Today the U.S. Patent and Trademark Office officially granted Apple a patent titled "Surround sound rendering based on room acoustics" that relates to performing audio processing techniques upon a sound program to render the sound program for output through one or more loudspeakers.
Loudspeaker arrays may generate beam patterns to project sound in different directions. For example, a beamformer may receive input audio channels of a sound program (e.g., music) and convert the input audio channels to several driver signals that drive transducers (or drivers) of a loudspeaker array to produce one or more sound beam patterns.
Apple's granted patent covers a method performed by a programmed processor of an audio system within a room that includes a first loudspeaker that has a first loudspeaker beamforming array of two or more loudspeaker drivers and a second loudspeaker that has a second loudspeaker beamforming array of two or more loudspeaker drivers.
The system obtains a sound program as several input audio channels. For example, the sound program may be a soundtrack of a movie that is in surround sound 5.1 format (e.g., having five input audio channels and one low-frequency channel). The system performs a beamforming algorithm based on the input audio channels to cause each of the first and second loudspeaker beamforming arrays to produce a front beam pattern and a side beam pattern when the loudspeakers are close to an object within the room (e.g., within a threshold distance). In this case, the front beam patterns are directed away from the object and the side beam patterns are directed towards the object.
As a result, the different beam patterns may include different portions of the sound program. For instance, in the case of the sound track, the front beam pattern may include a center channel (that has dialogue), while the side beam pattern may include portions of the surround channels (left surround channel and right surround channel). The system, however, may perform a cross-talk cancellation (XTC) algorithm based on a subset of the input audio channels to produce several XTC output signals for driving at least some of the drivers of the loudspeakers when the loudspeakers are far away from the object (e.g., exceeding the threshold distance).
Apple's patent FIG. 1 below shows an audio system that includes a loudspeaker with a loudspeaker array of two or more loudspeaker drivers; FIG. 2 shows a room with several loudspeakers configured to output sound according to one aspect.
Apple's patent FIG. 3 above shows a block diagram of an audio system that performs different audio processing techniques upon a sound program of one aspect of the disclosure.
For more details, review Apple's granted patent 10,945,090.