Example

The figure below presents the Sabine sound absorption coefficients in third octave bands for a 40-mm thick rock wool. Measurement were performed by Mickael Duranteau in 2006 [Dur06] at ENTPE (two vertical red lines are reported at frequencies 200 Hz and 2 500 Hz to identified absorption values considered to compute the SAA).

The measured sound absorption coefficient $\alpha_{i}$ per 1/3 octave band are reported in the table below.

From the measurement values above, the SAA is found to be equal to 0.86.

Comments

The Sound Absorption Average should be used with care:

• The frequency range used to compute the SAA is quite limited compared to the human hearing frequency area [20 - 20 000] Hz. In particular, the third octave bands around 4 000 Hz are not used in its computation.
• The third octave values used are equally weighted which does not correspond to the natural sensitivity of sound by a human ear.

Script

% Compute the Sound Absorption Average (SAA)
% from absorption measurements in diffuse field.
%
% Measurements performed on a 40 mm-thick rock wool 
% by Mickael Duranteau during his 'DEUST VAS 2'
% internship at ENTPE in 2006. 
% 
% Commands for the rotation of tick labels are
% borrowed from rotateticklabel.m
%   Written Oct 14, 2005 by Andy Bliss
%   Copyleft 2005 by Andy Bliss
%
% Everything else is copyleft 2006 luc.jaouen@matelys.com
% cf. APMR on the web,
% Standards/SAA
% for more information