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Wen H, Meaud J. Link between stimulus otoacoustic emissions fine structure peaks and standing wave resonances in a cochlear model. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2022; 151:1875. [PMID: 35364913 PMCID: PMC8934193 DOI: 10.1121/10.0009839] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 03/03/2022] [Accepted: 03/04/2022] [Indexed: 06/14/2023]
Abstract
In response to an external stimulus, the cochlea emits sounds, called stimulus frequency otoacoustic emissions (SFOAEs), at the stimulus frequency. In this article, a three-dimensional computational model of the gerbil cochlea is used to simulate SFOAEs and clarify their generation mechanisms and characteristics. This model includes electromechanical feedback from outer hair cells (OHCs) and cochlear roughness due to spatially random inhomogeneities in the OHC properties. As in the experiments, SFOAE simulations are characterized by a quasiperiodic fine structure and a fast varying phase. Increasing the sound pressure level broadens the peaks and decreases the phase-gradient delay of SFOAEs. A state-space formulation of the model provides a theoretical framework to analyze the link between the fine structure and global modes of the cochlea, which arise as a result of standing wave resonances. The SFOAE fine structure peaks correspond to weakly damped resonant modes because they are observed at the frequencies of nearly unstable modes of the model. Variations of the model parameters that affect the reflection mechanism show that the magnitude and sharpness of the tuning of these peaks are correlated with the modal damping ratio of the nearly unstable modes. The analysis of the model predictions demonstrates that SFOAEs originate from the peak of the traveling wave.
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Affiliation(s)
- Haiqi Wen
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, 771 Ferst Drive, Atlanta, Georgia 30332, USA
| | - Julien Meaud
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, 771 Ferst Drive, Atlanta, Georgia 30332, USA
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Altoè A, Charaziak KK, Dewey JB, Moleti A, Sisto R, Oghalai JS, Shera CA. The Elusive Cochlear Filter: Wave Origin of Cochlear Cross-Frequency Masking. J Assoc Res Otolaryngol 2021; 22:623-640. [PMID: 34677710 DOI: 10.1007/s10162-021-00814-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Accepted: 08/23/2021] [Indexed: 11/28/2022] Open
Abstract
The mammalian cochlea achieves its remarkable sensitivity, frequency selectivity, and dynamic range by spatially segregating the different frequency components of sound via nonlinear processes that remain only partially understood. As a consequence of the wave-based nature of cochlear processing, the different frequency components of complex sounds interact spatially and nonlinearly, mutually suppressing one another as they propagate. Because understanding nonlinear wave interactions and their effects on hearing appears to require mathematically complex or computationally intensive models, theories of hearing that do not deal specifically with cochlear mechanics have often neglected the spatial nature of suppression phenomena. Here we describe a simple framework consisting of a nonlinear traveling-wave model whose spatial response properties can be estimated from basilar-membrane (BM) transfer functions. Without invoking jazzy details of organ-of-Corti mechanics, the model accounts well for the peculiar frequency-dependence of suppression found in two-tone suppression experiments. In particular, our analysis shows that near the peak of the traveling wave, the amplitude of the BM response depends primarily on the nonlinear properties of the traveling wave in more basal (high-frequency) regions. The proposed framework provides perhaps the simplest representation of cochlear signal processing that accounts for the spatially distributed effects of nonlinear wave propagation. Shifting the perspective from local filters to non-local, spatially distributed processes not only elucidates the character of cochlear signal processing, but also has important consequences for interpreting psychophysical experiments.
