The development of a dual-modality hearing prosthesis is described that utilizes vibrotactile stimulation of the ear for /s/ and /z/ phoneme sounds of speech and amplified acoustic stimulation for other sounds that fall within the usable range of the impaired ear. The work has focussed on the development of a method for detection of the /s/ and /z/ phonemes from the acoustic signal under natural conditions of conversational speech and on an efficient implementation of a piezoelectric vibrotactile transducer that can be incorporated into an ear-level module.