A sound module does four jobs: it stores audio, waits for a trigger, amplifies the signal, and drives the speaker. None of it is complicated, but each part shapes what you can do with the product.
1. Audio storage
- OTP (one-time programmable) chips are programmed once at the factory and can’t be changed afterward. They’re the cheapest option there is, and perfect when the message never changes — a jingle, a “thank you,” a fixed greeting.
- Flash-based chips can be re-recorded by the end user. Typical sizes are 6 seconds, 10 seconds, 20 seconds, or 30 seconds; longer models stretch to 3–4 minutes. This is the type that makes “record grandma’s voice” products possible.
- SD-card and USB modules play MP3 files from a card or from onboard memory (16 MB is a common starting point), and you can download audio straight from a PC. These are the ones to pick when you need real playback length.
2. Trigger
The module sits there doing nothing until something tells it to play. Five triggers cover almost every product on the market, and they’re in the table below.
3. Playback
A small amplifier drives the speaker — a 40 mm plastic speaker is the workhorse on compact modules. Pre-recorded versions accept MP3 or WAV: send us the audio file, we burn it in at the factory, done.
4. Power
Most modules run on three AG13 button cells that users can replace themselves. Others take CR-series coin cells, AAA batteries in a separate box, or a rechargeable USB battery for the fancier gift market.