A novel VOCODER for cochlear implants.

A new VOCODER-based speech processing strategy for cochlear implants is presented. The proposed method improves upon existing VOCODER techniques in time-frequency resolution and can offer higher noise immunity. The presented method is based on the effective tracking of nonstationary sinusoid components using a non-linear sinusoid tracking algorithm (STA). The structure of the proposed technique, as well as the underlying STA are presented. It is expected that the improvement in time-frequency resolution will offer superior performance in cochlear implants, as well as improvements in speech coding applications. An eight-band version of the proposed technique is presented and superior performance to existing techniques is shown.

A novel approach for Doppler blood flow measurement.

A new approach to frequency estimation for the velocity estimation in Doppler ultrasound blood flow analysis is presented. The basis of the approach is an adaptive sinusoid-tracking algorithm which is effective in extracting nonstationary signals from within noise and estimating their time-varying parameters, such as the frequency, over time. The preliminary studies conducted using simulated signals show the potential of this approach in estimating Doppler frequency shifts under noisy conditions. A qualitative comparison with the short-time Fourier transform (STFT) is presented to show the advantages of the proposed technique over the STFT. The proposed approach offers advantages over conventional time-frequency analysis techniques in terms of high time-frequency resolution and high noise immunity.

High-resolution analysis of transient evoked otoacoustic emissions.

A new decomposition and time-frequency method applied to the estimation of transient evoked otoacoustic emissions (TEOAEs) is presented. TEOAEs are low-level signals in response to auditory stimuli that are used to monitor the functionality of the cochlea. TEOAE parameter estimation is challenging due to the short duration of the signal (about 20ms) and its highly nonstationary nature. Existing time-frequency methods are incapable of providing accurate estimates of the components within the TEOAE signal. The proposed decomposition and time-frequency method is based on the effective tracking of nonstationary sinusoidal components using a nonlinear iterative sinusoid tracking algorithm. The presented technique improves upon existing techniques by offering a high time-frequency resolution and is capable of providing accurate estimates of components within a TEOAE signal. The structure of the proposed decomposition technique as well as the underlying algorithm are presented. Simulation results are presented to show the performance of the proposed technique. Its performance is also demonstrated on a clinically recorded signal.

A labview-based GUI for the measurement of otoacoustic emissions.

This paper presents the outcome of a software development project aimed at creating a stand-alone user-friendly signal processing algorithm for the estimation of distortion product otoacoustic emission (OAE) signals. OAE testing is one of the most commonly used methods of first screening of newborns' hearing. Most of the currently available commercial devices rely upon averaging long strings of data and subsequent discrete Fourier analysis to estimate low level OAE signals from within the background noise in the presence of the strong stimuli. The main shortcoming of the presently employed technology is the need for long measurement time and its low noise immunity. The result of the software development project presented here is a graphical user interface (GUI) module that implements a recently introduced adaptive technique of OAE signal estimation. This software module is easy to use and is freely disseminated on the Internet for the use of the hearing research community. This GUI module allows loading of the a priori recorded OAE signals into the workspace, and provides the user with interactive instructions for the OAE signal estimation. Moreover, the user can generate simulated OAE signals to objectively evaluate the performance capability of the implemented signal processing technique.

A software module for the adaptive estimation of steady state auditory evoked potentials.

A graphical user interface (GUI) implementing a novel technique of fast estimation of steady state auditory evoked potentials (SSAEPs) for rapid assessment of the functionality of the human auditory nervous system is presented. The proposed signal estimator has shown great promise in the fast extraction of weak signals buried under large amounts of noise such as the case with SSAEP signals. Currently, the main technical impediment in the widespread clinical use of the SSAEP testing for hearing assessment is the excessively long measurement time needed for the estimation process due to the presence of large amounts of background noise. The presented software module that is publicly disseminated through the Internet is meant to facilitate the use of an efficient signal processing technique by the hearing researchers. The software environment allows for loading previously recorded SSAEP signals into the workspace for analysis. Moreover, it enables the user to add simulated SSAEP signals to the background EEG for the purpose of testing the capability of the underlying signal processing algorithm.