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Affiliation(s)
- Alessandro Altoè
- Caruso Department of Otolaryngology Head & Neck Surgery, University of Southern California, CA, Los Angeles, USA.
| | - Karolina K Charaziak
- Caruso Department of Otolaryngology Head & Neck Surgery, University of Southern California, CA, Los Angeles, USA
| | - James B Dewey
- Caruso Department of Otolaryngology Head & Neck Surgery, University of Southern California, CA, Los Angeles, USA
| | - Arturo Moleti
- Department of Physics, University of Roma Tor Vergata, Rome, Italy
| | - Renata Sisto
- DIMEILA, INAIL, Monte Porzio Catone, Rome, Italy
| | - John S Oghalai
- Caruso Department of Otolaryngology Head & Neck Surgery, University of Southern California, CA, Los Angeles, USA
| | - Christopher A Shera
- Caruso Department of Otolaryngology Head & Neck Surgery, University of Southern California, CA, Los Angeles, USA.,Department of Physics and Astronomy, University of Southern California, Los Angeles, CA, USA
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Liu TC, Liu YW, Wu HT. Denoising click-evoked otoacoustic emission signals by optimal shrinkage. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2021; 149:2659. [PMID: 33940909 DOI: 10.1121/10.0004264] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Accepted: 03/24/2021] [Indexed: 06/12/2023]
Abstract
Click-evoked otoacoustic emissions (CEOAEs) are clinically used as an objective way to infer whether cochlear functions are normal. However, because the sound pressure level of CEOAEs is typically much lower than the background noise, it usually takes hundreds, if not thousands, of repetitions to estimate the signal with sufficient accuracy. In this paper, we propose to improve the signal-to-noise ratio (SNR) of CEOAE signals within limited measurement time by optimal shrinkage (OS) in two different settings: covariance-based optimal shrinkage (cOS) and singular value decomposition-based optimal shrinkage (sOS). By simulation, the cOS consistently enhanced the SNR by 1-2 dB from a baseline method that is based on calculating the median. In real data, however, the cOS cannot enhance the SNR over 1 dB. The sOS achieved a SNR enhancement of 2-3 dB in simulation and demonstrated capability to enhance the SNR in real recordings. In addition, the level of enhancement increases as the baseline SNR decreases. An appealing property of OS is that it produces an estimate of all single trials. This property makes it possible to investigate CEOAE dynamics across a longer period of time when the cochlear conditions are not strictly stationary.
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Affiliation(s)
- Tzu-Chi Liu
- Department of Electrical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Yi-Wen Liu
- Department of Electrical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
| | - Hau-Tieng Wu
- Department of Mathematics and Department of Statistical Science, Duke University, Durham, North Carolina 27708, USA
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Vencovský V, Vetešník A, Gummer AW. Nonlinear reflection as a cause of the short-latency component in stimulus-frequency otoacoustic emissions simulated by the methods of compression and suppression. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2020; 147:3992. [PMID: 32611132 DOI: 10.1121/10.0001394] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 05/22/2020] [Indexed: 06/11/2023]
Abstract
Stimulus-frequency otoacoustic emissions (SFOAEs) are generated by coherent reflection of forward traveling waves by perturbations along the basilar membrane. The strongest wavelets are backscattered near the place where the traveling wave reaches its maximal amplitude (tonotopic place). Therefore, the SFOAE group delay might be expected to be twice the group delay estimated in the cochlear filters. However, experimental data have yielded steady-state SFOAE components with near-zero latency. A cochlear model is used to show that short-latency SFOAE components can be generated due to nonlinear reflection of the compressor or suppressor tones used in SFOAE measurements. The simulations indicate that suppressors produce more pronounced short-latency components than compressors. The existence of nonlinear reflection components due to suppressors can also explain why SFOAEs can still be detected when suppressors are presented more than half an octave above the probe-tone frequency. Simulations of the SFOAE suppression tuning curves showed that phase changes in the SFOAE residual as the suppressor frequency increases are mostly determined by phase changes of the nonlinear reflection component.
