Purpose: This article describes patterns of speech modifications produced by talkers as a function of the degree of hearing impairment of communication partners during naturalistic conversations in noise. An explanation of observed speech modifications is proposed in terms of a generalization of the concept of effort. This account complements existing theories of listening effort by extending the concept of effort to the domain of interactive communication. Method: Twenty young adult normal hearing participants and 20 older adult hearing-impaired participants were tested in pairs. Each pair consisted of 1 young normal hearing participant and 1 older hearing-impaired participant. Pairs of participants took part in naturalistic conversations through the use of a referential communication task. Each pair completed a 5-min conversation in each of 5 different realistic acoustic environments. Results: Talkers modified their speech, in terms of level and spectrum, in a gradient manner reflecting both the acoustic environment and the degree of hearing impairment of their conversation partner. All pairs of participants were able to maintain communication across all acoustic environments regardless of degree of hearing impairment and the level of environmental noise. Contrasting effects of noise and hearing impairment on speech production revealed distinct patterns of speech modifications produced by normal hearing and hearing-impaired talkers during conversation. This may reflect the fact that only the speech modifications produced by normal hearing talkers functioned to compensate for the hearing impairment of a conversation partner. Conclusions: The data presented support the concept of communication effort as a dynamic feedback system between conversation participants. Additionally, these results provide insight into the nature of realistic speech signals, which are encountered by people with hearing impairment in everyday communication scenarios.
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