Vibration sensor makes vehicle interior quieter

Vibration sensor makes vehicle interior quieter

New Products |
By Christoph Hammerschmidt

STMicroelectronics is setting the stage for more acoustically comfortable cars by suppressing road noise (RNC) with Active Noise Control (ANC). With the development of the MEMS-based vibration sensor AIS25BA, the semiconductor manufacturer is reacting to the change in the demands placed on vehicles by customers: Instead of engine performance and sportiness, comfort is increasingly becoming the decisive purchase criterion for vehicle users.

Electric vehicles are already inherently quieter than vehicles with combustion engines, so car manufacturers are now focusing on reducing the noise level inside the vehicle generated by the wheels or vibrations. The aim of these measures is to provide passengers with a more pleasant driving experience through a quieter environment.

Noise cancellation algorithms, using multiple sensors distributed throughout the vehicle, measure ambient noise and eliminate vibrations using noise cancellation waves that act as a compensating counter-sound.

According to the manufacturer, the sensor offers the lowest electrical noise on the market, helping vehicle designers reduce noise levels in the vehicle to the lowest possible level. In addition, the sensor offers the fast response and low latency that the RNC system needs to calculate the correction signals in real time. Last but not least, it offers the necessary bandwidth to detect disturbing noises in the entire spectrum of sound waves relevant for the application. Moreover, thanks to its wide temperature range and great mechanical robustness, the sensor is suitable for the most demanding installation locations found in today’s vehicles, namely close to the engine or the (electric) drive as well as near the wheels and the wheel suspension.

At 30 µg/√Hz (X- and Y-axis) and 50 µg/√Hz (Z-axis), the AIS25BA 3-axis accelerometer has an extremely low noise density, up to 58% better than the best competing products.

As a result of these outstanding noise characteristics, the frequency response extends to 2.4 kHz, covering the complete spectrum relevant for noise compensation in the vehicle interior. The sensor’s total latency of 266 µs is said to allow the system enough time to generate the necessary noise compensation signals in real time.

The sensor is equipped with a time-division multiplex (TDM) digital interface that allows the system to synchronise the outputs of multiple accelerometers distributed throughout the vehicle to measure vibrations. The audio-friendly interface also allows easy connection to other types of data buses that have become widely used in the automotive sector. The total measuring range can be set to values up to ±7.7 g, which provides sufficient reserves in view of the high vibration levels typical of the application. The operating voltage range is 1.7 V to 1.99 V.

The AEC-Q100-compliant AIS25BA is available now in a 2.5 mm x 2.5 mm x 0.86 mm LGA package with 14 connectors and costs from $3.90 (from 1,000 units).

More information here


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