The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 09, 1993
Filed:
Dec. 11, 1990
Ray M Dolby, San Francisco, CA (US);
Stanley G Cossette, San Francisco, CA (US);
Other;
Abstract
Three related embodiments of audio signal dynamic range circuits for consumer and semi-professional audio signal compressors, expanders, and compressor/expander noise reduction systems incorporate certain basic features of professional Spectral Recording (SR) while adapting SR for use with consumer recording media (particularly audio cassette tape) and reducing the cost and complexity of the SR circuitry. In addition, the three embodiments, and particularly the preferred embodiment, provide substantial compatibility with the existing B-type and C-type consumer and semi-professional noise reduction systems. Subjective performance substantially equivalent to 16-bit PCM audio systems is achieved with analog audio cassette tape media. In all three embodiments there are two cascaded stages: (1) a high-level stage having a high-frequency fixed-band/sliding band action-substitution sub-state and a low-frequency fixed-band sub-stage and (2) a low-level stage having only a high-frequency fixed-band/sliding band action-substitution sub-stage. The dynamic action regions of the high-frequency action-substitution sub-stages are staggered. Each of the high-frequency sub-stages provides up to 12 dB of dynamic action (together providing up to 24 dB of dynamic action) and operates in a frequency band defined by a single-pole filter having a high-pass shelving response with a corner frequency of 400 Hz. The low-frequency sub-stage provides up to 10 dB of dynamic action and operates in a frequency band defined by a single-pole filter having a low-pass shelving response with a corner frequency of 200 Hz. The single-pole filter characteristics provide a broad and smooth overlap of the high-frequency and low-frequency characteristics. Particular forms of spectral skewing and antisaturation enhance the performance of the circuits with consumer recording media.