DPOAE Responses in Humans and Ear Models: Can a Single-Loudspeaker Approach Match the Two-Loudspeaker Technique?
When a dual-tone frequency stimulus (<inline-formula> <tex-math notation="LaTeX">$f_{1}$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$f_{2}$ </tex-math></inline-formula>) is presented to the ear, the...
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| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
IEEE
2025-01-01
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| Series: | IEEE Access |
| Subjects: | |
| Online Access: | https://ieeexplore.ieee.org/document/11036177/ |
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| Summary: | When a dual-tone frequency stimulus (<inline-formula> <tex-math notation="LaTeX">$f_{1}$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$f_{2}$ </tex-math></inline-formula>) is presented to the ear, the cochlea responds by generating a tone at <inline-formula> <tex-math notation="LaTeX">$2 f_{1}-f_{2}$ </tex-math></inline-formula>, known as the distortion product otoacoustic emission (DPOAE), useful for assessing cochlear health. Typically, to measure emissions from one ear, tones at <inline-formula> <tex-math notation="LaTeX">$f_{1}$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$f_{2}$ </tex-math></inline-formula> are generated by two separate loudspeakers and delivered through tubing to a single probe in most clinical DPOAE devices. Using a single loudspeaker, however, introduces cubic intermodulation distortion (IMD) at <inline-formula> <tex-math notation="LaTeX">$2 f_{1}-f_{2}$ </tex-math></inline-formula>, which interferes with the DPOAE signal, making accurate measurements difficult. In this study, to enable DPOAE measurement using only one loudspeaker, we designed a three-tone stimulus. The third tone was adjusted in phase and amplitude to destructively interfere with the IMD at <inline-formula> <tex-math notation="LaTeX">$2 f_{1}-f_{2}$ </tex-math></inline-formula>, effectively canceling it. Using an IEC 60318–4 ear simulator, we optimized the third tone parameters and then measured DPOAEs with single- and two-loudspeaker setups. DPOAEs from 54 ears were measured at frequencies from 1–8 kHz using an ER-10B+ DPOAE microphone system, with an <inline-formula> <tex-math notation="LaTeX">$f_{2}/f_{1}$ </tex-math></inline-formula> ratio of 1.22 and stimulus levels of <inline-formula> <tex-math notation="LaTeX">$65/55$ </tex-math></inline-formula> dB SPL (<inline-formula> <tex-math notation="LaTeX">$L_{1}/L_{2}$ </tex-math></inline-formula>). Bland-Altman analysis, with limits of agreement (LoA), was performed to assess whether the method sufficiently agreed with the standard DPOAE technique. Additionally, 10 silicone ear models, created from 3D scans of real human outer ears, were used to evaluate residual IMD that cannot be measured in humans due to the presence of DPOAEs. These models accounted for the anatomical effects of the ear canal shape, providing an objective, realistic assessment of cancellation performance. |
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| ISSN: | 2169-3536 |