摘要 |
A mobile device including a casing, a signal generator housed within the casing, for generating signals, at least one speaker housed within the casing and coupled with the signal generator, for producing sound from a signal generated by said signal generator, wherein the sound produced by the at least one speaker is (i) substantially inaudible, and (ii) vibrates the casing at a frequency approximately equal to a resonant frequency of the casing.
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