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Acoustic reflex measures at high probe frequency: a phasor diagram approach
1Department of Logopaedics (Audiology Section), University of Cape Town, South Africa.
British Journal of Audiology
|June 1, 1995
Summary
High-frequency acoustic reflex measurements confirm that the acoustic reflex primarily affects stiffness, not resistance, in most normal ears. This finding aligns with previous low-frequency studies, suggesting consistent reflex mechanisms across frequencies.
Area of Science:
- Audiology
- Otoacoustic Emissions
- Biomedical Engineering
Background:
- Acoustic reflex measurements at high probe frequencies are not well-documented.
- Existing studies on low-frequency acoustic reflexes show conflicting results regarding impedance changes, though increased stiffness is consistently observed.
Purpose of the Study:
- To investigate the effect of the acoustic reflex on middle ear impedance at a high probe frequency (1000 Hz).
- To determine if the acoustic reflex's effect on impedance is consistent between low and high probe frequencies.
Main Methods:
- Utilized phasor diagrams to analyze probe tip susceptance and conductance in 30 normal ears at a 1000 Hz probe frequency.
- Qualitatively analyzed phasor diagrams for three different stimuli.
Main Results:
- 82% of the 90 analyzed phasor diagrams matched a constant-resistance stiffness-change model.
- The acoustic reflex primarily altered stiffness, consistent with findings at lower probe frequencies.
- This effect was observed in stiffness-dominated or naturally resonant ears at 1000 Hz.
Conclusions:
- The acoustic reflex appears to have a consistent effect on middle ear stiffness across both low and high probe frequencies in most cases.
- Further research is needed to clarify the reflex's effect on mass-dominated systems at high frequencies.