Loudspeaker position estimation

• US 8,279,709 B2
• Filed: 11/05/2007
• Issued: 10/02/2012
• Est. Priority Date: 07/18/2007
• Status: Active Grant

• Current Assignee: BAG & Olufsen A/S, Bang & Olufsen a/s
• Original Assignee: Bang & Olufsen a/s
• Inventors: Choisel, Sylvain, Martin, Geoffrey Glen, Hlatky, Michael
• Primary Examiner(s): Alsomiri, Isam
• Assistant Examiner(s): HULKA, JAMES R
• Application Number:
  US12/669,080
• Publication Number:
  US 20100195444A1
• Time in Patent Office: 1,793 Days
• Field of Search: 367/127, 367/129
• US Class Current: 367/127
• CPC Class Codes: H04R 2205/024 Positioning of loudspeaker enclosures for spatial sound reproduction
• CPC Class Codes: H04R 2400/01 Transducers used as a loudspeaker to generate sound aswell as a microphone to detect sound
• CPC Class Codes: H04R 5/02 Spatial or constructional arrangements of loudspeakers
• CPC Class Codes: H04S 7/301 Automatic calibration of stereophonic sound system, e.g. with test microphone

Abstract

The invention relates to an automated estimation of the position (co-ordinates) of a set of loudspeakers in a ioom Based on measured impulse responses the distances between each pair of loudspeakers are estimated, thereby forming a distance matrix, and the resultant distance matrix is used by a multidimensional scaling (MDS) algorithm to estimate the co-ordinates of each individual loudspeaker An improved co-ordinate estimation can, if desired, be derived by utilizing the stress values provided by the MDS algorithm.

Claims

1. A method for estimating a position of N sound-emitting transducers, where N≧

2, where the method comprises the following steps;

a) determining individual distances d_ij, or quantities uniquely defining these distances, between any given sound-emitting transducer (T_i) and each of the remaining sound-emitting transducers (T_j);

b) based on said individual distances d_ij between any given sound-emitting transducer (T_i) and each of the remaining sound-emitting transducers (T_j), i.e. based on a distance matrix M comprising the individual determined distances d_ij or based on said other determined quantities, estimating relative co-ordinates (x_i′

, y_i′

, z_i′

) of each of said sound-emitting transducers (T₁, T₂, . . . T_N) by a multidimensional scaling (MDS) technique or algorithm;

c) executing an error identification and correction when an overall stress value provided by said MDS algorithm exceeds a given maximum value, said executing step including the steps of subdividing said distance matrix M into sub-matrixes, thereby providing stress values for each of these sub-matrixes, and determining that the or those sub-matrixes resulting in stress values outside a given tolerance region comprise at least one pair of transducers, the determined distance between which is erroneous;

d) providing the co-ordinates of the pair of said at least one pair of transducers to an error detection algorithm thereby providing an error matrix;

e) providing said error matrix and said overall stress value to an optimization algorithm that optimizes said distance matrix;

f) based on the optimized distance matrix, estimating the relative co-ordinates (x_i′

, y_i′

, z_i′

) of each of said sound-emitting transducers (T₁, T₂, . . . T_N) by the multidimensional scaling (MDS) technique or algorithm thereby obtaining an updated stress value;

g) comparing said updated stress value with said given tolerance region of stress values and repeating steps (c) through (f) until said updated stress value is outside said tolerance; and

h) when the updated stress value is outside said tolerance region, providing the relative co-ordinates that are based on the optimized distance matrix as the result of the preceding steps.

2. A method according to claim 1 for estimating the position of N sound-emitting transducers, where N≧

2, the method further comprising the following steps;

for each pair (i, j) of sound-emitting transducers (T₁, T₂, . . . T_N) determining an impulse response IR_ij(t) by emitting an acoustic signal from one of said transducers of a given pair (i, j) of transducers and recording a resultant acoustic signal at the other transducer of the given pair (i, j) of transducers, thereby attaining a set of impulse responses IR_ij(t) for each of said pairs of sound-emitting transducers;

based on said determined set of impulse responses IR_ij(t), determining propagation times t_ij for sound propagation from any given sound-emitting transducer (T_i) to any other given sound-emitting transducer (T_j);

based on said propagation times t_ij, determining individual distances d_ij between any given sound-emitting transducer (T_i) and the remaining sound-emitting transducers (T_j) by multiplication of each of said propagation times t_ij by c, where c is the propagation speed of sound, whereby a distance matrix M is provided;

based on said individual distances d_ij between any given sound-emitting transducer (T_i) and the remaining sound-emitting transducers (T_i) or on said distance matrix M, estimating the relative co-ordinates (x_i′

, y_i′

, z_i′

) of each of said sound-emitting transducers (T₁, T₂, . . . T_N) by the multidimensional scaling (MDS) technique or algorithm.

