Patent ID: 7577263

Claim:
A sound reproduction system comprising: a digital audio signal input; a digital audio signal processor; a digital audio signal output, a sensor that measures a background noise level, and an element having as an input the measured noise level and as an output a HP cut-off frequency, wherein the HP cut-off frequency increases as the background noise level increases, and a LP cut-off frequency decreases as the HP cut-off frequency increases, and wherein the digital audio signal processor comprises: a high pass (HP) filter, with a HP frequency (f), that filters a signal, an amplifier that amplifies the filtered signal, a low pass (LP) filter, with a LP frequency (f), that filters the amplified signal and provides an output signal, an establisher that establishes either the HP frequency or the LP frequency, and a matcher that matches the HP frequency and the LP frequency of the HP filter and the LP filter respectively to each other.