Propagation of Sound Indoors - the Room Constant

Calculator for sound pressure level in rooms considering direct and reverberant sound, including room constant calculations based on acoustic absorption properties.

Sound Pressure Level Calculator

For a continuing sound source in a room, the sound level is the sum of direct and reverberant sound.

Formula: Lp = LN + 10 log(D / (4π r²) + 4 / R)

Where:

Lp = received sound pressure level (dB)
LN = sound power level from source (dB)
D = directivity coefficient (typical 1 for receivers in middle of room)
R = room constant (m² Sabin)
r = distance from source (m)

Calculator

Inputs

Sound Power Level (LN) (dB)

Directivity Coefficient (D)

Distance from Source (r) (m)

Total Room Sound Absorption (A) (m² Sabin)

Mean Absorption Coefficient (αm)

Results

Room Constant (R)-- m² Sabin

Sound Pressure Level (Lp)-- dB

Room Constant Formula

R = A / (1 - αm)

Or for individual surfaces:

R = Σ(Si × αi) / (1 - αm)

Where:

R = room constant (m² Sabine)
A = total room sound absorption (m² Sabine)
αm = mean absorption coefficient of the room
Si = individual surface area in the room (m²)
αi = absorption coefficient for individual surface