Normal intelligibility functions for the Auditec CID W-22 test at 30% and 60% time-compression

Time-compressed speech has been used to identify the site of central auditory disorders and auditory processing problems. Some authors suggest that the determination of audiometric normalcy should include satisfactory performance on a speech intelligibility test sensitive to central auditory dysfunction, such as time-compressed speech. Before scores from patients with auditory disorders can be meaningfully interpreted, however, it is necessary to establish normal performance on standardized recordings. Thus, this study was undertaken to generate speech intelligibility functions in a normal-hearing population using the Auditec CID W-22 recordings with 30% and 60% time-compression. The 30% condition revealed a slope of 3.24% per decibel and the function approached a plateau at 35 dB sensation level (SL). The 60% condition produced a function that increased gradually at 1.8% per decibel over the 20 to 80% intelligibility range. An intelligibility score of 82% was observed at 46 dB SL where the function approached an asymptote. These functions provide a standard against which subjects with central auditory dysfunctions can be compared. The relative difficulty that normal subjects had with the 60% time-compressed speech suggests that this condition may be too difficult for some subjects with central auditory disorders.