Method, system and apparatus for loudspeaker excursion domain processing

Patent metadata

Field	Value
Publication number	US-2016157015-A1
Application number	US-201414555635-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 and thermal limiting are provided. At a device comprising: a processor; a loudspeaker and voice coil, device(s) for determining loudspeaker voltage and current; a volume device; and a memory storing a Bl product for the loudspeaker, a Fourier space excursion-from-voltage transfer function H XV (ω) is determined. An acoustic response of the loudspeaker below a dovetail frequency, is determined, relative to a respective acoustic response at the dovetail frequency, using at least a second time derivative of the transfer function H XV (ω). An equalization is determined using the acoustic response, comprising gains that, when applied to the acoustic response, will adjust the acoustic response to the respective acoustic response at the respective acoustic response at the dovetail frequency. Filter coefficients are determined corresponding to the equalization, which are used in a filter applied to a loudspeaker input signal.

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; a volume device configured to set a volume of the loudspeaker; and a memory storing a Bl product for the loudspeaker, the processor configured to: determine a Fourier space excursion-from-voltage transfer function H XV (ω); determine an acoustic response of the loudspeaker, as a function of frequency, below a dovetail frequency, and relative to a respective acoustic response at the dovetail frequency, using at least a second time derivative of the Fourier space excursion-from-voltage transfer function H XV (ω); determine an equalization as a function of frequency using the acoustic response, the equalization comprising gains that, when applied to the acoustic response, will adjust the acoustic response to the respective acoustic response at the respective acoustic response at the dovetail frequency; determine filter coefficients of a filter that corresponds to the equalization; and, apply the filter to an input signal for the loudspeaker.

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

H
XV



(
ω
)

=

1
Bl



[

1
-

H
IV



(
ω
)



R
vc

jω

-

L
vc



H
IV



(
ω
)

]

where: j denotes a square root of −1; R vc comprises a resistance of the voice coil; L vc comprises an inductance of the voice coil; and, H IV (ω) comprises a current-from-voltage transfer function derived from a plurality of loudspeaker currents I(t) and a corresponding plurality of loudspeaker voltages V(t) measured by the one or more devices.

3 . The device of claim 1 , wherein the processor is further configured to: determine available excursion of the voice coil at frequencies below the dovetail frequency, at a volume setting of the volume device, the available excursion comprising a difference between respective excursions at respective frequencies, as determined from the acoustic response, and an excursion limit of the voice coil, and wherein determining the equalization as a function of the frequency comprises using the available excursion.

4 . The device of claim 1 , wherein the processor is further configured to determine the acoustic response of the loudspeaker by determining an absolute acoustic response expressed with respect to pressure, p, and assuming that the loudspeaker comprises a sealed back cavity, using:

p
=

ρ




S
d

4



π



r



x
¨

where r is the distance from the loudspeaker, ρ is the density of a medium surrounding the voice coil, S d is an area of a diaphragm of the loudspeaker, {umlaut over (χ)} is the second time derivative of the excursion-from-voltage transfer function, H XV (ω).

5 . The device of claim 1 , wherein the processor is further configured to: determine a minimum frequency for which the equalization can be applied to the acoustic response without exceeding the excursion limit; and, determine at least the equalization between the minimum frequency and the dovetail frequency.

6 . The device of claim 1 , wherein the dovetail frequency comprises a maximum frequency above which the excursion of the voice coil is one or more of below a minimum excursion and the excursion is not significantly affected.

7 . The device of claim 1 , wherein the processor is further configured to apply limits using one or more of a maximum applied gain and a minimum equalization frequency.

8 . The device of claim 1 , wherein the processor is further configured to adjust the gains to match a respective excursion of at least one other loudspeaker.

9 . The device of claim 1 , wherein the loudspeaker comprises a first loudspeaker of a pair of two stereo loudspeakers, and the processor is further configured to adjust the gains to match a respective excursion of at least a second loudspeaker of the pair of two stereo loudspeakers.

10 . The device of claim 1 , wherein the processor is further configured to control the loudspeaker to emit a sound at a given absolute acoustic level in a calibration procedure.

11 . A method comprising:
determining, at a processor of a device, a Fourier space excursion-from-voltage transfer function H XV (ω), the device comprising: the processor, a loudspeaker comprising a voice coil, one or more devices configured to determine loudspeaker voltage and loudspeaker current; a volume device configured to set a volume of the loudspeaker; and a memory storing a Bl product for the loudspeaker; determining, at the processor, an acoustic response of the loudspeaker, as a function of frequency, below a dovetail frequency, and relative to a respective acoustic response at the dovetail frequency, using at least a second time derivative of the Fourier space excursion-from-voltage transfer function H XV (ω); determining, at the processor, an equalization as a function of frequency using the acoustic response, the equalization comprising gains that, when applied to the acoustic response, wil

Assignees

• Blackberry Ltd

Inventors

• Van Schyndel Andre John

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