This Raspberry Pi-Powered Passive Sonar Turns Two Microphones Into a Speed-Monitoring Station
An electrical engineer named Gregory has developed a low-cost solution for monitoring vehicle speeds using passive sonar. By leveraging the noise produced by tires on the road, Gregory created a system that calculates the speed of passing cars without the need for radar or active sonar. The setup consists of two microphones placed apart from each other, capturing the sound waves and calculating the phase difference.
To keep costs down, Gregory opted for a Raspberry Pi computer with a USB sound card, utilizing GNU Radio for audio sampling and signal processing. The system showed promising results during initial tests, accurately measuring the speed of passing vehicles. However, there are limitations to this approach, including variations in the speed of sound due to weather conditions and challenges in detecting vehicles that are either extremely slow or fast-moving. Additionally, filtering out other environmental noises can present challenges in obtaining accurate readings. If you re interested in projects concerning microphnes then I’d reccomend another article from the PiShop website on Creating a DIY Voice Assistant with Mycroft AI and a Raspberry Pi 4
Despite these limitations, Gregory’s low-cost passive sonar approach provides an alternative solution for speed measurement without the need for signal painting on vehicles. This innovation opens up possibilities for monitoring vehicle speeds in various settings while maintaining affordability and simplicity in the hardware setup. The full write-up is available on Gregory’s Hackaday.io page.
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