Listening devices have become smaller, cheaper and easier to hide. They are now readily available both online and in electronic stores. To completely sweep your home or office for listening bugs, you'll need a radio frequency detector and other equipment. However, you can use a baby monitor to perform a limited sweep. A baby monitor will detect any listening device operating on the same frequency as the monitor. Most baby monitors use 49MHz, 900MHz, 1.9GHz or 2.4GHz. However, listening devices can broadcast your conversations from 3KHz to 12.5GHz and usually avoid using the frequencies commonly used by consumer devices.
Turn off all wireless devices in your home such as cordless telephones, wireless toys, computer networks, Bluetooth devices, radios and microwaves. These devices can also interfere with the baby monitor.
Walk slowly through your home or office carrying the baby monitor. If the monitor has more than one frequency, slowly cycle through all available frequencies.
Listen for any beeps or distortions with a repeating pattern, which would indicate the presence of a listening device. The noise should get stronger as you get closer to the device emitting the signal.
Baby monitors operate on limited frequencies and will not detect all listening devices. Most listening devices do not transmit data on frequencies commonly used by consumer electronics to avoid detection.