Тhe role of auditory feedback in voice control with normal and impaired hearing

Abstract

Control of speech fulfilled by cooperation between feedforward control and feedback control. Feedforward control activates program of articulation, whereas feedback control carries acoustic and sensorimotor information about pronounced utterance. Their complementary speech control function described by the DIVA model, which based on adjustment of auditory and proprioceptive signals relatively to program of articulation in nerve centers. The inconsistency between the sensory information received via feedback and the presentation of the acoustic signal in the auditory nucleus causes corrective commands. Auditory feedback is necessary for the correct development of children’s articulatory skills, i.e. forming feedforward control. For this reason, prelingually deafened adults have significant articulation impairments due to immature articulatory skills. In postlingual deafness, the previously forming feedforward control allows pronounce phonemes successfully. However, in people with sensorineural hearing loss, control of phonation and articulation through the auditory feedback deteriorates, which expressed by an increase of voice intensity, changes in the speech spectral characteristics and instability in frequency and amplitude. Similar speech changes are found in speakers with normal hearing in the presence of noise that masks the speaker’s voice (Lombard effect). In noise, voice intensity increase, spectral characteristics of speech shift to the high-frequency region, and increase the amplitude and speed of articulatory movements (hyperarticulation). This speech reorganization is an adaptation of the speaker’s own voice to background noise, which purpose is to unmask the speech and restore auditory feedback control.