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:
Mar. 13, 2001
Filed:
Jun. 08, 1998
David Dal Farra, Nepean, CA;
Nortel Networks Limited, Montreal, CA;
Abstract
The invention is an audio compression system for reducing distortion arising primarily from excessive loudspeaker excursion. For a given input audio signal, the maximum signal magnitude (or envelope, energy or power) level above which the loudspeaker will begin to distort is dependent upon the frequency content of the signal. In this invention, the input audio signal is filtered and the magnitude (or envelope, energy or power) level of the filtered signal is compared to a single, constant threshold level. The input audio signal is subsequently compressed only if the magnitude (or envelope, energy or power) level of the filtered audio signal exceeds the threshold value. In one embodiment, the filter has a frequency response which models the excursion response of the loudspeaker in question, and which can be obtained analytically for various types of loudspeakers. In another embodiment, the filter has a frequency response which is related to an experimental curve describing the maximum voltage leading to just acceptable distortion as a function of frequency. By attenuating only those signals which cause distortion (due primarily to excessive loudspeaker excursion), efficiency of the audio compression system is improved.