Apple is always looking for ways to improve the speakers in its iPhone and iPad line-up. One possible way, as evidenced by a newly granted patent (number 11,026,018), is via an “audio speaker with back volume containing adsorptive material.”
The problem with smartphones and smaller tablets is that, due to their small form factors, the integrated audio speakers may be micro speakers, also known as microdrivers, that are miniaturized implementations of loudspeakers having a broad frequency range.
Apple says that, due to their small size, micro speakers tend to have limited space available for a back volume. What’s more, given that acoustic performance in the low frequency audio range usually correlates directly with the back volume size, micro speakers tend to have limited performance in the bass range.
However, Apple says that the low frequency acoustic performance of portable consumer electronics devices having micro speakers may be increased by increasing the back volume size as much as possible within the internal space available in the system enclosure.
Here’s the summary of the patent: “An audio speaker having a speaker housing surrounding a back volume that is divided into a rear cavity behind a speaker driver and an adsorption cavity separated from the rear cavity by a permeable partition, is disclosed. More particularly, the adsorption cavity may be defined between the speaker housing and the permeable partition, and may be directly filled with adsorptive particles to adsorb gas during sound generation. The permeable partition may allow the gas to flow between the rear cavity and the adsorption cavity, and may retain the adsorptive particles within the adsorption cavity. Other embodiments are also described and claimed.”