Apple researching earphones with embedded pressure sensors for better sound

An updated patent filing published Wednesday suggests Apple is revisiting a pressure-sensing earphone design that promises to deliver higher quality sound by customizing output based on a user's ear size.

Apple's patent application for "Pressure sensing earbuds and systems and methods for the use thereof" makes a number of claim modifications to the original grant issued in 2011 by the U.S. Patent and Trademark Office, though both filings describe a system by which an earphone delivers optimized sound on a per-user basis.

Standard in-ear headphones, including Apple's EarPods, do not achieve an airtight seal with a user's ear canal, which in turn affects acoustics. While not technically a degradation of sound quality, and barring outside factors like ambient noise, an earphone's frequency response changes depending on how well it seals with surrounding skin.

To compensate when an earphone doesn't quite fit, Apple proposes a product capable of dynamically altering volume levels over a range of audible frequencies based on ear size. Instead of manually measuring a user's anatomy, the patent estimates dimensions informed by data from pressure sensors embedded in an earphone, earbud or over-the-ear headphone.

In some embodiments Apple calls for the use sensors made from a class of elastomeric material called Quantum Tunneling Composites. When force is applied to a QTC, its electrical resistance drops proportionally in known quantities, meaning said force can be measured. Other suitable sensors include piezoelectric or capacitive units.

Depending on earphone type, QTC pressure sensors are arranged in a pattern where they are most likely to come in contact with a user's ear. Measuring changes in force, or lack thereof, provides a rough estimation of ear size that can be used to process volume output. In some cases, the system constantly refreshes pressure readings to dynamically adjust levels.

To ensure an earphone delivers a consistent audio experience for different size ears, an onboard processor matches incoming pressure data with an index of optimal aural profiles, attenuating output to achieve the desired frequency response. This library allows for either general "small, medium, large" adjustments or fine tuning, depending on system sensitivity and user preference.

As for Apple's claim changes, the company is now protecting embodiments covering occluding (sealed) earphones and over-the-ear headphones where it previously only claimed non-occluding earbuds. While not proof that such a product is nearing market, the tweak in wording opens the door to speculation, especially considering Apple's purchase of headphone maker Beats.

Apple's pressure-sensing earphone patent application was first filed for in May 2015 and credits Jonathan Aase as its inventor.