Level-dependent IMD cancellation for single-transducer DPOAE measurement using a lookup-table method

Area of Science:

• Audiology
• Bioacoustics
• Otoacoustic Emissions

Background:

• Distortion product otoacoustic emissions (DPOAEs) assess cochlear function using two primary tones.
• Conventional DPOAE measurement uses two sound sources to avoid transducer-generated distortion.
• Single-transducer systems are challenging due to intermodulation distortion (IMD) mimicking DPOAEs.

Purpose of the Study:

• To develop a method for accurate DPOAE measurement using a single transducer.
• To overcome the limitations of transducer nonlinearity in DPOAE assessment.
• To enable simpler and potentially more cost-effective DPOAE measurements.

Main Methods:

• A cancellation tone at the DPOAE frequency (f3) was introduced.
• A lock-in amplifier technique tuned the cancellation tone's amplitude and phase.
• A level-specific lookup table (LUT) managed IMD variations due to ear-canal acoustics.

Main Results:

• The method successfully reduced IMD at the DPOAE frequency.
• Single-transducer DPOAE measurements were enabled, overcoming previous limitations.
• Validation on 40 ears confirmed the method's efficacy against a two-transducer baseline.

Conclusions:

• A novel single-transducer DPOAE measurement technique was successfully developed.
• The use of a cancellation tone and LUT effectively mitigates IMD.
• This approach simplifies DPOAE assessment and holds potential for clinical application.