|Noise generation for sleep||
random trip report
You can get clock radios and other electronic gizmos that make 'nature sounds'. These all have chirpy bird sounds and 10-second cycles; they're completely intolerable. You can also buy analog devices (basically fans) for a lot of money (~$100). These have limited control for volume and none for frequency.
Tune a radio to noise between stations? Doesn't work - they all have muting circuits these days. I thought about building an electronic noise generator, but my skills aren't good. I'm a software guy; I can make audio CDs. But a CD is only 80 minutes; you can play it on repeat but then you get 10 seconds of silence. You could get 2 CD players and offset them; kludge.
As a stop-gap measure, we started running a small fan at night. This produced noise with a lot of low frequencies, and it kept me awake. Part of my brain interpreted the low frequencies as a truck that was about to run over the tent in which I was sleeping. I had to wear earplugs (uncomfortable).
We finally came up with a good solution. My stepfather Paul bought us a cheap ($50, Target) boom box that can play MP3 files on CD-ROM. I wrote a program that generates band-limited noise, in the form of a WAV file, converted this to MP3, burned a CD-ROM, and play it every night in the boom box. Works like a charm. With the MP3 compression, a disk can hold 16+ hours.
NOTE: the boom box turned out to have a skipping problem. Instead, I'm now using a Philips portable CD player, hooked up to a pair of amplified computer speakers.
My program (the source code is here) lets you control the center frequency and width of the bandpass filter. I used a band 500 Hz wide centered at 4 KHz; this is a nice hiss that my brain ignores after a few seconds. But you can try other parameters.
The key to getting a nice long MP3 file: generate the WAV files with 8-bit samples, in mono, at a low sampling rate. I used BladeEnc for MP3 encoding, and the lowest sampling rate it accepts is 32K. With these parameters, a 16-hour WAV file is 1.8 GB (you need to stay under 2 GB since most OSs don't handle big files), and the resulting MP3 file is 450 MB, which fits nicely onto a CD-ROM.
If you want a free copy of my noise CD-ROM, just let me know.