The internal noise calculator can be used to estimate internal noise levels in a room from a measured external noise level. The calculation is based on BS EN 12354-3 – Estimation of acoustic performance of buildings from the performance of elements, and accounts for transmission losses of walls, windows and doors.
The following formula is used to estimate the internal noise level:
L2 = L1 – R + 10log(S) – 10log(A)
L2 = Sound pressure level in receiving room (dB)
L1 = Sound pressure level 1m from the facade (dB)
R = Sound reduction index (dB)
S = Element area (m2)
A = Total absorption equivalent area in receiving room (m2)