What Will Block a Bluetooth Signal?

Because many Wi-Fi access points use the same 2.4-GHz bandwidth as Bluetooth, they can often interfere with each other to the point where your Bluetooth device may not work properly. Most routers have an option to switch to the 5-GHz frequency. Other Bluetooth devices can also interfere with signals, so sometimes it's necessary not to be using several Bluetooth devices at once. Some cordless phones also operate on these frequencies, as do wireless speakers, cameras and wireless baby monitors. Some LCD monitors can also interfere, not because they use wireless technology, but because they can emit harmonic interference in the 2.4-GHz band, especially when you're using a laptop with the lid closed and an external monitor directly beside it.

All electrical devices radiate RFs, but some do more than others. A microwave oven is a prime example of an unintentional RF radiator. If you turn on a microwave oven while using a Bluetooth device, it can interfere with the signal and, in some cases, block it entirely. Power lines, power stations and electrical railroad tracks can also emit enough RFs to disrupt Bluetooth. If you notice your Bluetooth begins to act up when operating an electrical device, turn it off or try moving farther away from it. Another option is to shield your Bluetooth signal from using physical objects known to disrupt RFs.

Some physical objects can interfere with RFs more than others. In the case of Bluetooth and Wi-Fi signals, the worst culprits are metal objects like filing cabinets, metal doors, refrigerators and even metal studs in walls. Plaster, concrete and bulletproof glass aren't as bad as metal, but can still interfere with Bluetooth signals, particularly if the objects are thick and the Bluetooth signal is weak. Water, bricks and marble have a medium capacity for blocking Bluetooth. At the bottom of the list are wood, glass and synthetic materials like plastic.

The 2.4-GHz band used by Bluetooth and Wi-Fi is 83-MHz wide, which gives a Bluetooth device the ability to hop between 79 different 1-MHz channels within that band. When Bluetooth detects interference on one channel, it can hop to another channel to try to avoid the interference. During this hop, the signal may be degraded or temporarily blocked, depending on what kind of connection the Bluetooth device relies on. In the case of voice services, like a Bluetooth headset, the disruption could cut out your sound when data packets are lost in the midst of a hop.