An audio limiting circuit capable of satisfying frequency dependent limits and
time domain constraints, is disclosed. In one illustrative embodiment, an input node receives an unattenuated input
signal and a
system modeling filter predicts the amount, if any, by which the
sound pressure level that would be generated by an acoustic
transducer in response to the unattenuated input
signal, would exceed one or more predetermined limits. In that embodiment, an energy
detector separates the excess predicted
sound pressure level into one or more frequency bands and calculates the average
acoustic energy associated with each band. A
gain logic block determines an
attenuation factor based on whether one or more of the predetermined limits has been exceeded and the
attenuation factor values are smoothed to minimize abrupt changes to the unattenuated input
signal. A
delay buffer delays the unattenuated input signal values. Finally, in the embodiment described here, the smoothed
attenuation factor values are synchronized with and applied to the delayed input signal values and the resulting attenuated signal is transmitted to an output node and ultimately to one or more acoustic transducers.