An open window is an example of 100% sound absorption i.e. no reflection, whereas bathrooms have 'hard' reflective surfaces and therefore very low sound absorption properties and the result is multiple reflections and a diffused sound field.
IEC 801-31-01, property possessed by materials and objects of converting sound energy to heat either by propagation in a medium or when sound strikes the boundary between two media Related Terms - listed alphabetically
Sound Absorption Coefficient
is the fraction of sound energy absorbed by a material. Expressed as a value between 1.0, perfect absorption (no reflection) and 0, i.e. zero absorption (total reflection). The value varies with frequency and angle of incidence, determined experimentally - see Sabin and Sabine's equation.
A Sound Absorption Coefficient of 1 = 100% absorption - for example an open window.
a single-number rating system used to compare the sound-absorbing characteristics of building materials. A measurement of the acoustical absorption performance of a material, calculated by averaging its sound absorption coefficients at 250, 500, 1000 and 2000 Hz, expressed to the nearest multiple of 0.05. Passive Sound Absorbers dissipate sound energy as heat.
Reference Sound Absorption
(Ao) when measuring sound insulation between rooms it is common practice to normalize the measured levels to a reference sound absorption of 10 m²
is the sum of sabin absorption due to objects and surfaces in a room, and due to dissipation of sound energy in the medium within the room.
is a unit of sound absorption. A square metre of 100% sound absorbing material has a value of 1 metric sabin. An example of this would be a 1 m² open window. One square foot of 100% sound absorbing material has a value of 1 imperial sabin.
Sabine: Wallace Clement Sabine an American pioneer in architectural acoustics. He derived an expression for the duration T of the residual sound to decay below the audible intensity. The associated sound absorption unit was named after him - sabin without the e.