Just because you can buy something doesn't mean it works. You can buy a home gym, for example, but it won't make you thin. However, there are some things you can buy that won't work even if you actually try to achieve a result.

You buy devices that control pests using ultrasonic frequencies - they are purported to work for mosquitoes, cockroaches, ants and now there are new versions targeting bed bugs, since those were in the news a lot.

A new paper reports the results of tests of four commercially available electronic pest repellent devices designed to repel insect and mammalian pests by using sound. 

The devices, which were purchased online, were used according to manufacturers' instructions. A sound arena was created for each ultrasonic device, in addition to a control arena which featured no sound. However, the authors found that there were no significant differences in the number of bed bugs observed in the control (no sound) and sound arenas, and that bed bugs were neither deterred nor attracted to the arena with the sound device.

The authors conclude that the ultrasonic devices may not have deterred or attracted bed bugs because they don't really produce the right combination of frequencies. Bed bugs are commonly exposed to frequencies made by their host species (humans) and by appliances and machines found in homes. 

Therefore, it may be possible that bed bugs also would exploit sounds made by their human hosts, such as breathing or snoring. Future studies of bed bug bio-acoustics may be served well by using low-frequency sounds produced by host species.

Paper: "Efficacy of Commercially Available Ultrasonic Pest Repellent Devices to Affect Behavior of Bed Bugs (Hemiptera: Cimicidae),"  by K. M. Yturralde and R. W. Hofstetter,  Journal of Economic Entomology