Noise cancelling megaphone
|Project Noise Cancelling Megaphone|
First, it is not really a proper noise cancelling megaphone, but more of a speech/music-jamming one. Have a troublesome source of sound shut of by broadcasting the sounds back, but only perceptably delayed.
Ever encountered those useless type to cheap to buy a headset for their mp3-playing mobile? To add insult to injury their taste in music tends to be in the 'atrocious' part of the musical-taste-spectrum, often involving autotuned hip hop. This might be a solution.
Combine a directional microphone with a megaphone and a Raspberry Pi for the signal processing. Have the megaphone broadcast the sound collected through the directional microphone just a few milliseconds out of sync back to the source of your annoyance. Also works great on yapping dogs.
- Megaphone (about 30 USD on eBay)
- Directional microphone (also about 30 USD on eBay)
- Raspberry Pi, model A or B (model A goes supposedly for about 25 USD ex tax & shipping)
- Integrating the hardware, probably involving a custom microphone holder (probably 3D-printer) and some epoxy
- Weather- and fool-proof RasPi case
- Getting a RasPi Model A, they're not available yet
- Doing the signal processing software, has anyone ported PureData to ARM yet?
So if you have experience with Pure Data (http://puredata.info/) this may actually be trivial.
Actually this is not so much a project as a concept. I'm not going to execute it, but if anyone is willing to actually do it I might help funding the components. If you do: please have it airbrushed appropriately and have it available for events such as hacker camps and Chaos Congress.
Notes by smeding
I don't want to change the project myself, but here's my two cents: It's probably far cheaper and easier to implement the wanted effect using analogue electronics such as op-amps. It removes a lot of complexity from the signal processing chain, which should make it easier to get repeatable, wanted results.