Automotive-qualified MEMS microphone - The car is all ears

11/08/2023 Know-How

Cars are learning to listen – not only in the passenger compartment but also in their external environment. Since acoustic signals from the vehicle environment can provide key information about other road users, thereby enhancing the ever-increasing driver assistance systems and automated driving features.

Microphones have become the norm in vehicle interiors; all newer vehicles are equipped with at least the mandatory eCall system for audio communication in the event of an emergency. New applications are now being added, such as:

  • Active noise cancellation (ANC) by producing a counter sound wave
  • Recording of the road condition
  • Spectrum analysis of engine/driving noise for preventive maintenance as well as condition and fault detection
  • Detection of emergency vehicles with their siren turned on, including direction recognition

Infineon’s AEC-Q103-qualified IM68A130A MEMS (microelectromechanical system) microphone is all ears when it comes to helping: It provides an analog output signal and features an integrated low-noise preamplifier (Fig. 1). As a result, it achieves a low noise floor of only –106 dBV(A) and a high signal-to-noise ratio of 68 dB(A). At the same time, the limit for the acoustic overload point is at 130 dBSPL (sound pressure level). These performance characteristics contribute to a wide dynamic range for acoustic signals and provide intelligibility and signal fidelity for both very quiet or distant sounds and very loud or close sounds.

Together with a straight frequency response of between 10 Hz and 16 kHz, IM68A130A features excellent recording quality.

For voice recognition algorithms, the MEMS microphone provides processable data thanks to its high signal-to-noise ratio. Thus, even quietly spoken commands result in a good signal. When used outside the vehicle, the high signal-to-noise ratio favors picking up sound from a distance, for example approaching emergency vehicles with their sirens turned on.

Multiple microphones for more options

Using multiple microphones at the same time opens up further options. Since in a microphone array, the sound from one source arrives at the individual microphones with varying intensities and time offsets. The direction of the sound source can be inferred from the difference in the signals. Digital signal processing can then be used to set a desired directional characteristic from the microphone array signals (beamforming). Thanks to its narrow tolerances for sensitivity and phase response, IM68A130A is also ideally suited for use in arrays.

Faster time to market with the A2B evaluation kit

When it comes to testing and optimizing such an array with multiple automotive-qualified MEMS microphones, Infineon’s A2B evaluation kit is the ideal choice. It contains all the components required for a multi-microphone system networked via A2B bus (Fig. 2). Each slave module accommodates four microphones. The packages of the slave modules are magnetic and adhere to the sheet metal of the vehicle body (Fig. 3). A 32-bit Aurix series microcontroller in the master unit is responsible for digital signal processing. Sample software for various configurations (different number of slaves or active microphones in a slave) is also included in the evaluation kit.

Target applications for the A2B evaluation kit contain siren detection, hands-free or voice control, as well as beamforming and active noise cancellation.


The more human – and other – senses the vehicle adopts, the greater the advances in the automation of driving. Infineon’s high-performance analog xenon MEMS microphones, e.g. IM68A130A, can ensure a sense of hearing for acoustic environment detection. Rutronik’s portfolio additionally includes further sensors for automotive use that pave the way for autonomous driving.


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The IM68A130A MEMS microphone in the TLGA package.

The A2B evaluation kit from Infineon and its components: (1) ECU master unit with microcontroller from the Aurix series, (2) package, (3) 12 V plug-in power supply, (4) one of up to four slave modules, (5) magnetic package for a slave module.

Example of the distribution of four slave modules on the vehicle’s exterior.