Further assessment of forward pressure level for in situ calibration

Self Cite

A number of acoustical applications require the transformation of acoustical quantities, such as impedance and pressure that are measured at the entrance of the ear canal, to quantities at the eardrum. This transformation often requires knowledge of the shape of the ear canal. Previous attempts to measure ear-canal area functions were either invasive, non-reproducible, or could only measure the area function up to a point mid-way along the canal. A method to determine the area function of the ear canal from measurements of acoustic impedance at the entrance of the ear canal is described. The method is based on a solution to the inverse problem in which measurements of impedance are used to calculate reflectance, which is then used to determine the area function of the canal. The mean ear-canal area function determined using this method is similar to mean ear-canal area functions measured by other researchers using different techniques. The advantage of the proposed method over previous methods is that it is non- invasive, fast, and reproducible.

Section: Discussionmentioning

confidence: 83%

Section: Discussionmentioning

confidence: 99%

Inverse solution of ear-canal area function from reflectance

Rasetshwane

Neely

2011

Self Cite

“…To expedite the computation, s n was constrained to the interval [0,20] ms. 5 Analysis of the noise waveform is identical except that, rather than being varied, the value of the delay s n , and hence of the emission frequency, is fixed at the value determined from the emission waveform. 6 Because our principal aim was to compare the discrete and swept-tone paradigms, rather than obtain baseline SFOAE data at known stimulus levels, we made no attempt to compensate for uncertainties in the calibration arising from ear-canal standing waves (e.g., Scheperle et al, 2011). 7 Although we did not explore the possibility here, the time-frequency distance between the OAE and the suppressor may also influence the magnitude of olivocochlear efferent effects.…”

Section: Acknowledgmentsmentioning

confidence: 99%

Measuring stimulus-frequency otoacoustic emissions using swept tones

Kalluri

Shera

2013

Although stimulus-frequency otoacoustic emissions (SFOAEs) offer compelling advantages as noninvasive probes of cochlear function, they remain underutilized compared to other evoked emission types, such as distortion-products (DPOAEs), whose measurement methods are less complex and time-consuming. Motivated by similar advances in the measurement of DPOAEs, this paper develops and characterizes a more efficient SFOAE measurement paradigm based on swept tones. In contrast to standard SFOAE measurement methods, in which the emissions are measured in the sinusoidal steady-state using discrete tones of well defined frequency, the swept-tone method sweeps rapidly across frequency (typically at rates of 1 Hz/ms or greater) using a chirp-like stimulus. Measurements obtained using both swept-and discrete-tone methods in an interleaved suppression paradigm demonstrate that the two methods of measuring SFOAEs yield nearly equivalent results, the differences between them being comparable to the run-to-run variability encountered using either method alone. The match appears robust to variations in measurement parameters, such as sweep rate and direction. The near equivalence of the SFOAEs obtained using the two measurement methods enables the interpretation of swept-tone SFOAEs within existing theoretical frameworks. Furthermore, the data demonstrate that SFOAE phase-gradient delaysincluding their large and irregular fluctuations across frequency-reflect actual physical time delays at different frequencies, showing that the physical emission latency, not merely the phase gradient, is inherently irregular.

“…Calibrating the ear-canal sound in terms of absorbed sound power helped interpret a tip-to-tail level difference of the suppression tuning curve of SFOAEs at high frequencies (Keefe and Schairer, 2011). Scheperle et al (2011) described benefits of quantifying ear-canal sound level in terms of forward pressure rather than total pressure for clinical DPOAE measurements, and described technical improvements to measure L F up to 10 kHz. They raised the issue of whether middle-ear status should be taken into account when calibrating the ear-canal stimulus level, as the cochlea may not act as an ideal power detector.…”

Section: A Stimulus Control For Standing Wave Effectsmentioning

confidence: 99%

Comparing otoacoustic emissions evoked by chirp transients with constant absorbed sound power and constant incident pressure magnitude

Keefe

Feeney

Hunter

et al. 2017

Human ear-canal properties of transient acoustic stimuli are contrasted that utilize measured ear-canal pressures in conjunction with measured acoustic pressure reflectance and admittance. These data are referenced to the tip of a probe snugly inserted into the ear canal. Promising procedures to calibrate across frequency include stimuli with controlled levels of incident pressure magnitude, absorbed sound power, and forward pressure magnitude. An equivalent pressure at the eardrum is calculated from these measured data using a transmission-line model of ear-canal acoustics parameterized by acoustically estimated ear-canal area at the probe tip and length between the probe tip and eardrum. Chirp stimuli with constant incident pressure magnitude and constant absorbed sound power across frequency were generated to elicit transient-evoked otoacoustic emissions (TEOAEs), which were measured in normal-hearing adult ears from 0.7 to 8 kHz. TEOAE stimuli had similar peak-to-peak equivalent sound pressure levels across calibration conditions. Frequency-domain TEOAEs were compared using signal level, signal-to-noise ratio (SNR), coherence synchrony modulus (CSM), group delay, and group spread. Time-domain TEOAEs were compared using SNR, CSM, instantaneous frequency and instantaneous bandwidth. Stimuli with constant incident pressure magnitude or constant absorbed sound power across frequency produce generally similar TEOAEs up to 8 kHz.