Alvin D Heindel

US Patent:

52315428, Jul 27, 1993

Filed:

Jan 23, 1991

Appl. No.:

7/644626

Inventors:

Alvin D. Heindel - College Park MD

International Classification:

G11B 502

US Classification:

360 29

Abstract:

The present invention relates to a method and device for recording the low frequency band of an audio signal on an amplitude modulated carrier above the highest frequency component of the audio signal. The carrier frequency is at least 19 kHz and is recorded at an adequate level above the noise floor typically about 10 to 30 dB below peak level. The audio signal with the low frequency band optionally attenuated or omitted is directly recorded in the normal audio region on the same track with the corresponding AM carrier. During playback the amplitude modulated carrier is recovered using a highpass or bandpass filter, demodulated and the low frequency signals mixed with the audio. When applied to audio tape reproduction, the present invention improves bass response as compared to direct recording alone. High quality low noise tape and narrow bandwidth of the AM signal allows audio reproduction with high signal to noise ratio. The invention is a further improvement over techniques using an FM carrier recorded in the ultrasound region.