Measuring human cochlear traveling wave delay using distortion product emission phase responses

Area of Science:

• Auditory Neuroscience
• Otoacoustic Emissions
• Human Physiology

Background:

• Cochlear traveling wave delays are crucial for auditory perception.
• Previous estimation methods, like electrocochleography, can be invasive or time-consuming.
• A noninvasive, purely cochlear-based method is needed for accurate delay measurements.

Purpose of the Study:

• To present and validate a novel method for estimating cochlear traveling wave delays.
• To assess the reliability and characteristics of these delay estimates.
• To compare delay differences between sexes and within/between subjects.

Main Methods:

• Distortion product emission (DPE) phase responses were measured in 36 human ears (18 male, 18 female) with normal hearing.
• DPE phase responses were analyzed across eight frequencies (f2) from 0.78 to 10 kHz.
• Traveling wave delays were calculated based on the assumption of DPE generation at the f2 place.

Main Results:

• Linear relationships were observed between DPE phase and DPE frequency.
• Estimated traveling wave delays ranged from 1 ms (10 kHz) to 3.5 ms (0.78 kHz), aligning with prior electrocochleography data.
• Test-retest reliability was within 0.25 ms, and within-subject interaural differences were typically under 0.5 ms.
• Male ears showed significantly longer delays (8%) at 0.78 kHz compared to female ears.

Conclusions:

• Distortion product emission phase responses provide a reliable, rapid, and noninvasive estimation of cochlear traveling wave delays.
• This DPE-based method offers advantages over existing electrophysiological and psychophysical techniques.
• The study highlights sex-based differences in cochlear delay, particularly at lower frequencies.