The 8,767,994 patent patent describes a design common to existing "plasma speakers," which use a light gas such as helium behind the speaker's vibrating cone.
The use of a specific gas, rather than outside air, results in a more precise reproduction of high fidelity sound. However, existing gas filled speaker designs only work well in specific installations where the surrounding barometric pressure can be controlled.
In order to make the technology relevant for mobile speakers, such as those in a smartphone or in headphones, there needs to be a way to adjust the gas pressure in concert with slight changes in ambient air pressure, such as when taking an elevator up into a building.
An abrupt change in air pressure can "result in a net force being exerted on the diaphragm of the sealed speaker system, causing it to 'stick' and therefore stop producing sound until the pressure inside the speaker has equalized with the barometer pressure," the patent notes.
"In air speaker systems, such barometric equalization is achieved relatively quickly (in order to prevent noticeable sticking of the diaphragm), by adding a small vent hole to the enclosure (at the expense of a small amount of sound quality degradation). This solution however will not work for an enclosure that is filled with gas and no air."
The design in the patent grated today uses a vented cavity that allows ambient air to compress the gas via a gas-proof barrier, compensating for changes in the surrounding air pressure. The patent also describes how such a design could be manufactured.
Apple has long had an interest in advancing the state of the art in speaker designs for mobile headphones, but its plans have garnered more attention following the announcement that it would be spending $3 billion to acquire Beats, a popular brand of premium priced headphones.
The use of patented new technology capable of reliably reproducing significantly better sound quality, combined with the use of Apple's Lightning digital interconnect for mobile devices to deliver higher quality sound, could be leveraged to drive sales of both audio equipment and higher quality audio content in iTunes.