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Recording / measuring sound inside a helmet
Old 4 weeks ago
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🎧 15 years
Recording / measuring sound inside a helmet

My goal is to record and/or measure both sound pressure levels and frequency spectrum inside a motorcycle helmet, ideally right next to the ear while the helmet is being worn (while the motorcycle is being ridden). Not much physical space in there. Would love to hear some thoughts regarding some good ways to approach this... both technique and also gear recommendations (specific microphones, measurement devices, etc).

Not necessarily so concerned about measuring wind noise on the helmet, mainly concerned about measuring and comparing the engine / exhaust noise of different motorcycles with different exhaust systems, etc. Thus, the measurement device / microphone perhaps does not need to be inside the helmet next to the ear, but could maybe be inside of a separate wind-screened "pod" that could be temporarily attached just outside the helmet (?).

Though, if there was an accurate measuring device / microphone that was so small it could be squeezed inside the helmet next to the ear, that would be ideal... something like a small earbud, but instead of being a speaker, it would be a microphone.

I realize that the helmet itself will have an effect on the engine / exhaust SPLs and frequencies reaching the ear (helmet itself may resonate or cause reflections etc), so really the measurements should be taken inside the helmet in the proper riding position, but if this is nearly impossible to achieve, I'd be happy with the very next best possible approach.

Ultimate plan is to modify some exhaust systems to quiet them down at highway cruising speeds (dreaded exhaust "drone"), it seems it will largely be a trial and error project and I hope to have a way of comparing results. Again, both frequency spectrum as well as decibels will be compared.

Thank you
Old 4 weeks ago
Gear Guru
Contact Audio Precision in Oregon. They have developed several testing means for headphones and other devices. They also make the best audio test gear in the world.
Old 4 weeks ago
Gear Addict
🎧 15 years
I'd try Bruel & Kjaer who are probably the best in the world when it comes to acoustic transducers and measurement. Maybe something based around their HATS equipment might work. They've almost certainly supplied equipent for what you have in mind and would be able to advise on what to use or perhaps who to talk to who might be set up for doing the tests you want. Perhaps a Neumann dummy head setup with some mini mics like the DPA406_ series mounted in the outer ears might work - or use the head with the internal mics and get them checked for calibration first.

One obvious source would be the Institute of Sound & Vibration Research at the University of Southampton

There are loads of other useful studies on the subject of motorcycle noise, such as:

Salford University Automotive Testing

Paper: "Motorcycle Noise and Active Noise Reduction", Charles H Brown & Michael S Gordon. University of S. Alabama & William Patterson University. The Open Acoustics Journal, 2011

Paper: "Noise mechanisms in motorcycle helmet noise", Michael Carley, University of Bath, UK; Nigel Holt, Bath Spa University, UK; Ian Walker, University of Bath, UK. Proceedings of Meetings on Acoustics, Acoustical Society of America (ASA), April, 2010

Article: Experimental evaluation on noise reduction performance or a motorcycle helmet. M.S. Ozer, F. Terzioglu, International Journal of Automotive Engineering and Technologies. 2019

A quick web search will turn up quite a lot of reading.
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