Apple exploring multi-channel dynamic sound for iPad-like devices

A new Apple patent application published by the U.S. Patent and Trademark Office this week shows a portable device, like an iPhone or iPad, with more than just one speaker included in the device. The application, uncovered by AppleInsider, describes using an orientation sensor to adjust sound on the device, much like the screen rotates when an iPad is rotated.

The current iPhone and iPad have only one speaker on the bottom of the device. Apple's proposed invention shows a device with as many as four discrete speakers, allowing for sound that could go even beyond two-channel stereo.

Entitled "Audio Channel Assignment for Audio Output in a Movable Device," the application describes an audio processor that is coupled to the speakers on the iPad. Much like the screen adjusts to any manner on the orientation-neutral iPad, this would allow the sound to be heard correctly by the user no matter how they hold the device.

"People generally have a well-developed ability to localize the position of a sound source based on the differences in the way the sound is heard by their two ears," the application reads. "In sound reproduction, sound may be recorded in two or more channels of audio material and routed to multiple speakers to provide sound cues that allow the listener to localize the apparent position of the recorded sound."

It notes that multiple speakers can create the illusion of localized sound sources, but this task becomes more difficult when attempted on a mobile device.

The use of multiple speakers on a device like the iPad could also address an issue where, if held improperly, a user's hand can cover the hole in the device where the sound comes out, potentially suppressing it.

The application, made public this week, is credited to Heiko Panther, David Julian and Roberto G. Yepez. Apple first filed for the proposed invention with the USPTO on July 6, 2009.

The filing is revealed as Apple is believed to be preparing to release its second-generation iPad with a larger speaker on the newly revised hardware. Leaked cases purported to fit the new iPad show a large opening on the rear left side of the device, and one mockup portrayed that space with a speaker grille on the back.

Those cases were made available for sale on a business-to-business trading site, but were removed after the site received a "legitimate takedown request." That legal action could signal that the cases are in fact authentic and representative of the new iPad's design.