Modules
Swept OAEs: SwDPOAE & SwSFOAE
SwOAEs
SwOAE measurements are a next-generation method for measuring otoacoustic emissions. Rather than transient clicks/chirps or tonal stimuli as used in TEOAE, DPOAE, and SFOAE measurements, SwOAE measurements use tonal sweeps.
The sweeps go from low-to-high or high-to-low frequencies over a few seconds. The sweeps are repeated, and signal-averaging is used to improve the signal-to-noise ratio. The averaged waveform is analyzed using a least-squares fit (LSF) or wavelet analysis based on a model of the human hearing system, rather than an FFT.
From the same measurement, the OAE response may be analyzed using different bandwidths to accentuate or smooth fine structure. OAE levels with arbitrary frequency resolution may be measured.
TEOAE, SFOAE, and DPOAE measurements all have limitations that reduce their clinical efficacy. Getting sufficient frequency resolution with SFOAE and DPOAE can take too long. It can take too long to get sufficient SNR with TEOAE. TEOAEs are also limited in their ability to reach higher frequencies. TEOAEs and SFOAEs are primarily reflection-source OAEs, but DPOAEs are a mix of distortion-source and reflection-source OAEs. There is no pure measure of distortion-source OAEs. SwOAE methods address many of the limitations of these earlier OAE methods.
Developed in collaboration with Dr Chris Shera, this module is currently research-only.
Types of SwOAE
SwDPOAE
Two sweeps are output with a specific frequency ratio and range. Sweeps can be configured for linear or log sweep rate, rate, and direction. The 2F1-F2 DPOAE is extracted using a LSF fit. Data files may be exported for extensive post hoc analysis, including unmixing the distortion and reflection source OAEs.
SwSFOAE
Sweeps (the stimulus sweep and the suppressor sweep) are output with a specific frequency ratio and range, in an ensemble of three or four. Sweeps can be configured for linear or log sweep rate, rate, and direction. The SFOAE is extracted using a LSF fit. Data files may be exported for extensive post hoc analysis. SwSFOAE is a more difficult measurement to make than SwDPOAE, as it requires stimulus stability across the 3-4 presentations, and the measurement takes longer. However, it provides a measure of the reflection component OAE with high frequency resolution.
Calibration
Standard and forward pressure level calibration may be selected.
Noise rejection
Two noise rejection schemas are provided for SwOAEs in OtoStat: standard and weighted. Unlike other OAEs, SwOAEs vary in time and frequency, and noise contamination may affect only specific frequencies at certain times. It is inefficient to reject a noisy sweep if only part of it is affected.
The recommended approach is “weighted,” where no waveform is rejected. Instead, Bayesian weighting is used. This is a common statistical method to reduce noise for the detection of signals. The variance of the noise is used to weight each frame. Data blocks with high noise variance are down-weighted, and those with low noise variance are up-weighted.
SwOAE on OtoStat
To run OtoStat+SwDPOAE or OtoStat_SwSFOAE you need a monaural or binaural OtoStat with the SwDPOAE and/or SwSFOAE Measurement Modules.
- Measure swept distortion-product and stimulus-frequency otoacoustic emissions.
- Preset measurement protocols included.
- Save your favorite protocols by name.
- Multiple views during real time data collection and in data review.
- In-the-ear probe calibration using standard or FPL calibration.
- Stopping rules terminate the test early once measurement quality is achieved.
- Detailed results export provides extensive data for offline analysis.