320 m/s 1450 m/s 500 m/s

20 ~ 20000Hz 20 Hz 20000 Hz

2:131.3(31.25)63(62.5)125250500100020004000 8000 Hz

WW IW/m2 pPa

: :

() p0=210-5 PaI0=110-12 W/m2 p=20 PaI=1W/m2

L dB 2105Pa ~ 20Pa

(IPW ) n L1

10 lg2 = 3 dB

10~15 dB

()AE

11

Q R

S arrLpLpLWLWS0f IIV4QAB

1000 Hz Phon

A 4070100ABC AA 40A

A

NR(Noise Rating) A NRISO LA =NR+5 dB

NC NC(Noise Criterion Curves)Beranek19571968ISO NR LA =NC+10 dB NCNR5

PNC PNC(Preferred Noise Curves )NC PNC=3.5+NC

NR(dB)AdB(A) 35~45 40~50 40~45 40~50 35 40 45 50 50~55 55~60 40~45 40~50 30~45 35~50 30 35 25 30 20 25 35 40 35 40

a

25mm25mm

=11.7cm=3.4m

()

Sound Mask 1

2

T

f f 0

0 dB 0 dB? NRNC