BS 8233:2014 · Annex G

Facade level difference calculator

Internal sound level Leq,2 from facade free-field Leq,ff — octave bands 63 Hz to 8 kHz (equations G.1 + G.2). Day and night periods assessed against BS 8233 internal criteria.

Result

LAeq,2 Day · 16 h
—dB(A)
LAeq,2 Night · 8 h
—dB(A)
LAFmax,2 10th noisiest
—dB(A)
Band Hz LAeq,2 Day LAeq,2 Night LAFmax,2

1 · Source spectrum facade free-field Leq,ff per band

Band Hz631252505001k2k4k8k
Leq,ff Day (dB)
Leq,ff Night (dB)
LAFmax 10th (dB)

2 · Room geometry facade and partitioning areas

Window area cannot exceed facade area.

3 · Glazing window sound reduction index Rwi

Band Hz631252505001k2k4k8k
Rwi (dB)

4 · Trickle vent element-normalised Dn,e per BS EN ISO 10140

Band Hz631252505001k2k4k8k
Dn,e single (dB)

5 · External wall sound reduction index Rew

Band Hz631252505001k2k4k8k
Rew (dB)

7 · Receive room absorption equivalent absorption area A

Library values are seed indicative data — confirm against manufacturer datasheets and BS 8233:2014 Annex C before formal use. Octave-band acoustic data varies materially between specific products. Headline pass/fail tests against BS 8233 internal criteria: 35 dB LAeq,16h day for resting / living rooms, 30 dB LAeq,8h night for bedrooms, and 45 dB LAFmax for individual night-time events (the 10th-noisiest typical threshold per BS 8233 + WHO 1999). The calculation method assumes a traffic-shaped source spectrum (Note 4) and applies no facade shape correction.