Real-time loudspeaker distance estimation with stereo audio

Patent metadata

Field	Value
Publication number	US-2016249153-A1
Application number	US-201615050609-A
Country	US
Kind code	A1
Filing date	Feb 23, 2016
Priority date	Feb 24, 2015
Publication date	Aug 25, 2016
Grant date	—

Abstract

A method for estimating a distance between a first and a second loudspeaker characterized by playing back a first stereo source signal vector s 1 on the first loudspeaker, and playing back a second stereo source signal vector s 2 on the second loudspeaker, acquiring a first recorded signal vector x 1 , using a first microphone arranged adjacent to the first loudspeaker, and acquiring a second recorded signal vector x 2 from a second microphone arranged adjacent to the second loudspeaker, wherein x 1 and x 2 are N-dimensional vectors, setting the distance equal to ηv/f, where v is the speed of sound, f is the sampling frequency, and η is an estimated sample delay of a source signal played back on one of the loudspeakers and a recording acquired by a microphone at the other loudspeaker.

First claim

what is claimed is:

1 . A method for estimating a distance between a first and a second loudspeaker characterized by:
(a) playing back a first stereo source signal vector s 1 on the first loudspeaker, and playing back a second stereo source signal vector s 2 on the second loudspeaker; (b) acquiring a first recorded signal vector x 1 , using a first microphone arranged adjacent to the first loudspeaker, and acquiring a second recorded signal vector x 2 from a second microphone arranged adjacent to the second loudspeaker, wherein x 1 and x 2 are N-dimensional vectors; (c) setting the distance equal to ηv/f, where v is the speed of sound, f is the sampling frequency, and η is an estimated sample delay of a source signal played back on one of the loudspeakers and a recording acquired by a microphone at the other loudspeaker, (d) where the delay η is estimated by

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.

where:

s i (η) =ZA i d (η)
is the source signal vector to loudspeaker i shifted by i samples, where
z (ω)=[1 exp( j ω) . . . exp( j ω( N− 1))] T

Z=[z (−2π L/N ) . . . 1 . . . z (2π L/N )]

d (η)=[exp( j 2πη L/N ) . . . 1 . . . exp(− j 2 πηL/N )] T

A i =N −1 diag( Z H s i (0))
N is the number of elements in the vector S i (η), and L=N/2 if N is even and L=(N−1)/2 if N is odd;
where:
C i =γσ 2 [Z ( A 1 A 1 H +A 2 A 2 H ) Z H +γ −1 I N ].

is a covariance matrix modeling both reverberation and measurement noise, where σ 2 is an unknown variance of the measurement noise and γ is a scaling factor; and
where:
R i =I N −B i ( B i H C i −1 B i ) −1 B i H C i −1

is a matrix filtering out the loudspeakers own signal in the microphone recordings, where
B i =ZA i F
F=[d (0) d (1) . . . d ( M− 1)]
and M is a user-defined length of the filter.

2 . The method according t

Assignees

• Bang & Olufsen As

Inventors

• Nielsen Jesper Kjaer

Classifications

• H04S7/305

  Electronic adaptation of stereophonic audio signals to reverberation of the listening space (H04S7/301 takes precedence) · CPC title

• H04R5/02

  Spatial or constructional arrangements of loudspeakers · CPC title

• H04R2205/024

  Positioning of loudspeaker enclosures for spatial sound reproduction · CPC title

• H04S7/301 Primary

  Automatic calibration of stereophonic sound system, e.g. with test microphone · CPC title