Prosodic boundaries in alaryngeal speech

Alaryngeal speakers (speakers in whom the larynx has been removed) have inconsistent control over acoustic parameters such as F(0) and duration. This study investigated whether proficient tracheoesophageal and oesophageal speakers consistently convey phrase boundaries. It was further investigated if these alaryngeal speakers used the same hierarchy of acoustic boundary cues that is found in normal speakers. A perception experiment revealed that listeners identified prosodic boundaries less accurately in oesophageal speakers. Acoustic analyses showed that laryngeal speakers used pre-boundary lengthening and pitch movements at phrase boundaries, as expected. Tracheoesophageal speakers used pre-boundary-lengthening and pauses and oesophageal speakers used pauses to convey phrase boundaries. Two oesophageal speakers also paused inappropriately, within phrases. Although these two speakers differentiated between air-injection and prosodic pauses, listeners were unable to tell the two types of pauses apart. Alaryngeal speakers might benefit from therapy that specifically teaches them how to optimize their prosodic abilities.