Accuracy increasing in sound pressure level determination from room impulse response

The sound pressure level (SPL) of the maximum length sequence (MLS) signal can be obtained by integration over the squared room impulse response from zero to infinity. However, this integration in practice is performed over a finite impulse response leading to the inaccuracy in SPL determination. In order to analyse the mentioned accuracy, the influence of finite upper limit of integration and noise is investigated using impulse responses generated by simulation and measured responses. The results show that an acceptable accuracy of the SPL for response with sufficiently small noise floor (below -20 or -15 dB) is obtained if the integration upper limit is placed at T/3 or T/4. For the response with the bigger noise floor it would be better to set an upper limit at the knee or, for even better accuracy, at the point somewhat before the knee, here called optimal upper limit.