- Tue Mar 10, 2015 12:44 pm
#180359
I need to record urban environmental noise unattended for up to one week, to measure dB levels and extract incident sound clips through post processing. eBay and Amazon are awash in pen drive recorders, reviewed at: http://www.chucklohr.com/usbaudiorecorder/ . The minimalist approach and small concealable format are attractive. So are the low prices, since theft can be a threat. Unfortunately there are serious design flaws.
1) Lossy compression -- mostly ADPCM -- distorts noise not conforming to assumptions, can't ensure accurate recovery of dB levels.
2) Internal soldered-in rechargeable batteries poop out after 10-15 hours, aren't field-replaceable.
3) Largest storage capacity, 8GB, is too small for a week of uncompressed WAV.
4) Dynamic range -- approximately 10 to 100 dB needs shifting up ~30 dB for noise levels of interest.
Closing this gap would make addressing urban noise pollution and nuisances (e.g. noisy neighbors or loud motorcycles) much more tractable. Prevailing solutions are ~$5,000 monitoring stations, sometimes with additional expense for hardening. Alternative cheap stealth solutions now seem very feasible!
Design goals:
1) Low cost so theft is bearable. Initial target is $20.
2) Small, concealable, weatherproof package to hang from tree limbs or velcro to surfaces.
3) Record uncompressed 16 bit WAV, 22,050/24k and 44,100/48k sample rates selectable in setup file.
4) Power requirement low enough for one week with three or less AA cells or ~2,000 mAh lithium rechargeable. Option to power from A/C via 5 volt USB charger.
5) Removeable media, e.g. microSDHC, up to 32GB.
6) Segment files on exact hour boundaries with date/time stamping.
7) Dynamic range 30-120dB
8) Hardware and software are open source.
1) Lossy compression -- mostly ADPCM -- distorts noise not conforming to assumptions, can't ensure accurate recovery of dB levels.
2) Internal soldered-in rechargeable batteries poop out after 10-15 hours, aren't field-replaceable.
3) Largest storage capacity, 8GB, is too small for a week of uncompressed WAV.
4) Dynamic range -- approximately 10 to 100 dB needs shifting up ~30 dB for noise levels of interest.
Closing this gap would make addressing urban noise pollution and nuisances (e.g. noisy neighbors or loud motorcycles) much more tractable. Prevailing solutions are ~$5,000 monitoring stations, sometimes with additional expense for hardening. Alternative cheap stealth solutions now seem very feasible!
Design goals:
1) Low cost so theft is bearable. Initial target is $20.
2) Small, concealable, weatherproof package to hang from tree limbs or velcro to surfaces.
3) Record uncompressed 16 bit WAV, 22,050/24k and 44,100/48k sample rates selectable in setup file.
4) Power requirement low enough for one week with three or less AA cells or ~2,000 mAh lithium rechargeable. Option to power from A/C via 5 volt USB charger.
5) Removeable media, e.g. microSDHC, up to 32GB.
6) Segment files on exact hour boundaries with date/time stamping.
7) Dynamic range 30-120dB
8) Hardware and software are open source.