As I cycled to work this morning, I had a crazy idea. It's just
daydreaming and will probably never happen, but I wondered if anyone on
the last has any useful/interesting thoughts.
I want to measure how fast I'm turning the pedals on my bike (the
"cadence") and synthesize/sample the sound of an internal combustion engine.
As far as I can work out, there are three major parts to this.
1. A sensor that can measure my cadence. A simple magnet switch that
triggers once a revolution won't be enough to measure the cadence with
sufficient resolution, since my cadence is usually between 50 and 80
rpm. I would probably need to mount multiple magnets spaced equally
around the chainwheel and have a single sensor on the frame. Then I have
to get it to supply this information to my control program.
2. I need a control program that can read in the input from my cadence
sensor and convert a cadence reading of "66 rpm" into a frequency that
should be sampled/synthesised, e.g. "500 Hz" (I'm making these numbers
up). It will also need to be able to somehow smooth out the readings,
perhaps by interpolation, so when I accelerate, the sound of the revs
climbing doesn't increase in obvious steps. It could also have other
logic, e.g. when my cadence is 0 rpm, the sound of the engine is idling
rather than off.
3. I need a synthesiser or sampler that can take an input from my
control program and make the sound of an engine (or more likely, a sine
wave to start with). I've never sampled or synthesised on a computer
before but this engine-specific sampling technology already exists in
video games, such as torcs.
I have absolutely no idea why I would want such a device - just for the
fun of building it, I guess. I would like it to work in realtime (rather
than later generating the soundtrack from recorded cadence data). The
thought of sitting at the traffic lights with my earphones in and then
hearing the mighty roar of a V8 as I pull away would be really satisfying...
Any thoughts - useful, interesting, humorous, or otherwise - are welcome!
Systems Support Specialist
ResNet | Wireless& VPN Team
University of Bristol
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