Adaptive audio systems and sound reproduction systems

• US 5,949,894 A
• Filed: 03/18/1997
• Issued: 09/07/1999
• Est. Priority Date: 03/18/1997
• Status: Expired due to Fees

• Current Assignee: Adaptive Audio Limited
• Original Assignee: Adaptive Audio Limited
• Inventors: Orduna-Bustamante, Felipe, Hamada, Hareo, Nelson, Philip Arthur
• Primary Examiner(s): Kuntz, Curtis A.
• Assistant Examiner(s): NGUYEN, DUC MINH
• Application Number:
  US08/820,518
• Time in Patent Office: 903 Days
• Field of Search: 381/1, 381/17-19, 381/24-26, 381/86, 381/300, 381/309, 381/310-311, 364/724.12, 364/724.16, 364/724.17, 364/724.19, 364/724.2
• US Class Current: 381/300
• CPC Class Codes: H04S 1/002 Non-adaptive circuits, e.g. manually adjustable or static, for enhancing the sound image or the spatial distribution control circuits for electronic adaptation of the sound field H04S7/30
• CPC Class Codes: H04S 7/301 Automatic calibration of stereophonic sound system, e.g. with test microphone
• CPC Class Codes: H04S 7/307 Frequency adjustment, e.g. tone control H04S7/301 takes precedence

Abstract

A sound reproduction system comprises a plurality of loudspeakers (S1, S2) spaced from a listener at a location (M1, M2), and a loudspeaker drive means (H) for driving the loudspeakers (S1, S2) in response to a plurality of channels of a sound recording (x) of the type being suitable for playing normally through a plurality of reference speakers that are optimally positioned at locations that are displaced from the actual positions of the loudspeakers (S1, S2). The loudspeaker drive includes a filter (H), having a filter characteristic selected by minimising the difference between a desired sound field that would be created by playing the unfiltered sound recording (x) through the reference speakers and sound field reproduced at the listener location (M1, M2) by playing the recording through the speakers (S1, S2). This results in creating a local sound field at the listener location (M1, M2) which is substantially equivalent to the local field that would result from playing the unfiltered sound recording (x) through the reference speakers.

Claims

1. A sound reproduction system comprising:

a plurality of loudspeakers (S1, S2) spaced from a listener at a location (M1, M2);

loudspeaker drive means (H) for driving the loudspeakers (S1, S2) in response to a plurality of channels of a sound recording (x) of the type being suitable for playing normally through a plurality of reference speakers that are optimally positioned at locations that are displaced from the actual positions of the loudspeakers (S1, S2), wherein the loudspeaker drive means includes a digital filter means (H), having a filter characteristic selected by minimising the difference between a desired sound field that would be created by playing the unfiltered sound recording (x) through the reference speakers and a sound field reproduced at the listener location (M1, M2) by playing the recording through the speakers (S1, S2) in order to create a local sound field at the listener location (M1, M2) which is substantially equivalent to the local field that would result from playing the unfiltered sound recording (x) through the reference speakers, the digital filter means (H) being designed by a filter design process in which the filter coefficients which determine said filter characteristics of the digital filter means (H) are designed so as to approximately reproduce in the sound field the desired signals (d) which are specified by the use of a filter matrix (A) used to relate the desired signals (d) of said desired sound field to recorded signals (x).

2. A sound reproduction system as claimed in claim 1, wherein, in use, the actual positions of the loudspeakers (S1, S2) are predetermined positions that are asymmetric with respect to the listener location (M1, M2).

3. A sound reproduction system as claimed in claim 1, wherein the actual positions of the loudspeakers (S1, S2) are predetermined positions that are more narrowly spaced from each other than the spacing of the reference speakers.

4. A sound reproduction system comprising:

a plurality of loudspeakers (S1, S2) spaced from a listener at a location (M1, M2);

loudspeaker drive means (H) for driving the loudspeakers (S1, S2) in response to a plurality of channels of a sound recording (x) of the type being suitable for playing normally through a plurality of reference speakers that are optimally positioned at locations that are displaced from the actual positions of the loudspeakers (S1, S2), wherein the loudspeaker drive means includes a digital filter means (H), having a filter characteristic selected by minimising the difference between the time history of a desired sound field that would be created by playing the unfiltered sound recording (x) through the reference speakers and the time history of the sound field reproduced at the listener location (M1, M2) by playing the recording through the speakers (S1, S2) in order to create a local sound field at the listener location (M1, M2) which is substantially equivalent to the local field that would result from playing the unfiltered sound recording (x) through the reference speakers, the digital filter means (H) being designed by a filter design process in which the filter coefficients which determine said filter characteristics of the digital filter means (H) are designed so as to approximately reproduce in the sound field the desired signals (d) which are specified by the use of a filter matrix (A) used to relate the desired signals (d) of said desired sound field to recorded signals (x).

5. A sound reproduction system as claimed in claim 4, wherein, in use, the actual positions of the loudspeakers (S1, S2) are predetermined positions that are asymmetric with respect to the listener location (M1, M2).

6. A sound reproduction system as claimed in claim 4, wherein the actual positions of the loudspeakers (S1, S2) are predetermined positions that are more narrowly spaced from each other than the spacing of the reference speakers.

7. A sound reproduction system comprising:

a set of four loudspeakers (S1, S2, S3, S4) which are arranged in use at spaced-apart positions to create a sound field at a first and second predetermined listener locations (M1, M2, M3, M4), within the sound field;

a digital filter means (H) through which the loudspeakers are driven by two channels (x₁, x₂) of a sound recording, the filter means (H) having a filter characteristic selected by minimising an error between a desired sound field that would be created by playing unfiltered channels of the sound recording through a set of reference speakers that are optimally positioned at a location generally symmetric to the first and second predetermined listener locations and a reproduced sound field created by playing the channels of the sound recording through the set of four loudspeakers (S1, S2, S3, S4) in order to create at both the first and second listener locations (M1, M2), (M3, M4) a respective local portion of the sound field which is substantially the same as the sound field portion that would be produced by the reference speakers, the digital filter means (H) being designed by a filter design process in which the filter coefficients which determine said filter characteristics of the digital filter means (H) are designed so as to approximately reproduce in the sound field the desired signals (d) which are specified by the use of a filter matrix (A) used to relate the desired signals (d) of said desired sound field to recorded signals (x).