Browsing by Author "Tokgoz, Serkan"
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Item Development and Analysis of Real-Time Acoustic Feedback Cancellation and a Clinical Testing Simulator for Hearing Studies(2018-07-18) Tokgoz, Serkan; Panahi, Issa M.S.Acoustic feedback stems from acoustic coupling between the loudspeaker and microphone in hearing systems. Unpleasant outcomes of acoustic feedback, such as howling and whistling sounds, are major complaints of people with hearing impairment. As the size of hearing aid devices (HADs) have shrunk and the closed loop made by the feedback path has increased, acoustic feedback cancellation (AFC) methods have become more challenging for researchers. To overcome this problem, standard adaptive filters are commonly used to reduce the acoustic feedback. However, these methods are prone to biased estimations of the feedback path transfer function whenever the speech and feedback signals are correlated. The larger bias estimations worsen the performance of the system. The increased interest in the feedback cancellation problem has focused on the need for efficient AFC techniques. The noise injection method is one of many that is utilized to reduce the effect of acoustic feedback on HADs. This thesis proposes the development and analysis of real-time implementation of the noise injection method in changing room acoustics, a noise injection algorithm controlled by Spectral Flux feature-based voice activity detector (VAD). Objective evaluations were carried out in noisy conditions. Simulation results showed that the proposed methods are efficient in eliminating acoustic feedback. Additionally, real-time development and analysis for smartphone applications that can cancel acoustic feedback without distortion has been completed. In addition to feedback cancellation analysis, this work covers development of clinical testing software which is used in clinical testing stage to evaluate subjects’ hearing ability in noisy environments with various Signal-to-noise ratio (SNR) values.Item Signal Processing Algorithms for Smartphone-Based Hearing Aid Platform; Applications and Clinical Testing(2022-05-01T05:00:00.000Z) Tokgoz, Serkan; Panahi, Issa M.S.; Hoyt, Kenneth; Thibodeau, Linda M.; Kiasaleh, Kamran; Tamil, LakshmanDigital signal processing algorithms are widely utilized in hearing aid applications to im- prove the quality of speech. The signal processing pipeline for speech involves several crucial components that enhance hearing-impaired people’s listening. This thesis covers the devel- opment of novel methods that can be used in the speech processing pipeline and clinical testing. Each chapter of the dissertation focuses on the components of the speech process- ing pipeline for smartphone-based hearing aid setup. The first algorithm, speech source localization (SSL), which identifies the direction of the talker of interest using multiple mi- crophones, is discussed. A speaker identification method is proposed as an assistive system to the pipeline, and it can be used to boost the overall system’s performance. A clinical testing system is developed to evaluate the new signal processing algorithms. An approach is developed to use multiple microphones of iPhone simultaneously for real-time low-latency audio applications. Real-time integration of several signal processing modules that appear in digital hearing aids is developed as smartphone apps. Subjective evaluations are conducted for the proposed methods to show noticeable improvements and compared with state of the art methods. Additionally, the implementation of the proposed methods is explained on smartphones and computers.