Self-correcting audio equalizer

An audio equalizer for use in an audio system producing audio frequency sounds in a listening environment, comprising:

• first input means adapted to be responsive to a first audio signal to be equalized,
• output means for providing an equalized audio signal to be used in producing said audio frequency sounds,
• second input means responsive to a second audio signal derived from sounds produced in said listening environment by said audio system, and
• means for, during normal use of said audio system, automatically determining the differences between the frequency versus amplitude characteristics of said first and second audio signals and adjusting the frequency versus amplitude characteristic of said first audio signal in accordance with said determined difference so as to thereby provide said equalized audio signal.

A method of automatically equalizing an audio signal during normal operation of a high fidelity sound reproduction system comprising the steps of:

• providing a first audio signal,
• generating an acoustic signal from an equalized said first audio signal,
• deriving a second audio signal from said acoustic signal,
• determining, during normal operation, the amplitude versus frequency characteristics of both said first and second audio signals, and automatically modifying the frequency versus amplitude characteristic of said first audio signal in accordance with the difference between said determined amplitude versus frequency characteristics of said first and second audio signals to thus provide said equalized first audio signal for use in generating said acoustic signal.

A self-correcting audio equalizer for use in a system wherein an audio signal source provides a first audio signal which is to be reproduced as an acoustic signal by sound reproducing means, comprising:

• means for regenerating a second audio signal from the acoustic signal provided by said sound reproducing means,
• means for separating each of said first and second audio signals into a plurality of frequency components,
• means for comparing the level of each of said frequency components of said first audio signal with the level of the like frequency component of said second audio signal,
• means for automatically adjusting the amplitudes of each of said frequency components of said first audio signal in accordance with the results of the corresponding said comparison, and
• means for combining said amplitude adjusted frequency components to thereby derive an equalized said first audio signal for driving said sound reproducing means.