Hearing thresholds for speech using insert earphones versus supra-aural earphones.

Speech recognition thresholds (SRT) have been determined in two groups of subjects, one with normal hearing and one with various types and degrees of hearing loss. One ear was tested on each subject, using spondees as test-words, with Telephonics TDH-39 supraural earphones and EARTONE 3-A insert earphones. The mean difference in SRT using the two transducers was 1 dB and not statistically significant. No difference was seen between the two groups of subjects. We conclude that the two transducers, in spite of measurable differences in frequency response, are interchangeable. If an exact calibration of the insert earphone is to be made, the equipment should be adjusted to produce 1 dB lower test levels for the insert earphone than for the TDH-39 in standardized calibration set-ups.