An Extended BKB Sentence Test Appropriate for a Wide Range of Speech Perception Abilities

Abstract

Near zero percent performance has been reported for some users of the Bench-Kowal-Bamford (BKB) sentence test. The test is commonly used in the United Kingdom for hearing impaired listeners over eight years old to assess an individual’s speech recognition ability, and in particular is used with cochlear implant users. The sentences contain simple and natural vocabulary that are suitable for almost any age range. The main aim of this thesis was to generate a range of easier BKB sentences that are more appropriate for listeners who achieve these low scores with the standard BKB test. A range of tests were developed, these include: the Easy BKB Sentence Test, the Repeated and Emphasised BKB Sentences and the Closed Set BKB Sentence Test. When presented to either cochlear implant listeners or normally hearing adults in background noise, all of the easier tests were significantly more intelligible than the standard BKB sentence test. The sentences were also presented to normally hearing children between the ages of four and eight, and although there was no significant difference between the easier and original sentences, it was identified that children over five years of age achieve high scores. The second aim of this thesis was to greatly increase the number of sentences within the BKB sentence test to reduce the learning effect that can be encountered when using the test repeatedly. The new sentences maintained the characteristics of the original BKB sentences, and a total of 1664 new sentences were recorded alongside the original 336 BKB sentences. No significant differences between the new and original sentences were found. Thus, enabling 2000 BKB+collective sentences to be formed. The two aims of the thesis were achieved, and an extensive collection of BKB sentence tests have been developed for clinical use.