Speech discrimination functions for normal-hearing subjects with AB isophonemic word lists

This paper presents normal speech discrimination curves for both children and adults achieved with Arthur Boothroyd's isophonemic word lists--Southampton recording. 7 groups of normally hearing people, 15 subjects in each group, were tested. One of these groups consisted of adults with a mean age of 28.3 years (range 24-36 years) while the remaining six groups consisted of children, the youngest group being 6-years-olds and the oldest 11-year olds. Testing was carried out in a quiet environment using a close circuit arrangement consisting of the taped material presented to each subject via TDH-39 earphones. The mean discrimination scores obtained exhibited good test-retest reliability and the resulting discrimination curves showed the following characteristics: Curve gradient (10-90% discrimination score) varying from 4.2% per dB for 6-year-olds to 5.1% per dB for adults. The Half-Peak Level(HPL) varied from 32 dB for the adults to 37 dB for the 6-year-olds (the dB values relate to the dial readings on the speech audiometer employed).