METHOD OF APPLYING A COMBINED OR HYBRID SOUND-FIELD CONTROL STRATEGY

• US 20150043736A1
• Filed: 03/14/2013
• Published: 02/12/2015
• Est. Priority Date: 03/14/2012
• Status: Active Grant

• Current Assignee: Bang & Olufsen A/S
• Original Assignee: Bang & Olufsen A/S
• Inventors: Olsen, Martin, Mller, Martin Bo
• Granted Patent: US 9,392,390 B2
• Time in Patent Office: Days
• US Class Current: 381/17
• CPC Class Codes: H04S 2400/11 Positioning of individual sound objects, e.g. moving airplane, within a sound field H04S2420/13 takes precedence
• CPC Class Codes: H04S 2420/11 Application of ambisonics in stereophonic audio systems
• CPC Class Codes: H04S 2420/13 Application of wave-field synthesis in stereophonic audio systems
• CPC Class Codes: H04S 7/30 Control circuits for electronic adaptation of the sound field

Abstract

A method of applying a combined control strategy for the reproduction of multichannel audio signals in two or more sound zones, the method comprising deriving a first cost function for controlling the acoustic potential energy, such as on the basis of the Acoustic Contrast Control method and/or the Energy Difference Maximation method, in the zones to obtain acoustic separation between the zones in terms of sound pressure, deriving a second cost function, such as the Pressure Matching method, controlling the phase of the sound provided in the zones, and where a weight is obtained for determining a combination of the first and second cost functions in a combined optimization.

Claims

1. A method of applying a combined control strategy for the reproduction of multichannel audio signals in two or more sound zones, the method comprising:

deriving a first cost function for controlling the acoustic potential energy in the zones to obtain acoustic separation between the zones in terms of sound pressure,

deriving a second cost function controlling the phase of the sound provided in the zones,

where a weight is obtained for determining a combination of the first and second cost functions in a combined optimization.

2. A method according to claim 1, wherein the first cost function is a cost function of the Acoustic Contrast Control method.

3. A method according to claim 1 or 2, wherein the first cost function is a cost function of the Energy Difference Maximation method.

4. A method according to any of the preceding claims, wherein the second cost function is a cost function of the Pressure Matching method.

5. A method according to any of the preceding claims, wherein the step of deriving the first cost function comprises deriving a cost function where the acoustic potential energy in each zone being proportional to the mean square sound pressure in a zone as:

E_pot∝

∫

_S2|p(x)|²da(x)

6. A method according to any of the preceding claims, wherein the step of deriving the second cost function comprises evaluating the phase control using the resulting reproduction error and to obtain a low reproduction error, the reproduction error being defined as:

7. A method according claim 6, where the reproduction error is controlled in points sampling the bright zone.

8. A method according claim 7, where method is combining the cost functions from Pressure Matching (10) and Energy Difference Maximization (6) into a single one including a weight for controlling the tradeoff between the methods in the combined optimization.

9. A method according claim 8, where the cost functions is an unconstrained optimization given as:

f₍q)=q^H(ζ

R_D−

R_B)q+α

(Gq−

p^d)^H(Gq−

p^d),  

 

(12)

10. A method according claim 8, where the source weights are calculated from the stationary points where the gradient is zero, and where the stationary points are determined as given:

(ζ

R_D−

R_B+α

G^HG) q=α

G^Hp^d.  

 

(13)

11. A method according to any of the preceding claims, further comprising the steps of

deriving from the combined optimization, parameters for driving each of a plurality of loudspeakers,

driving the loudspeakers in accordance with the derived parameters.

12. A method according to any of the preceding claims, wherein the step of determining the weight comprises deriving the second cost function so as to have a predetermined maximum reproduction error from a plane wave in a predetermined one of the zones.

13. A method according to claim 12, wherein the maximum reproduction error is 15%.