Apparatus for selective noise suppression for hearing aids

An improved sound amplifying apparatus of the type which includes transducer means for converting sound signals into electrical signals, amplifying means, and means for audibly reproducing electrical signals, wherein the improvement is a selective signal level suppression circuit, the suppression circuit comprising:

• manually adjustable attenuating means responsive to electrical signals from the transducer means for selectively attenuating the transducer electrical signals;
• and
• automatic signal level control means, responsive to the attenuated transducer signals and to amplified signals from the amplifying means, for supplying the attenuated transducer signals to the amplifying means for amplification;
• the automatic signal level control means having means for limiting the level of the attenuated transducer signal which are supplied to the amplifying means to maintain the level of the amplified attenuated transducer signals from the amplifying means at no greater than a predetermined threshold value, whereby adjustment of the attenuation provided by the manually adjustable attenuating means modifies the response of the signal level suppression circuit to the transducer electrical signals by altering the magnitude required in the transducer electrical signals before level limiting of the attenuated transducer signal will occur in the automatic signal level control means.