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Affiliation(s)
- Václav Vencovský
- Department of Radioelectronics, Czech Technical University in Prague, Technická 2, 166 27 Prague, Czech Republic
| | - Aleš Vetešník
- Department of Nuclear Chemistry, Czech Technical University in Prague, Břehová 7, 115 19 Prague, Czech Republic
| | - Anthony W Gummer
- Department of Otolaryngology, Section of Physiological Acoustics and Communication, Eberhard-Karls-University Tübingen, Elfriede-Aulhorn-Strasse 5, 72076 Tübingen, Germany
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Wu HT, Liu YW. Analyzing transient-evoked otoacoustic emissions by concentration of frequency and time. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2018; 144:448. [PMID: 30075682 DOI: 10.1121/1.5047749] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Accepted: 07/06/2018] [Indexed: 06/08/2023]
Abstract
The linear part of transient evoked otoacoustic emission (TEOAE) is thought to be generated via coherent reflection near the characteristic place of constituent wave components. Because of the tonotopic organization of the cochlea, high frequency emissions return earlier than low frequencies; however, due to the random nature of coherent reflection, the instantaneous frequency (IF) and amplitude envelope of TEOAEs both fluctuate. Multiple reflection components and synchronized spontaneous emissions can further make it difficult to extract the IF by linear transforms. This paper proposes to model TEOAEs as a sum of intrinsic mode-type functions and analyze it by a nonlinear-type time-frequency (T-F) analysis technique called concentration of frequency and time (ConceFT). When tested with synthetic otoacoustic emission signals with possibly multiple oscillatory components, the present method is able to produce clearly visualized traces of individual components on the T-F plane. Further, when the signal is noisy, the proposed method is compared with existing linear and bilinear methods in its accuracy for estimating the fluctuating IF. Results suggest that ConceFT outperforms the best of these methods in terms of optimal transport distance, reducing the error by 10% to 21% when the signal to noise ratio is 10 dB or below.
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Affiliation(s)
- Hau-Tieng Wu
- Department of Mathematics and Department of Statistical Science, Duke University, 120 Science Drive, Durham, North Carolina 27705, USA
| | - Yi-Wen Liu
- Department of Electrical Engineering, National Tsing Hua University, 101 Kuang Fu Road Section 2, Hsinchu 30013, Taiwan
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Elliott SJ, Ni G, Sun L. Fitting pole-zero micromechanical models to cochlear response measurements. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2017; 142:666. [PMID: 28863604 DOI: 10.1121/1.4996128] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
An efficient way of describing the linear micromechanical response of the cochlea is in terms of its poles and zeros. Pole-zero models with local scaling symmetry are derived for both one and two degree-of-freedom micromechanical systems. These elements are then used in a model of the coupled cochlea, which is optimised to minimise the mean square difference between its frequency response and that measured on the basilar membrane inside the mouse cochlea by Lee, Raphael, Xia, Kim, Grillet, Applegate, Ellerbee Bowden, and Oghalai [(2016) J. Neurosci. 36, 8160-8173] and Oghalai Lab [(2015). https://oghalailab.stanford.edu], at different excitation levels. A model with two degree-of-freedom micromechanics generally fits the measurements better than a model with single degree-of-freedom micromechanics, particularly at low excitations where the cochlea is active, except post-mortem conditions, when the cochlea is passive. The model with the best overall fit to the data is found to be one with two degree-of-freedom micromechanics and 3D fluid coupling. Although a unique lumped parameter network cannot be inferred from such a pole-zero description, these fitted results help indicate what properties such a network should have.
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Affiliation(s)
- Stephen J Elliott
- Institute of Sound and Vibration Research, University of Southampton, Highfield Campus, Southampton SO17 1BJ, United Kingdom
| | - Guangjian Ni
- Laboratory of Neural Engineering and Rehabilitation, Department of Biomedical Engineering, College of Precision Instruments and Optoelectronics Engineering and Tianjin International Joint Research Center for Neural Engineering and Academy of Medical Engineering and Translational Medicine, Tianjin University, Tianjin 300072, China
| | - Luyang Sun
- Key Laboratory of Noise and Vibration Research, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, China
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