Speaker output characteristic correction system and sound system

Patent metadata

Field	Value
Publication number	US-12501215-B2
Application number	US-202318376643-A
Country	US
Kind code	B2
Filing date	Oct 4, 2023
Priority date	Oct 19, 2022
Publication date	Dec 16, 2025
Grant date	Dec 16, 2025

Abstract

A controller calculates individual parameters, including nonlinear parameters of a speaker model, based on a measured displacement of a vibration system of a speaker. A sound generator outputs an audio signal, and an output flattening filter adjusts gains of individual bands of an audio signal so that a frequency characteristic of a volume of sound output by the speaker is flattened in accordance with a speaker model obtained by linearizing calculated parameters and outputs a resultant audio signal. A nonlinear inverse filter corrects the resultant audio signal by signal processing adapted to the gains of the output flattening filter so that the nonlinear distortion of the speaker is suppressed in accordance with the speaker model including the nonlinear parameters and outputs the corrected audio signal as an output audio signal to the speaker via an amplifier.

First claim

The invention claimed is:

1 . A speaker output characteristic correction system that corrects an output characteristic of a speaker for an audio signal output from a sound generator, the speaker output characteristic correction system comprising:
an output flattening filter configured to receive an audio signal output from the sound generator as an input first audio signal and to output a second audio signal; a nonlinear inverse filter configured to receive the second audio signal as an input and to output a signal to the speaker:
wherein a filter characteristic for adjusting gains of individual bands of the first audio signal so that a frequency characteristic of a volume of sound output by the speaker relative to the first audio signal is flattened is set to the output flattening filter as a filter characteristic of the output flattening filter, and
wherein an inverse characteristic of a nonlinear characteristic of the speaker is set to the nonlinear inverse filter as a filter characteristic of the nonlinear inverse filter;
a displacement measurement section configured to measure a displacement of a vibration system of the speaker; a speaker model calculator configured to calculate a speaker model of the speaker having a plurality of parameters including nonlinear parameters based on the displacement measured by the displacement measurement section in a state in which a predetermined audio signal is output to the speaker; and a filter characteristic setter configured to calculate a linear approximation speaker model that is a speaker model in which the individual parameters of the calculated speaker model are linearized, to calculate a filter characteristic in which a frequency characteristic of a volume of sound output by the speaker is flattened in accordance with the calculated linear approximation speaker model, and to set the calculated filter characteristic to the output flattening filter as a filter characteristic of the output flattening filter; wherein the filter characteristic setter is configured to set, as the filter characteristic of the linear inverse filter, a filter characteristic that matches an inverse characteristic of a nonlinear characteristic of the speaker model indicated by the parameters of the speaker model calculated by the speaker model calculator.

2 . The speaker output characteristic correction system according to claim 1 , further comprising:
a displacement measurement section configured to measure a displacement of a vibration system of the speaker; a speaker model calculator configured to calculate a speaker model of the speaker having a plurality of parameters including nonlinear parameters based on the displacement measured by the displacement measurement section in a state in which a predetermined audio signal is output to the speaker; and a filter characteristic setter configured to set, as the filter characteristic of the linear inverse filter, a filter characteristic that matches an inverse characteristic of a nonlinear characteristic of the speaker model indicated by the parameters of the speaker model calculated by the speaker model calculator.

3 . A sound system including the speaker output characteristic correction system according to claim 1 , the speaker, and the sound generator.

4 . A speaker output characteristic correction system that corrects an output characteristic of a speaker for an audio signal output from a sound generator, the speaker output characteristic correction system comprising:
an output flattening filter configured to receive an audio signal output from the sound generator as an input first audio signal and to output a second audio signal; a nonlinear inverse filter configured to receive the second audio signal as an input and to output a signal to the speaker:
wherein a filter characteristic for adjusting gains of individual bands of the first audio signal so that a frequency characteristic of a volume of sound output by the speaker relative to the first audio signal is flattened is set to the output flattening filter as a filter characteristic of the output flattening filter, and
wherein an inverse characteristic of a nonlinear characteristic of the speaker is set to the nonlinear inverse filter as a filter characteristic of the nonlinear inverse filter;
a displacement measurement section configured to measure a displacement of a vibration system of the speaker; a speaker model calculator configured to calculate a speaker model of the speaker having a plurality of parameters including nonlinear parameters based on the displacement measured by the displacement measurement section in a state in which a predetermined audio signal is output to the speaker; and a filter characteristic setter configured to calculate a linear approximation speaker model that is a speaker model in which the individual parameters of the calculated speaker model are linearized, to calculate a filter characteristic in which a frequency characteristic of a volume of sound output by the speaker is flattened in accordance with the calculated linear approximation speaker model, and to set the calculated filter characteristic to the output flattening filter as a filter characteristic of the output flattening filter; wherein the output flattening filter includes:
a band divider configured to divide the first audio signal into a plurality of per-band signals, which are signals for individual bands of the first audio signal;
gain calculators corresponding to the individual bands, which are configured to calculate gains of the bands;
gain adjusters corresponding to the individual bands, which are configured to provide the gains of the individual bands calculated by the gain calculators to the per-band signals of the bands; and
a mixer configured to mix the per-band signals having gains adjusted by the gain adjusters and to output resultants as the second audio signal;
each of the gain calculators corresponding to the individual bands includes:
a linear approximation speaker model configured to receive a corresponding one of the per-band signals of the bands as an input;
a flattening speaker model configured to receive a corresponding one of the per-band signals of the bands as an input; and
a gain output section configured to output a value obtained by dividing an effective value of an output of the flattening speaker model by an effective value of an output of the linear approximation speaker model as a gain of the corresponding one of the bands; and
the filter characteristic setter is configured to:
calculate, based on the calculated linear approximation speaker model, a speaker model in which a frequency characteristic of a volume of sound output by the speaker is flatter than the linear approximation speaker model as the flattening speaker model; and
set a filter characteristic of the output flattening filter by setting the calculated linear approximation speaker model and the calculated flattening speaker model in the gain calculators corresponding to the individual bands.

5 . The speaker output characteristic correction system according to claim 4 , wherein:
the filter characteristic setter is configured to calculate a speaker model in which the parameters of the linear approximation speaker model are changed so that a resonance frequency moves to a lower frequency side relative to a resonance frequency of the linear approximation speaker model as the flattening speaker model.

6 . The speaker output characteristic correction system according to claim 5 , wherein
the filter characteristic setter is configured to set, as the filter characteristic of the linear inverse filter, a filter characteristic that matches an inverse characteristic of a nonlinear characteristic of the speaker model indicated by the parameters

Assignees

• Alps Alpine Co Ltd

Inventors

• Saito Yuji

Classifications

• H04R2430/03

  Synergistic effects of band splitting and sub-band processing · CPC title

• H04R2430/01

  Aspects of volume control, not necessarily automatic, in sound systems · CPC title

• H04R29/001 Primary

  for loudspeakers (H04R29/007 takes precedence) · CPC title

• H04R3/002

  Damping circuit arrangements for transducers, e.g. motional feedback circuits · CPC title

• H04R3/04 Primary

  for correcting frequency response · CPC title