The U.S. Patent and Trademark Office on Thursday published an Apple patent application covering an active system that protects sensitive acoustic components like microphones and speakers from damage.

As the state of smartphone technology advances, so do the internal components being used in their construction, including increasingly sensitive — and increasingly small — electronics like acoustic sensors and emitters. While mesh grilles and foam were sufficient in protecting previous generations of devices, future smartphones may require more active measures.

Apple's filing for "Active protection for acoustic device" describes a mechanical system that takes input from motion sensors, as well as other internal measurement devices, to actuate a shutter or valve that closes off an acoustic component's passage. Once closed, the sensitive acoustic device is protected from sudden changes in pressure, air bursts and acoustic shock, among other threats.

As noted in the filing, the acoustic components can be microphones and speakers disposed on the front face of a portable device, as well as the bottom, down-firing configuration seen in the iPhone. An acoustic passage serves to direct and in some cases amplify or resonate audio waves into and out of the device.

At the same time, these passages can be detrimental when a phone is dropped, as an unwanted pressure event could rupture or otherwise damage the acoustic part. Scenarios of an air burst may include a face-down drop or exposure to high-intensity external acoustic fields like extremely loud music.

Source: USPTO

Apple's invention proposes the device use onboard sensors, such as an accelerometer or gyroscope, to sense an impending fall or shock event. With the information, the system can activate a mechanism to close or seal the acoustic passage prior to contact.

In some cases, the acoustic component itself can sense heightened pressure levels and actuate the mechanism to fully or partially seal off the passage accordingly. This particular embodiment relies on generating an audio signal, opening the protection mechanism to sample said signal and measuring it against a threshold indicative of being over a predefined pressure differential.

As for the closure system, the filing describes a shutter or valve setup that can be operated by solenoids to seal the outer acoustic port or inner acoustic passage. In another embodiment, a solid state system incorporates a microelectromechanical system (MEMS) via gear drive, stepped motor or other applicable mechanism. Both variations rely on a control signal from either the motion sensor array or audio tests described above.

Illustration showing open (left) and closed protection mechanism.

As Apple's devices become more advanced with multiple microphones for noise canceling, multiple speakers for stereo sound and other acoustic enhancements, there may soon come a time when an active protection system is needed.

Acceleration in miniaturization techniques and demand for high-quality audio could push the company to release such a mechanism in the not too distant future, though Apple is not expected to immediately incorporate the technology into its iOS device lineup.