A microspeaker is usually selected for one primary purpose: producing sound.

USound MEMS speakers can extend that role beyond audible audio. Conamara provides wideband operation into the ultrasonic range, with a flat ultrasonic response extending up to 80 kHz. This makes MEMS speakers relevant for ultrasonic sensing and premium audio, enabling applications such as wear detection, sensor-free acoustic biosensing, distance and proximity sensing, human presence detection, and 3D positioning.

These applications are not limited to hearables. They extend from earbuds and smart glasses to laptops, displays, smart appliances, and other consumer or industrial devices.

MEMS speakers for ultrasonic sensing: beyond premium audio

The same MEMS speaker platform used for audio can also generate ultrasonic signals.

Many conventional ultrasonic emitters are optimized for a single operating frequency. Conamara instead combines a compact 5.0 mm × 1.50 mm package with wideband ultrasonic operation. Its bandwidth allows engineers to select the operating band, transmit complex signals, and adapt the waveform to microphones, mechanical systems, and environmental conditions.

For sensing applications, the MEMS speaker acts as the acoustic emitter. A microphone receives the transmitted signal or returning echoes, while signal-processing algorithms interpret the response.

This enables the same transducer platform to support several different acoustic functions.

Wear detection

In smart glasses, earbuds, and other wearables, ultrasonic signals can be used to determine whether the device is correctly positioned on the user.

USound describes this as a sensor-free approach that uses the MEMS speaker to detect wear without adding a separate proximity sensor.

In an audio device, the speaker can therefore reproduce sound while also providing the ultrasonic signal required by the wear-detection system.

Sensor-free acoustic biosensing

Ultrasound can also be used to obtain physiological information from inside the ear.

USound’s AuriSense platform uses a MEMS speaker to emit ultrasonic signals while audio continues to play. The returning ultrasound is captured by an existing inward-facing ANC feedback microphone. 

The system uses audioplethysmography (APG). Ultrasonic signals detect subtle changes in ear-canal volume caused by blood-vessel movement, generating an acoustic signal from which cardiovascular information, such as heart rate, can be derived.

Because AuriSense uses existing audio components, the architecture does not require dedicated photodiodes, infrared proximity sensors, or additional receivers for these functions.

This means the same MEMS speaker can operate simultaneously as an audio transducer and as the ultrasonic emitter within an in-ear biosensing system.

Human presence detection

Ultrasonic sensing also extends beyond wearable devices.

For camera-free human presence detection, a Conamara MEMS speaker transmits an inaudible ultrasonic signal into the space in front of a device. A microphone records the returning echoes, and signal-processing algorithms determine whether a person is present.

Applications include laptop and monitor wake-up, smart appliances, television and display presence detection, and workspace energy management.

Because the approach does not rely on camera images or ambient lighting, it can provide presence information without capturing or processing images.

Distance and proximity sensing

The same ultrasonic platform can be used for distance and proximity measurements.

USound identifies range measurement and proximity-triggered interaction as potential applications in compact consumer and industrial devices.

The MEMS speaker can therefore also serve as a compact ultrasonic emitter in systems that require acoustic ranging.

3D positioning

Wideband ultrasonic signals can also support localization and navigation.

USound describes the use of timing and phase information for positioning algorithms. Conamara’s ultrasonic characteristics include an omnidirectional sound field and support for complex waveform playback.

These characteristics allow the speaker to provide the acoustic signals required by positioning systems while maintaining a compact form factor.

One MEMS platform, multiple acoustic functions

The common element across these applications is wideband operation.

Depending on the system architecture, the same MEMS speaker technology can support:

• audible audio reproduction,
• wear detection,
• sensor-free acoustic biosensing,
• human presence detection,
• distance and proximity sensing,
• and 3D positioning.

The speaker does not perform these sensing functions alone. Microphones, electronics, and signal processing remain part of the system. Its role is to provide the acoustic excitation required for these functions.

This is what extends the role of the MEMS speaker beyond conventional audio: the transducer becomes part of a broader acoustic platform for both audio and sensing.

From audio component to system enabler

Premium audio remains an important application for MEMS speakers, but wideband ultrasonic operation opens additional possibilities.

In hearables, the same acoustic hardware can support audio, wear detection, and in-ear biosensing. In laptops, displays, and appliances, ultrasound can enable camera-free presence detection. In consumer and industrial systems, it can support proximity sensing and acoustic positioning.

One compact MEMS platform can therefore contribute to very different functions depending on the surrounding system architecture.

For engineering teams exploring audio, biosensing, ultrasonic sensing, or combinations of these functions, USound can support discussions around transducer selection, drive electronics, and acoustic system architecture.