GreekGod wrote: 28 Jun 2026 01:15
Goodness, this is so good! Could you please share the specific equipment and apps that you have used? I have a contact mic ad well, but cannot figure it out yet - still getting no sound, even though it reacts to me tapping to it
Hi! Thank you!
This sounds exactly like what happened to me when I first bought the device. It turned out the wrong mode was selected. That's exactly how the probe mode behaves.
The device is called HY929 Leak Detector / wall microphone. There are different kits available; I got the basic one. It includes: the amplifier itself, the microphone (a cylinder with a small pin on a spring in the center), a probe (a thin metal tube with a hole that can be inserted into hard-to-reach places, for example when looking for noises in a car, under a door, or into a hole in the wall), and headphones.
This kit is suitable for listening but not for recording. That's why I separately bought a module that plugs into the amplifier. It's called the HY929 Recording Module. You insert a flash drive into it, and it plugs into the amplifier. It has a record button. The module automatically saves recordings in MP3 format to the flash drive.
The module is cheap, poorly assembled, and works strangely — the indicators aren't always accurate — but I learned how to use it since there weren't many other options. There's also the option to record sound through the headphone output directly into a smartphone, but I haven't tried that yet. I'm waiting for the necessary cables and adapters to arrive (I ordered them almost immediately after noticing the module was acting up). At the moment, though, the cables are no longer needed — everything works as is
The device has a mode switch. Middle (for thin and medium walls), Powerful (for thick walls), and a probe mode. There's also a volume knob on the amplifier — that's what initially misled me. It's not just volume; it's Gain, so you shouldn't crank it up too high.
Press the microphone firmly against the surface (be careful with it — once pressed, don't move it! The thin rod in the center will break if you slide the microphone across the wall). Press it, then secure it with something — furniture or some kind of prop (like a shower curtain rod, for example). Mode: middle. Gain slightly below the middle. That's all the settings. I didn't process the files in any way
The microphone cable and the amplifier itself basically act like antennas, so they pick up electromagnetic interference (EMI) and any noise from household appliances, even on other floors. A neighbor's robot vacuum moving around creates noise; a turned-on hair dryer creates noise again. I fought the EMI and mostly won. Ferrite Beads/Rings — clip them onto the wires and they almost eliminate EMI (not 100%, but they help a lot). You've probably seen those cylinders on old USB cables. Also, keep the amplifier and microphone away from any wires and devices. Even Bluetooth headphones lying nearby create noise
And another important thing is the wall material. Thin wooden walls or drywall = good recording, and you don't need to crank up the gain. Thick foam block walls = you'll most likely have problems with recording. In general, you just have to test it.
