William Morrell

US Patent:

7013011, Mar 14, 2006

Filed:

Dec 28, 2001

Appl. No.:

10/040922

Inventors:

William A. Weeks - Santa Cruz CA, US
William R. Morrell - Santa Cruz CA, US

Assignee:

Plantronics, Inc. - Santa Cruz CA

International Classification:

H03G 5/00
H03G 3/00
G10L 19/14

US Classification:

381 98, 381107, 704224, 704225

Abstract:

An audio limiting circuit capable of satisfying frequency dependent limits and time domain constraints, is disclosed. In one illustrative embodiment, an input node receives an unattenuated input signal and a system modeling filter predicts the amount, if any, by which the sound pressure level that would be generated by an acoustic transducer in response to the unattenuated input signal, would exceed one or more predetermined limits. In that embodiment, an energy detector separates the excess predicted sound pressure level into one or more frequency bands and calculates the average acoustic energy associated with each band. A gain logic block determines an attenuation factor based on whether one or more of the predetermined limits has been exceeded and the attenuation factor values are smoothed to minimize abrupt changes to the unattenuated input signal. A delay buffer delays the unattenuated input signal values. Finally, in the embodiment described here, the smoothed attenuation factor values are synchronized with and applied to the delayed input signal values and the resulting attenuated signal is transmitted to an output node and ultimately to one or more acoustic transducers.

US Patent:

7242783, Jul 10, 2007

Filed:

Jan 25, 2006

Appl. No.:

11/340239

Inventors:

William A. Weeks - Santa Cruz CA, US
William R. Morrell - Santa Cruz CA, US

Assignee:

Plantronics, Inc. - Santa Cruz CA

International Classification:

H03G 5/00
H03G 3/00
G10L 19/14

US Classification:

381 98, 381107, 381 99, 381104, 704224, 704225

Abstract:

An audio limiting circuit capable of satisfying frequency dependent limits and time domain constraints, is disclosed. In one illustrative embodiment, an input node receives an unattenuated input signal and a system modeling filter predicts the amount, if any, by which the sound pressure level that would be generated by an acoustic transducer in response to the unattenuated input signal, would exceed one or more predetermined limits. In that embodiment, an energy detector separates the excess predicted sound pressure level into one or more frequency bands and calculates the average acoustic energy associated with each band. A gain logic block determines an attenuation factor based on whether one or more of the predetermined limits has been exceeded and the attenuation factor values are smoothed to minimize abrupt changes to the unattenuated input signal. A delay buffer delays the unattenuated input signal values. Finally, in the embodiment described here, the smoothed attenuation factor values are synchronized with and applied to the delayed input signal values and the resulting attenuated signal is transmitted to an output node and ultimately to one or more acoustic transducers.

US Patent:

20060147049, Jul 6, 2006

Filed:

Dec 30, 2004

Appl. No.:

11/027064

Inventors:

Antony Bayley - Wooton Bassett, GB
William Morrell - Santa Cruz CA, US
Iain McNeill - Aptos CA, US
Kwangsee Woo - Scotts Valley CA, US

Assignee:

Plantronics, Inc. - Santa Cruz CA

International Classification:

H04R 29/00
H03G 3/20
H03G 9/00

US Classification:

381056000, 381057000, 381102000

Abstract:

Sound pressure level limiter with anti-startle feature for audio systems are disclosed. The anti-startle feature may be implemented with a delta incident detector for detecting delta acoustic incidents that exceed a predetermined acoustic startle boundary, a delta limiter for determining an anti-startle gain, and an amplifier to apply the anti-startle gain to the input signal. The delta incident detector may detect delta incidents based on an estimated true SPL delivered by a transducer to a predetermined datum point. The estimated true SPL may be determined by based on a measured receiving frequency response of the transducer. An SPL limiter may also determine an SPL gain in response to detecting an SPL acoustic incident that exceeds a predetermined SPL threshold, and an amplifier may apply the SPL gain to the input signal to reduce it below the threshold.