Tone reduction circuit for headsets

Abstract

A tone reduction circuit for headsets designed to attenuate high frequency signals while permitting low frequency signals to pass undistorted. Input signal is supplied to a low-pass filter, a high-pass filter and an automatic gain control circuit (AGC). Outputs from both filters are input to a comparator, with the comparator output connected to the gain control input of the AGC. The AGC is configured to attenuate only the higher frequency signals. Thus, the comparator output controls gain imparted to the output signal produced by the AGC. The comparator output signals no gain in the automatic gain control circuit when low-pass filter output is greater than high-pass filter output, but when the high-pass filter output is greater than the low-pass filter output the comparator controls the automatic gain generator to attenuate the higher frequency input signal in proportion to the difference between high-pass filter output and low-pass filter output. Attenuation is further enhanced by having a low-pass filter with a shifting break point which is responsive to the comparator output. The low-pass filter break point is shifted down as the comparator output increases in amplitude, thereby further attenuating the input signal.