Bench Talk

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I love my electric car. One of its redeeming features is it runs very quiet. But as I drive along streets where pedestrians, sometimes joggers or kids walking to school, are engrossed in thought or distracted by their smartphones, I have to be extra vigilant. It can be a tense journey for a driver when you’re not certain they can detect your quiet-as-a mouse vehicle rolling toward them.

Before EVs or hybrids, most pedestrians seemed to be able to sense the running engine of even the most smooth-running gas-powered vehicle—perhaps because of the familiar sound or at least the smell of fuel coming from an internal combustion engine (ICE).

To address this, traffic safety agencies worldwide have sought to establish regulations requiring electric and hybrid vehicles to emit alert sounds to warn pedestrians when they approach. So far, quiet-car regulations have been recommended but not enacted. Automakers have recognized the issue and are working to make their EV and hybrid vehicles be more audible around pedestrians.

This week’s New Tech Tuesday looks at three STMicroelectronics boards that work together to evaluate Acoustic Vehicle Warning System (AVAS) applications for quiet-running vehicles. These boards are a step in creating audible warning signals for vehicles.

We're talking about the AEK-MCU-C1MLIT1 Evaluation Board, AEK-AUD-D903V1 Automotive Audio Amplifier Board, and AEK-CON-C1D9031 Connector Board. They're available as part of the AutoDevKit^™ with ready-to-run application firmware using the SPC5-Studio software.

When connected, these boards create and control audible motor sounds to alert pedestrians.

Individually, these boards have specific evaluation functions:

AEK-MCU-C1MLIT1 Evaluation Board: This board tests the SPC582B60E1 Power Architecture^® microcontrollers, which are designed to address vehicle body, gateway, and industrial-oriented applications.

AEK-AUD-D903V1 Automotive Audio Amplifier Board: This board evaluates the FDA903D digital amplifier, with load current monitoring and wide voltage operation range. The amplifier can also be interfaced with the SPC582B Chorus Automotive MCU to provide warning sounds.

AEK-CON-C1D9031 Connector Board: This board bridges the MCU-testing board and audio amplifier board.

With more electric and hybrid vehicles on the road, pedestrians will have to be more alert, and drivers will have to account for distractions. The goal is to have vehicles have a continuous noise level of at least 56dBA (within 2 meters) if the car is traveling 20km/h (12mph) or slower and a maximum of 75dBA. Acoustic Vehicle Alerting System systems will create warning sounds such as a traditional car horn that honks or ICE sounds.

If they alert one pedestrian who might be updating their social media while in a traffic crosswalk, it's worth it.