• Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Journal of the Acoustical Society of America

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

May 2011

Volume 129, Issue 5, pp. EL161-3425

Return to All Sections
back to top
RSS Feeds

Characterizing distortion-product otoacoustic emission components across four species

Glen K. Martin, Barden B. Stagner, You Sun Chung, and Brenda L. Lonsbury-Martin

J. Acoust. Soc. Am. Volume 129, Issue 5, pp. 3090-3103 (2011); (14 pages) | Cited 2 times

Online Publication Date: 10 May 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Distortion-product otoacoustic emissions (DPOAEs) were measured as level/phase (L/P) maps in humans, rabbits, chinchillas, and rats with and without an interference tone (IT) placed either near the 2f1−f2 DPOAE frequency place (fdp) or at one-third of an octave above the f2 primary tone (1/3-oct IT). Vector differences between with and without IT conditions were computed to derive a residual composed of the DPOAE components removed by the IT. In humans, a DPOAE component could be extracted with the expected steep phase gradient indicative of reflection emissions by ITs near fdp. In the laboratory species, ITs near fdp failed to produce any conclusive evidence for reflection components. For all species, 1/3-oct ITs extracted large DPOAE components presumably generated at or basal to the IT-frequency place that exhibited both distortion- and reflection-like phase properties. Together, these findings suggested that basal distortion components could assume reflection-like phase behavior when the assumptions of cochlear-scaling symmetry, the basis for shallow phase gradients for constant f2/f1 ratio sweeps, are violated. The present results contradict the common belief that DPOAE components associated with steep or shallow phase slopes are unique signatures for reflection emissions arising from fdp or distortion emissions generated near f2, respectively.
Show PACS
43.64.Bt Models and theories of the auditory system
43.64.Jb Otoacoustic emissions
43.64.Kc Cochlear mechanics

The breaking of cochlear scaling symmetry in human newborns and adults

Carolina Abdala, Sumitrajit Dhar, and Srikanta Mishra

J. Acoust. Soc. Am. Volume 129, Issue 5, pp. 3104-3114 (2011); (11 pages)

Online Publication Date: 10 May 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Scaling symmetry appears to be a fundamental property of the cochlea as evidenced by invariant distortion product otoacoustic emission (DPOAE) phase above ∼1–1.5 kHz when using frequency-scaled stimuli. Below this frequency demarcation, phase steepens. Cochlear scaling and its breaking have been described in the adult cochlea but have not been studied in newborns. It is not clear whether immaturities in cochlear mechanics exist at birth in the human neonate. In this study, DPOAE phase was recorded with a swept-tone protocol in three, octave-wide segments from 0.5 to 4 kHz. The lowest-frequency octave was targeted with increased signal averaging to enhance signal-to-noise ratio (SNR) and focus on the apical half of the newborn cochlea where breaks from scaling have been observed. The results show: (1) the ear canal DPOAE phase was dominated by the distortion-source component in the low frequencies; thus, the reflection component cannot explain the steeper slope of phase; (2) DPOAE phase-frequency functions from adults and infants showed an unambiguous discontinuity around 1.4 and 1 kHz when described using two- and three-segment fits, respectively, and (3) newborns had a significantly steeper slope of phase in the low-frequency portion of the function which may suggest residual immaturities in the apical half of the newborn cochlea.
Show PACS
43.64.Bt Models and theories of the auditory system
43.64.Kc Cochlear mechanics
43.64.Jb Otoacoustic emissions

Breaking away: Violation of distortion emission phase-frequency invariance at low frequencies

Sumitrajit Dhar, Abigail Rogers, and Carolina Abdala

J. Acoust. Soc. Am. Volume 129, Issue 5, pp. 3115-3122 (2011); (8 pages) | Cited 6 times

Online Publication Date: 10 May 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The phase versus frequency function of the distortion product otoacoustic emission (DPOAE) at 2f1 − f2 is approximately invariant at frequencies above 1.5 kHz in human subjects when recorded with a constant f2/f1. However, a secular break from this invariance has been observed at lower frequencies where the phase-gradient becomes markedly steeper. Apical DPOAEs, such as 2f1 − f2, are known to contain contributions from multiple sources. This experiment asked whether the phase behavior of the ear canal DPOAE at low frequencies is driven by the phase of the component from the distortion product (DP) region at 2f1 − f2, which exhibits rapid phase accumulation. Placing a suppressor tone close in the frequency to 2f1 − f2 reduced the contribution of this component to the ear canal DPOAE in normal-hearing adult human ears. When the contribution of this component was reduced, the phase behavior of the ear canal DPOAE was not altered, suggesting that the breaking from DPOAE phase invariance at low frequencies is an outcome of apical-basal differences in cochlear mechanics. The deviation from DPOAE phase invariance appears to be a manifestation of the breaking from approximate scaling symmetry in the human cochlear apex.
Show PACS
43.64.Bt Models and theories of the auditory system
43.64.Jb Otoacoustic emissions
43.64.Kc Cochlear mechanics

