[djeiasbsbo]

For some simpler projects, I can only recommend doing some digital signal processing. For example, an audio signal is just a list of values, so you can do things like:

- Count the number of zero crossings - Find out where they are - Create any shape of wave by adding together multiple sine waves - Hard clip the signal - Stretch a signal and interpolate it with new samples - Invert and revert a signal

For level 2, you can start processing "live":

- Create a sine synthesizer - Create a small ring buffer of samples - Find out how to output that audio (system audio, soundcard) - Add MIDI support - Add polyphony support

DSP gets hard once it has to be in real time and the latency has to be minimal. It's great exercise to mess around with it.

[jamil7]

I came across this area recently while trying to build an iOS app that could reliably detect knocks or taps on the body of the phone, I was ultimately unsuccessful but I learned a lot about collecting and analysing microphone and gyroscope data. Also built some nice tooling for collecting live iOS sensor data and transmitting it to prometheus/grafana over mqtt.

[djeiasbsbo]

That sounds interesting. A cool project would be to inspect gyroscope data when the iOS keyboard is in use. Maybe it would be possible to create a keylogger based on it.

I guess it would depend on how good the data is and which keyboard is being used.

I know that this is possible on Android.