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RadioReference.com Forums
Okay, so I have an Acoustic Research wireless audio system sitting around the house. It's a two part system, an audio transmitter that plugs into an mp3 player or something, and a wireless speaker so you can bring music around the house, yard, whatever.
I saw a sticker on the bottom of the transmitter that said 900MHz and I thought it would be fun to listen to the signal through my sdr dongle, so I did. It seems to just be an FM transmitter, and sounds great on the computer. Cool. What was strange was when I unplugged my iPhone and picked up the transmitter. I heard a "BOOM" in my computer speakers just as I touched the device. Well I played around tapping it for a bit and noticed if I speak loud enough near the transmitter I could hear my voice in the transmission!
Is this some kind of interference or is there actually a hidden microphone in this thing???
At around 12 seconds you can hear me say "testing 123" and tap a couple time before and after that. Sorry for the zip file, the forums wont let me share an mp3 or wav...