“…Vibrations carry rich information of locations [8-10, 12, 17], identifications [4,26,57,57,62], gestures [5-7, 14-16, 28, 67], activities [11,13,33], speech [26], materials [3,46], weights [69] and so on for sensing technology. Kunze et al [37] and Cho et al [18] find the location of a mobile phone by measuring acceleration (and also sound [37]) using internal sensors after imposing a vibration. Such hand-transmitted vibrations are generated and measured by surface transducers and contact microphones.…”