I'm trying to make a cat purr noise but I'd like to do it more mechanically than using a sound file. It needs to fit into a box you can hold in your hand. I'm thinking of using a slow motor with a fan that flaps against a serrated edge but how can I get it low hertz like a cat? Thanks in advance for any ideas.
Not mechanical, Voice Recorder Device Very High Quality with Play Back for Stuffed Animal Inserts and Craft Projects: