Subband-based acoustic shock limiting algorithm on a low-resource DSP system

Acoustic Shock describes a condition where sudden loud acoustic signals in communication equipment causes hearing damage and discomfort to the users. To combat this problem, a subband-based acoustic shock limiting (ASL) algorithm is proposed and implemented on an ultra low-power DSP system with an input-output latency of 6.5 msec. This algorithm processes the input signal in both the time and frequency domains. This approach allows the algorithm to detect sudden increases in sound level (time-domain), as well as frequencyselectively suppressing shock disturbances in frequency domain. The unaffected portion of the sound spectrum is thus preserved as much as possible. A simple ASL algorithm calibration procedure is proposed to satisfy different sound pressure level (SPL) limit requirements for various communication equipment. Acoustic test results show that the ASL algorithm limits acoustic shock signals to below specified SPL limits while preserving speech quality.