The influence of linguistic skills on speech understanding in noise

People with hearing impairment suffer from a reduced ability to understand
speech in daily life situations, especially in noisy environments. Hearing
impairment therefore is known to have a considerable psychosocial impact. A
person*s abilities to understand speech in noise depend on auditory, cognitive
and linguistic skills (George et al. 2007;Zekveld et al. 2007;Rönnberg et al.
2008). The current study is part of the research program of the ENT/audiology
department which aims to enhance the social participation of hearing impaired
people despite their hearing loss. The specific contribution of this study is
to examine the influence of linguistic skills on speech intelligibility in
noise. Congenital hearing loss is a chronic condition. A major risk factor is
impaired development of linguistic skills. This will be studied in part one of
the present project. The outcomes will have implications for rehabilitation of
congenitally hearing impaired listeners. This hearing-impairment-induced
reduction of linguistic skills will in its turn reduce the compensatory
resources of the hearing impaired to understand speech in everyday noisy
surroundings. This is studied in the second part. Outcomes of this part will
also have implications for the multidisciplinary rehabilitation program for
hearing impaired patients. Especially they may add focus to the rehabilitation
program: knowing what part of reduced speech intelligibility scores is due to
auditory factors sets the goals for auditory rehabilitation more precisely. The
obtained information will enable us to further unravel the question which
factors affect speech recognition.

The primary objective of this study is to examine the role of linguistic skills
in speech understanding. To reach this objective, we will first identify those
features of the Dutch language which are affected by congenital hearing
impairment.

The first part of the project is an explorative study of the effect of
congenital hearing loss on linguistic skills. People with a congenital hearing
impairment acquire language with inferior auditory input during the critical
period for acquiring language (Lenneberg 1967;Singleton and Ryan 2004) and
further on. The development of the linguistic system can suffer from this
reduced and often distorted input. By performing analyses of spontaneous
language of (young) adults with a moderate to severe congenital hearing
impairment (MCHI and SCHI) we will identify the features of the Dutch language
which are most vulnerable to be affected by hearing impairment. Language
samples of normally hearing people (NH) and of adults with presbyacusis (P),
i.e. hearing loss with onset after the critical period, will be analysed to
compare their linguistic performance with the congenitally hearing impaired.
In the second part of the study, we will examine the impact of linguistic
skills on speech recognition abilities. As much as is possible, the obtained
results from the first part of the study, i.e. the information concerning the
aspects of language which were affected by congenital hearing impairment, will
be incorporated in the second part. A distortion-sensitivity approach will be
used: speech intelligibility will be measured with sentence material in which
linguistic information is distorted. Visual and auditory speech recognition
tests will be performed. The results of these tests will point out to what
extent the performances of the different groups (MCHI, SCHI, NH and P) are
affected by linguistic distortion and to what extent these linguistic skills
are used in the process of speech understanding in noise. The differences found
with the distortion-sensitivity approach are assumed to reflect the underlying
differences in linguistic proficiency between subjects.

Participants will be invited to attend three test sessions with a mean duration
of two hours each. There are no risks connected to participation in this
research. The burden for the individual participant is low.