In the study of auditory prostheses, the Speech
Recognition Threshold (SRT) is the Signal to Noise Ratio (SNR)
at which 50% of words are correctly identified. SRT is typically
measured using an adaptive procedure wherein speech is
presented at a fixed sound pressure level (SPL) and the noise
level is varied according to the subject’s responses.
A roving level SRT test has been used by researchers with
the goal of including the effectiveness of Automatic Gain
Control (AGC) systems in SRT measurements. The roving
method presents speech at three different SPLs with the level
for each sentence chosen pseudo-randomly, while adaptively
varying the SNR.
This study used simulations to compare roving and fixed
level SRT tests. It was found that roving level tests have
significantly increased variability when there are leveldependent
differences in subject scores. The interleaved level
test is recommended as an alternative as it provides clear
visibility of level-dependent performance and a better
understanding of overall subject performance.