I'd guess it is a fairly common (but fairly unknown) phenomenon, that sound frequencies just above your audible range can be *felt*. I can (unreliably) *feel* sound in the 19-20kHz range, and *reliably* hear a TV (PAL uses 25 fps, 625 lines/image, which gives a frequency of 15.6 kHz). Certain TV cameras (e.g. surveillance cameras) are audible, too. I'd bet that your'e going to find up one of those in the mall.