PhD Project

Short Summary

Worldwide there are 360 million people that suffer from severe to profound hearing loss (WHO, 2012). Hearing loss can considerably affect the quality of life of deaf individuals and can in some cases lead to social isolation or depression. Nowadays, many deaf individuals can benefit from receiving a cochlear implant. A cochlear implant (CI) is an electronic prosthetic device that bypasses the function of the damaged inner ear and enables individuals with severe sensorineural hearing loss to partially regain the ability to perceive speech. However, the improvement in speech perception is limited by the degraded speech signal that is received via the CI, which lacks spectro-temporal fine structure that is important for the perception of voice characteristics, such as fundamental frequency and vocal tract length. Fundamental frequency (F0) or 'pitch' is based on glottal pulse rate and vocal tract length (VTL) is determined by the size of the speaker, which influences the distribution of formant frequencies.

Voice characteristics provide essential information for the recognition of speakers and the perception of speech in noise or background speech. Previous research of the UMCG ENT department has shown that the impaired perception of voice characteristics leads to difficulties with the identification of the gender and emotions of speakers in adult CI users (Fuller et al., 2014; Gilbers et al., 2015).

While many CI users have good speech perception in silence, the perception of speech in noise or background speech, the so-called 'cocktail party problem' (Cherry, 1953), often remains difficult for even the most succesful CI users. Since speech perception usually takes place in noisy environments, the inability of CI users to distinguish speakers leads to less meaningful language exposure. This may contribute to the delayed language development and large individual variation in linguistic abilities that is often found in children with CIs (Szagun, 2001; Geers, Davidson, Uchanski, & Nicholas, 2013).