Level dependence of distortion product otoacoustic emission phase is attributed to component mixing

Carolina Abdala, Sumitrajit Dhar, and Radha Kalluri

J. Acoust. Soc. Am. Volume 129, Issue 5, pp. 3123-3133 (2011); (11 pages) | Cited 5 times

Online Publication Date: 10 May 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Distortion product otoacoustic emissions (DPOAEs) measured in the ear canal represent the vector sum of components produced at two regions of the basilar membrane by distinct cochlear mechanisms. In this study, the effect of stimulus level on the 2f1 − f2 DPOAE phase was evaluated in 22 adult subjects across a three-octave range. Level effects were examined for the mixed DPOAE signal measured in the ear canal and after unmixing components to assess level effects individually on the distortion (generated at the f1, f2 overlap) and reflection (at fdp) sources. Results show that ear canal DPOAE phase slope becomes steeper with decreasing level; however, component analysis further explicates this result, indicating that interference between DPOAE components (rather than a shift in mechanics related to distortion generation) drives the level dependence of DPOAE phase measured in the ear canal. The relative contribution from the reflection source increased with decreasing level, producing more component interference and, at times, a reflection-dominated response at the lowest stimulus levels. These results have implications for the use of DPOAE phase to study cochlear mechanics and for the potential application of DPOAE phase for clinical purposes.
Show PACS
43.64.Bt Models and theories of the auditory system
43.64.Kc Cochlear mechanics
43.64.Jb Otoacoustic emissions

Distribution of standing-wave errors in real-ear sound-level measurements

Susan A. Richmond, Judy G. Kopun, Stephen T. Neely, Hongyang Tan, and Michael P. Gorga

J. Acoust. Soc. Am. Volume 129, Issue 5, pp. 3134-3140 (2011); (7 pages) | Cited 3 times

Online Publication Date: 10 May 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Standing waves can cause measurement errors when sound-pressure level (SPL) measurements are performed in a closed ear canal, e.g., during probe-microphone system calibration for distortion-product otoacoustic emission (DPOAE) testing. Alternative calibration methods, such as forward-pressure level (FPL), minimize the influence of standing waves by calculating the forward-going sound waves separate from the reflections that cause errors. Previous research compared test performance (Burke et al., 2010) and threshold prediction (Rogers et al., 2010) using SPL and multiple FPL calibration conditions, and surprisingly found no significant improvements when using FPL relative to SPL, except at 8 kHz. The present study examined the calibration data collected by Burke et al. and Rogers et al. from 155 human subjects in order to describe the frequency location and magnitude of standing-wave pressure minima to see if these errors might explain trends in test performance. Results indicate that while individual results varied widely, pressure variability was larger around 4 kHz and smaller at 8 kHz, consistent with the dimensions of the adult ear canal. The present data suggest that standing-wave errors are not responsible for the historically poor (8 kHz) or good (4 kHz) performance of DPOAE measures at specific test frequencies.
Show PACS
43.64.Jb Otoacoustic emissions
43.58.Vb Calibration of acoustical devices and systems

Distortion products and backward-traveling waves in nonlinear active models of the cochlea

Renata Sisto, Arturo Moleti, Teresa Botti, Daniele Bertaccini, and Christopher A. Shera

J. Acoust. Soc. Am. Volume 129, Issue 5, pp. 3141-3152 (2011); (12 pages) | Cited 7 times

Online Publication Date: 10 May 2011

Full Text: Read Online (HTML) | Download PDF

Show Abstract
This study explores the phenomenology of distortion products in nonlinear cochlear models, predicting their amplitude and phase along the basilar membrane. The existence of a backward-traveling wave at the distortion-product frequency, which has been recently questioned by experiments measuring the phase of basilar-membrane vibration, is discussed. The effect of different modeling choices is analyzed, including feed-forward asymmetry, micromechanical roughness, and breaking of scaling symmetry. The experimentally observed negative slope of basilar-membrane phase is predicted by numerical simulations of nonlinear cochlear models under a wide range of parameters and modeling choices. In active models, positive phase slopes are predicted by the quasi-linear analytical computations and by the fully nonlinear numerical simulations only if the distortion-product sources are localized apical to the observation point and if the stapes reflectivity is unrealistically small. The results of this study predict a negative phase slope whenever the source is distributed over a reasonably wide cochlear region and/or a reasonably high stapes reflectivity is assumed. Therefore, the above-mentioned experiments do not contradict “classical” models of cochlear mechanics and of distortion-product generation.
Show PACS
43.64.Kc Cochlear mechanics
Return to All Sections
Close

Home Publications Meetings Contact ASA Site Map Back to Top

Copyright © Acoustical Society of America

close