| dc.description.abstract |
It is generally accepted that persons with sensori-neural hearing losses have a narrower dynamic range than persons with normal hearing. This narrow dynamic range could be caused by elevated thresholds, or a combination of elevated thresholds and lowered loudness discomfort levels (LDL's). Which of these two possibilities actually takes place is still a question.It has been accepted by many audiologists that the narrow dynamic range is due to the combination of lowered LDL's and elevated thresholds (Fowler, 1963 and Eby and Williams, 1951). Recently some investigators have found results that conflict with the accepted reasons for the narrow dynamic range. They found similar LDL's in normal hearers and persons with sensori-neural losses. In these persons the narrow dynamic range appears to be due solely to the elevated thresholds.It is important to know the LDL's of individuals so that their residual hearing can be used to maximum. By simply knowing a person's threshold, it is not possible to predict how he will function auditorally when signals are presented above that threshold. A complete picture of auditory ability is needed to determine how a person might function auditorally.When selecting a hearing aid for a person* knowledge of the LDL is important. Hearing aids that can give all the amplification that one will ever need are available. How much amplification a person can use varies among individuals. In the adult or older child no problem exists in determining the maximum amount of amplification that can be used, These persons can tell when sounds are too loud. An infant or young child can not verbalize this. Therefore, if general rules about LDL's can be developed in different kinds of deafness, amplification can be planned for these persons.If it is found that LDL's for some sensori-neural ears are the same as or greater than normal hearers, such a finding requires explanation. It seems that some sensori-neural impairments are accompanied by "overrecruitment". In some of the previous studies where LDL's were found to be more like those of normal hearers recruitment appeared to be non-existent. Perhaps the time of onset of the loss has some bearing on the problem of overrecruitment. Perhaps, also, the site of the lesion and extent of damage determine this. Either of these assumptions could hold the answer as to why recruitment is or is not present. |
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