I'm new to this world though I was invloved in electronics many years back in school. I now work for the Fire Service/Search and Rescue. I'd like to be able to make a remote operated noise maker to use in victim locating exercises to replicate a buried victim making knocking noises. If the device could also play recorded noises such as cries for help, all the better. Does anyone have a project like this already or does anyone have any hints on how to build it?
I’d go with a MP3 player module and SD card, for playback of the recorded noise. Mixing multiple noise sources is still more complicated, because the ordinary 8 bit controllers can not process audio data streams in real time. A RasPi may better fit your needs.