Abstract: A contact sensitive device includes a member capable of supporting bending waves and a plurality of sensors mounted on the member for measuring bending wave vibration in the member. The sensors measure the bending wave signals and by calculating a phase angle for each measured bending wave signal and a phase difference between the phase angles of least two pairs of sensors so that at least two phase differences are calculated, the location of the contact can be determined.

Abstract: Active acoustic device comprises a panel member (11) having distribution of resonant modes of bending wave action determining acoustic performance in conjunction with a transducer (31-34). The transducer (31-34) is coupled to the panel member (11) at a marginal position. The arrangement is such as to result in acoustically acceptable action dependent on said distribution of active said resonant modes. Methods of selecting the transducer location, or improvement by location of localized marginal clamping, rely on assessing best or better operative interaction of said transducer (31-34) and the panel members (11) according to parameters of acoustic output for the device as an acoustic radiator.

Abstract: A loudspeaker comprising a panel-form acoustic member adapted for operation as a bending wave radiator and an electrodynamic moving coil transducer having a voice coil mounted to the acoustic member to excite bending wave vibration in the acoustic member. The junction between the voice coil and the acoustic member is of sufficient length in relation to the size of the acoustic member to represent a line drive such that the acoustic member has a mechanical impedance which has a rising trend with bending wave frequency.