Building Services Engineering 5th Edition Handbook

Room acoustics 339
For 125 Hz,
SPL = 55 × 0.87 + 22 dB
= 69 dB
For 250 Hz,
SPL = 55 × 0.93 + 12 dB
= 63 dB
For 500 Hz,
SPL = 55 × 0.974 + 4.8 dB
= 58 dB
For 1000 Hz,
SPL = 55 × 1.0 + 0dB
= 55 dB
For 2000 Hz,
SPL = 55 × 1.015 − 3.5 dB
= 52 dB
For 4000 Hz,
SPL = 55 × 1.025 − 3.5 dB
= 50 dB
For 8000 Hz,
SPL = 55 × 1.03 − 8.0 dB
= 48 dB
These sound pressure levels are compared to the room data in Table 14.8.
The closest approach to the SPL limit for NR 55 occurs at 500 Hz. Check that NR 50 is exceeded.
For 500 Hz,
SPL = 50 × 0.974 + 4.8 dB
= 53 dB
Table 14.8 Noise spectrum in Example 14.8.
Frequency f (Hz) 31.5 63 125 250 500 1k 2k 4k 8k
NR 55 SPL (dB) 92 78 69 63 58 55 52 50 48
Room SPL (dB) 39 44 48 52 55 49 36 33 28