Crown Audio by Harman




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Siren indicator for deaf drivers

I'm working on a system in which a microphone on a car picks up siren sounds in traffic. That siren signal is amplified, and is used to activate an LED inside the car when siren sounds are present. The goal is to warn deaf drivers (or hearing drivers) that sirens are active. Can you recommend a microphone and wind shielding for this application?
Helen Wright

Reply: Crown makes a model PZM-11LLWR weather-resistant microphone. It has a line-level output so you might not need to amplify it, and it runs off the car battery (12 volts DC). It is omnidirectional so it picks up in all directions. Price in www.froogle.com is $134 to $150 USD.

It has louvers in the faceplate that let sound in but keep water out. If you can mount the mic with its faceplate vertical rather than lying down, it should work fine. You will need to cover it with a windscreen. Maybe the mic could be mounted on the trunk of the car near the back window or wherever wind noise is minimal.

For the windscreen, you could construct a 12-inch diameter dome-shaped frame out of coathanger wires, and cover the frame with silk fabric. Put this dome over the mic, making sure the frame is well sealed at the bottom to prevent air leaks. The larger the dome windscreen, the better it rejects wind noise.

Note that if a human listener cannot hear a distant siren, neither can a microphone, because the signal-to-noise ratio is not high enough.

Here's a link to the PZM-11LLWR data sheet: