Audio apparatus (30) comprising a piezoelectric transducer (44) and coupling means (54) for coupling the transducer to a user's pinna (32) whereby the transducer excites vibration in the pinna (32) to cause it to transmit an acoustic signal from the transducer (44) to a user's inner ear, characterised in that the transducer is embedded in a casing (42) of relatively soft material and the casing (42) is mounted to a housing (34) of relatively hard material such that a cavity (48) is defined between the casing (42) and housing (34). A method of designing audio apparatus comprising mechanically coupling a piezoelectric transducer to a user's pinna and driving the transducer so that the transducer excites vibration in the pinna to cause it to transmit an acoustic signal from the transducer to a user's inner ear, characterised by embedding the transducer in a casing of relatively soft material and by mounting the casing to protective housing of relatively hard material such that a cavity is defined between the casing and housing.