Method, system and apparatus for loudspeaker excursion domain processing

Patent metadata

Field	Value
Publication number	US-2016157014-A1
Application number	US-201414555632-A
Country	US
Kind code	A1
Filing date	Nov 27, 2014
Priority date	Nov 27, 2014
Publication date	Jun 2, 2016
Grant date	—

Abstract

A method, system and apparatus for loudspeaker excursion domain processing are provided. At a device comprising: a processor, a loudspeaker comprising a voice coil, one or more devices for determining loudspeaker voltage and current as a function of time, t, and a memory storing a Bl product for the loudspeaker, loudspeaker currents I(t) and corresponding voltages V(t) are received at the processor from the one or more devices. A current-from-voltage transfer function H IV (ω) is derived from the loudspeaker currents I(t) and voltages V(t), as a function of frequency, ω. A Fourier space excursion-from-voltage transfer function H XV (ω) is determined, whos e form is constrained by parameters H IV (ω), Bl, R vc , and L vc , where: R vc comprises a resistance of the voice coil; and L vc comprises an inductance of the voice coil. Filter coefficients are determined using H XV (ω), which are used in a filter applied to an input signal for the loudspeaker.

First claim

What is claimed is:

1 . A device comprising:
a processor, a loudspeaker comprising a voice coil, one or more devices configured to determine loudspeaker voltage and loudspeaker current, and a memory storing a Bl product for the loudspeaker, the processor configured to:
receive a plurality of loudspeaker currents I(t) and a corresponding plurality of loudspeaker voltages V(t) from the one or more devices as a function of time, t;
derive a current-from-voltage transfer function H IV (ω) from the plurality of loudspeaker currents I(t) and the corresponding plurality of loudspeaker voltages V(t), as a function of frequency, ω;
determine a Fourier space excursion-from-voltage transfer function H XV (ω), whose form is constrained by parameters H IV (ω), Bl, R vc , and L vc , where: R vc comprises a resistance of the voice coil; and L vc comprises an inductance of the voice coil;
determine filter coefficients using the Fourier space excursion-from-voltage transfer function, H XV (ω); and,
apply a filter to an input signal for the loudspeaker using the filter coefficients.

2 . The device of claim 1 , wherein the Fourier space excursion-from-voltage transfer function H XV (ω) is determined using:

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where: j denotes a square root of −1.

3 . The device of claim 1 , wherein the processor is further configured to determine the resistance, R vc , of the voice coil from one or more of: a value of the resistance, R vc , stored in the memory; determining the resistance, R vc , by adding a tone to the input signal at a frequency where impedance of the voice coil is about a DC (direct current) electrical resistance of the voice coil; and filtering the tone out of a voltage sense signal and a current sense signal and taking the quotient.

4 . The device of claim 1 , wherein the processor is further configured to determine the inductance, L vc , of the voice coil from one or more of: value of the inductance, L vc , stored in the memory; determining the inductance, L vc , by adding a tone to the input signal at a frequency where impedance of the voice coil is about a sum of electrical impedance of voice coil inductance and voice coil resistance; and filtering the tone out of a voltage sense signal and a current sense signal the deriving the inductance, L vc , using a given value of the resistance, R vc .

5 . The device of claim 1 , wherein the processor is further configured to determine the Fourier space excursion-from-voltage transfer function H XV (ω) one or more of continuously and periodically, and update the filter accordingly.

6 . The device of claim 1 , wherein the processor is further configured to place limits on a filtered input signal, the limits based on a maximum excursion of the voice coil, the limits placed on the filter in an excursion domain.

7 . The device of claim 1 , wherein the processor is further configured to:
determine an inverse of the Fourier space excursion-from-voltage transfer function, H XV (ω); determine inverse filter coefficients using the inverse of the Fourier space excursion-from-voltage transfer function, H XV (ω); and, convert a filtered input signal to an output signal using a voltage-from-excursion transfer function filter, derived from the inverse filter coefficients, to drive the voice coil.

8 . The device of claim 1 , wherein the processor is further configured to:
derive a scaling factor for a portion of the input signal from a ratio of a pre-filter excursion of the input signal prior to applying the filter, and a post-filter excursion after applying the filter; and, apply the scaling factor to the portion of the input signal to produce a portion of an output signal driving the voice coil.

9 . The device of claim 8 , wherein the portion of the input signal comprises a given time period of the input signal, and the processor is further configured to derive respective scaling factors for each of a plurality of given time periods and apply the respective scaling factors to the input signal for each of the plurality of the given time periods.

10 . The device of claim 1 , wherein the processor is further configured to apply an equalization filter to a filtered input signal, prior to placing limits on the filtered input signal, by one or more of: flattening the fi

Assignees

• Blackberry Ltd

Inventors

• Van Schyndel Andre John
• Gordy James David
• Laska Brady Nicholas

Classifications

• H04R2499/11

  Transducers incorporated or for use in hand-held devices, e.g. mobile phones, PDA's, camera's · CPC title

• H04R3/007 Primary

  Protection circuits for transducers · CPC title

• H04R29/003

  of the moving-coil type · CPC title