Patients who suffer larynx and voice box deficiencies are typically unable to speak anything more than hoarse whispers without the aid of voice prostheses or rehabilitation techniques such as oesophageal speech. Speech therapists and researchers working in this field have, for many years, pursued the goal of rehabilitation of such patients so as to return to them the ability to speak in a natural sounding voice. Typically due to removal of, or damage to, the voice box in a surgical operation such as laryngectomy, the pitch generation mechanism within these patients voice production systems, is lacking. Without a source of excitation for voiced speech, only hoarse, whisper like and sometimes not easily perceptible sounds can be produced. This speech is obviously different to that from normal speakers, and will have lost many of the distinctive characteristics of the original speech. However, these patients typically retain the ability to whisper in a similar way to normal speakers
