Room and program responsive loudspeaker system

Patent metadata

Field	Value
Publication number	US-10091583-B2
Application number	US-201414771482-A
Country	US
Kind code	B2
Filing date	Mar 6, 2014
Priority date	Mar 7, 2013
Publication date	Oct 2, 2018
Grant date	Oct 2, 2018

Abstract

A home audio system that includes an audio receiver and one or more loudspeaker arrays is described. The audio receiver measures the acoustic properties of the room in which the loudspeaker arrays reside and the audio characteristics of the sound program content to be played through the loudspeaker arrays. Based on these measurements, the audio receiver assigns a directivity ratio and potentially various beam patterns to one or more segments of the sound program content. The assigned directivity ratio is used by the receiver to play the segment of the sound program content through the loudspeaker arrays. Other embodiments are also described.

First claim

What is claimed is:

1. A method for adjusting sound directional properties of a loudspeaker array, comprising:
measuring, by a processor, acoustic properties of a room containing the loudspeaker array;
determining a first sound directional property for processing to produce a directional pattern from the loudspeaker array according to the measured acoustic properties of the room;
measuring, repeatedly by the processor over the playing time of sound program content to be emitted by the loudspeaker array, audio characteristics of a plurality of audio channels of the sound program content that comprise energy level of a segment of the sound program content, correlation level between two channels in a segment of the sound program content, and detection of speech in a segment of the sound program content;
determining, repeatedly by the processor over the playing time of the sound program content, a second sound directional property for processing to produce a directional pattern from the loudspeaker array according to the measured audio characteristics of the sound program content; and
playing, through the loudspeaker array, the sound program content processed to produce a directional pattern according to the first and second sound directional properties.

2. The method of claim 1 , wherein the first and second sound directional properties each include a ratio of sound directed by the loudspeaker array directly at an intended listener location to the total amount of sound directed by the loudspeaker array into the room.

3. The method of claim 1 , wherein the acoustic properties are measured based on discrete reflections of sound from the loudspeaker array off surfaces and objects in the room.

4. The method of claim 3 , wherein the acoustic properties that are measured based on discrete reflections of sound from the loudspeaker array are used to steer sound output of the array so as to reduce a level of early reflections below a threshold level.

5. The method of claim 2 , wherein the acoustic properties include the reverberation time of the room.

6. The method of claim 5 , wherein the ratio corresponding to the first sound directional property is proportional to the reverberation time of the room.

7. The method of claim 2 , wherein measuring the audio characteristics of the sound program content comprises:
computing a ratio of i) the energy level of a channel of the sound program content and ii) the sum of the energies of all the channels of the sound program content, for each channel.

8. The method of claim 7 , wherein determining the second sound directional property of the sound program content comprises:
increasing the ratio included in the second sound directional property in response to (1) detecting an energy level in a current segment of the sound program content is higher than a predefined energy level or (2) detecting that the computed ratio of the energy level of a channel of the sound program content and the sum of the energies of all the channels of the sound program content, in each channel, is higher than a predefined value;
increasing the ratio included in the second sound directional property in response to detecting that the correlation level between the first and second channels in the current segment of the sound program content is higher than a predefined correlation level; and
adjusting the ratio included in the second sound directional property in response to detecting speech in the current segment of the sound program content.

9. The method of claim 8 , wherein the predefined energy level and the predefined correlation level correspond to the energy and correlation levels in a previous segment of the sound program content that precedes the current segment.

10. The method of claim 2 , wherein non-overlapping frequency divisions of the sound program content are represented by separate ratios included in the second sound directional property, wherein determining the second sound directional property of the sound program content further comprises:
increasing the separate ratios for higher frequency divisions; and
decreasing the separate ratios for lower frequency divisions.

11. The method of claim 7 , wherein the loudspeaker array plays the sound program content from the first and second channels, simultaneously outputting the first and second channels with individual first and second directional properties for each channel.

12. An audio receiver for driving a loudspeaker, comprising:
a room acoustics unit for measuring acoustic properties of a room and determining a first sound directional property for processing to produce a directional pattern from the loudspeaker according to the measured acoustic properties of the room;
a content characteristics unit for measuring audio characteristics of a segment of sound program content and determining a second sound directional property for processing to produce a directional pattern from the loudspeaker according to the measured audio characteristics of the segment of the sound program content wherein the content characteristics unit comprises
an energy level unit for measuring energy level of the segment of the sound program content,
a correlation level unit for measuring a correlation level between first and second source channels in the segment of the sound program content, wherein the segment of the sound program content is a segment about to be played through the loudspeaker, and
a speech detector for detecting speech in the segment of the sound program content, wherein the energy level, the correlation level, and the detection of speech are included in the audio characteristics; and

a driver unit for playing the segment of the sound program content through the loudspeaker processed to produce a directional pattern according to the first and second directional properties.

13. The audio receiver of claim 12 , wherein the room acoustics unit and the content characteristics unit are to determine the first and second sound directional properties as including first and second directional ratios, respectively, which are ratios of sound directed by the loudspeaker at a target in the room to the total amount of sound directed by the loudspeaker into the room.

14. The audio receiver of claim 12 , wherein the room acoustics unit is to determine the first sound directional property as including a first directional ratio which is proportional to the reverberation time of the room.

15. The audio receiver of claim 12 , wherein the room acoustics unit detects early reflections in the room and the driver unit outputs a directional beam to reduce the effect of the early reflections.

16. The audio receiver of claim 15 , wherein the directional beam is steered so as to avoid early reflections above a criteria level.

17. The audio receiver of claim 12 , wherein the room acoustics unit measures the acoustic properties of the room prior to playing the sound program content through the loudspeaker, and
wherein the content characteristics unit measures the audio characteristics of the segment prior to playing the segment through the loudspeaker.

18. An apparatus for sound directionality adjustment, comprising:
an article of manufacture having a machine-readable storage medium that stores instructions which, when executed by a computing device, cause the computing device to
measure acoustic properties of a room containing a loudspeaker array,
determine a first directional property for processing to produce a directional pattern from the loudspeaker array according to the measured acoustic properties,
m

Assignees

• Apple Inc

Inventors

• Holman Tomlinson M

Classifications

• G10K15/08

  Arrangements for producing a reverberation or echo sound {(modifying acoustic properties to change reverberation time G10K11/002)} · CPC title

• H04R1/403

  loud-speakers · CPC title

• G10L25/78

  Detection of presence or absence of voice signals (switching of direction of transmission by voice frequency in two-way loud-speaking telephone systems H04M9/10) · CPC title

• H04S7/305

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

• H04R29/002

  Loudspeaker arrays · CPC title