An interactive software module for DPOAE signal estimation.

This work presents a freely downloadable software module for the estimation of distortion product otoacoustic emission (DPOAE) signals based on a novel adaptive signal processing technique of measurement of signals under large amounts of noise. DPOAE signal estimation is an effective method of testing the human peripheral auditory function and is extensively used in newborn hearing screening. Current technology is based on the averaging of long strings of data and subsequent Fourier analysis, and suffers from the need for relatively long measurement time and acoustically insulated examination rooms. The method presented in this work features structural simplicity which renders it particularly attractive for implementation on both software and hardware platforms. As such, a fully functional software implementation of the proposed algorithm is developed and is made publicly available for free distribution to researchers in the area. The proposed technique offers a high degree of immunity with regard to background noise and parameter variations. Compared to conventional methods, the proposed method offers a shorter measurement time which is of significant value in clinical examinations. Performance of the proposed method is demonstrated with the aid of computer simulation and is verified in laboratory using recorded clinical data. Snapshots of the developed software environment analyzing both simulated and real clinical data are also presented.

A novel method of estimation of DPOAE signals.

A new method of measurement of distortion product otoacoustic emission (DPOAE) signal level based on a recently introduced nonlinear adaptive method of extraction of nonstationary sinusoids is presented. Essentially, three units of such an algorithm are employed to extract and measure the two stimuli and the DPOAE signal. Each unit has the capability of locking on a specified sinusoidal component of the input signal and tracking its variations over time. Performance of the proposed method is demonstrated with the aid of computer simulations and is verified in laboratory using recorded clinical data. Comparison is made between the proposed technique and existing methods. The proposed method features structural simplicity which renders it particularly attractive for implementation on both software and hardware platforms. It offers a high degree of immunity with regard to background noise and parameter variations. Compared to conventional methods, the proposed method offers a shorter measurement time which is of significant value in clinical examinations.

A new adaptive technique of estimation of steady state auditory evoked potentials.

A novel technique of fast estimation of steady state auditory evoked potentials (SSAEPs) for rapid assessment of the functionality of the human auditory nervous system is presented. The proposed SSAEP signal estimation is based on a new nonlinear adaptive signal processing method that has shown a great promise in the fast extraction of weak signals buried under large amounts of noise. Currently, the main technical impediment in the widespread clinical use of the SSAEP testing for hearing assessment is the excessively long measurement time needed for the estimation process due to the presence of large amounts of background noise. The studies in this paper show significant reduction in the measurement time achieved by the proposed technique.

A novel method of estimation of DPOAE signals.

A new method of measurement of DPOAE signal level based on a recently introduced nonlinear adaptive method of extraction of nonstationary sinusoids is presented. Essentially, three units of such an algorithm are employed to extract and measure the two stimuli and the DPOAE signal. Each unit has the capability of locking on a specified sinusoidal component of the input signal and tracking its variations over time. Performance of the proposed method is demonstrated with the aid of computer simulation and is verified in laboratory using recorded clinical data. Comparison is made between the proposed technique and existing methods. The proposed method features structural simplicity which renders it particularly attractive for implementation on both software and hardware platforms. It offers a high degree of immunity with regard to background noise and parameter variations. Compared to conventional methods, the proposed method offers a shorter measurement time which is of significant value in clinical examinations.

A direct method of estimation of stimulus frequency otoacoustic emissions.

A novel technique of direct estimation of stimulus frequency otoacoustic emission (SFOAE) signals is proposed. SFOAE signals have been the subject of much research because of their value in providing information about the structure and health of the human auditory system. Current methods of estimation of SFOAE signals are indirect in the sense that the use of suppressor tones is inevitable and the SFOAE signals are estimated indirectly by virtue of a nonlinear residual time-domain technique. Conventional signal processing techniques do not provide any means of direct estimation of SFOAE signals given that both the stimulus and the otoacoustic emission are at the same frequency. The studies conducted through testing of the proposed SFOAE estimation technique on simulated data show good performance of the proposed technique.