The microstructure of auditory sensitivity in the audiometric frequencies

This research was designed to provide new information regarding the cochlear sensitivities that occur in the octave intervals for the audiometric frequencies between 250-8000 Hz. Common clinical procedures in audiology utilize behavioral testing with pure tones at the octave frequencies between 250-8000 Hz. In many clinical assessments the speech discrimination performance of patients is poorer than would be expected from the pure tone results. Recent electrophysiological studies have shown “dead regions” of the cochlea across the entire audibility range. Both speech discrimination performance and “dead regions” may be related to variations in audiometric thresholds between standard audiometric test frequencies. We are now able to generate calibrated tonal signals at various frequencies between octaves. We have selected 24 logarithmically spaced frequencies between octaves for a total of 121 discrete frequencies between 250 and 8000 Hz. These tonal signals were presented to listeners with various types of hearing loss. A computer controlled the presentation of signals and a button press by the patient recorded the response. Based upon the patient response a testing algorithm was designed to minimize the test time. The pattern of this threshold audiogram and clinical implications will be discussed