3. A method according to claim 2, wherein the acoustic signal emitted from a given transducer is recorded at one of the N-1 remaining transducers at a time.

4. A method according to claim 2, wherein the acoustic signal emitted from a given transducer is recorded at all of the remaining N-1 transducers simultaneously.

5. A method according to claim 2, where said impulse responses IR_ij(t) are determined using maximum length sequence (MLS) measurements.

6. A method according to claim 2, where said recording of the emitted measurement signal is attained by a microphone provided as an integral part of each of said sound-emitting transducers.

7. A method according to claim 2, where said recording of the emitted measurement signal is attained by each of said sound-emitting transducers themselves, each transducer being able to function both as a sound-emitting transducer and as a sound-recording transducer.

8. A method according to claim 2, where said propagation times t_ij are determined on the basis of said impulse responses IR_ij(t) by determining the maximum value or the minimum value of the impulse response and determining the sample where the impulse response reaches a value that is V % of said maximum or minimum value.

9. A method according to claim 8, where V is 10%.

10. A method according to claim 1, where stress values provided by the MDS algorithm are used to improve co-ordinate estimation.

11. A method according to claim 1, where said erroneously determined distances or said other erroneously determined other quantities uniquely defining these distances are corrected by an iterative optimisation algorithm.

12. A method according to claim 1, where room-related co-ordinates (x, y, z), relating to a specific room in which the sound-emitting transducers are positioned, are obtained from said relative co-ordinates (x_i′

, y_i′

, z_i′

) by a linear transformation of the relative co-ordinates (x_i′

, y_i′

, z_i′

).

13. A system for estimating a position of N sound-emitting transducers, where N≧

2, where the system comprises;

a generator which provides a given one of said sound-emitting transducers with a test signal that causes said given transducer to emit an acoustic test signal that can be picked up by each of the remaining said transducers;

a receptor in each of the transducers for picking up said acoustic test signal at each separate receiving said transducer;

an analyzer which determines individual propagation times t_ij between each said given emitting transducer T_i and each said receiving transducer T_j based on said test signal provided to said emitting transducer T_i and on said signal picked up by said receiving transducer T_j;

a distance calculator which calculates a distance between said first and second locations in space by multiplication of corresponding ones of said propagation times t_ij with the propagation speed c of sound;

a multidimensional scaling (MDS) estimator which estimates, based on the determined distance between respective ones of said sound-emitting transducers, a set of relative co-ordinates (x_i′

, y_i′

, z_i′

) for each of the N individual sound-emitting transducers;

an error identification and correction mechanism, forming part of an iterative optimisation loop together with a position detection part,

which subdivides a matrix M comprising the individual determined distances d_ij into sub-matrixes,

which applies the MDS algorithm on each of said sub-matrixes,

which thereby provides stress values for each of these sub-matrixes,

which determines that the or those sub-matrix(es) resulting in stress value(s) outside a given tolerance region comprise at least one pair of transducers, the determined distance between which is erroneous,

which provides the co-ordinates of the pair of said at least one pair of transducers to an error detection algorithm thereby producing an error matrix;

which provides said error matrix and said overall stress value to an optimization algorithm that optimizes said distance matrix;

which, based on the optimized distance matrix, estimates the relative co-ordinates (x_i′

,y_i′

, z_i′

) of each of said sound-emitting transducers (T₁, T₂, . . . T_N) by the multidimensional scaling (MDS) technique or algorithm thereby obtaining an updated stress value;

which compares said updated stress value with said given tolerance region of stress values and which utilizes the iterative optimization loop until said updated stress value is outside said tolerance; and

when the updated stress value is outside said tolerance region, which provides the relative co-ordinates that are based on the optimized distance matrix.

14. A system according to claim 13, where the system furthermore comprises a linear transformer which provides room-related co-ordinates (x, y, z), relating to a specific room in which the sound-emitting transducers are positioned, obtained from said relative co-ordinates (x_i′

, y_i′

, z_i′

) by a linear transformation of the relative co-ordinates (x_i′

, y_i′

, z_i′

).

15. A system according to claim 13, where said generator, analyzer, calculator, and multidimensional scaling (MDS) estimator are integrated as a common position estimating processor.

16. A system according to claim 15, where said common position estimating processor is provided as an integral part of one of said sound-emitting transducers.

17. A system according to claim 13, where sound reception at a second location in space is carried out by a microphone at said second location in space.

18. A system according to claim 13, where sound reception at a second location in space is carried out by a sound-emitting transducer at said second location in space, where said sound-emitting transducer can also function as a sound-recorder.

19. A system according to claim 13, further comprising a storage which stores said set of measured impulse responses IR_ij(t) and/or said distance matrix M and/or said relative co-ordinates (x_i′

, y_i′

, z_i′

) and/or said room-related co-ordinates (x, y, z).