Low voice-frequency compressor

Abstract

This invention generally relates to audio signal processing apparatus and methods for altering, and particularly increasing, the perceived level of bass frequencies in an audio signal. The apparatus comprises an audio input to receive an audio input signal; a compressor coupled to the audio input and having an output, to compress said audio input signal; a high-cut filter coupled to the output of said compressor to provide a filtered compressor output; and a combiner (206) to combine a signal from said compressor output with a signal from said audio input to provide a combined audio output; and wherein said compressor is configured to distort said audio input signal such that said distortion is perceivable as an increase in the level of bass in said combined audio output.

Description

technical field [0001] The present invention generally relates to audio signal processing. More particularly, the present invention relates to apparatus and methods for altering, and in particular enhancing, the perceived level of bass frequencies in an audio signal. Background technique [0002] Many low-cost headphones and speakers, as well as mid-fidelity audio systems, especially portable systems, typically have poor bass response. However listeners generally desire enhanced bass content, especially when listening to music with strong beats. A number of bass enhancement circuits have therefore been proposed, such as those described in US 5,481,617, US 4,055,818, US 5,509,080, EP0 266 148A and DE 197 42 803A. [0003] FIG. 1 shows a conventional bass enhancement / suppression circuit 100, which can be applied in both analog and digital domains, or a combination of the two. The audio input signal is provided via line 102 to a low pass filter 104 and to an output adder or ...

AI Technical Summary

Problems solved by technology

[0005] The problem with using a bass boost circuit in the digital domain is that when the bass signal exceeds the dynamic range of the digital word it can be overloaded, which will limit the amount of bass boost that can be applied

This problem is solved in the prior art by attenuating the entire signal before applying the bass boost function, but the disadvantage of this technique is that the dynamic range of the signal is reduced, resulting in a lower signal-to-noise ratio

The SNR of a system can be improved by amplifying the signal before it is transmitted through the noisy signal, but this amplification is limited at high levels by the distortion of the channel

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