Methods of Improving Speech Intelligibility for Listeners with Hearing Resolution Deficit

ABSTRACT: Methods developed for real-time time scale modification (TSM) of speech signal are presented. They are based on the non-uniform, speech rate depended SOLA algorithm (Synchronous Overlap and Add). Influence of the proposed method on the intelligibility of speech was investigated for two separate groups of listeners, i.e. hearing impaired children and elderly listeners. It was shown that for the speech with average rate equal to or higher than 6.48 vowels/s, all of the proposed methods have statistically significant impact on the improvement of speech intelligibility for hearing impaired children with reduced hearing resolution and one of the proposed methods significantly improves comprehension of speech in the group of elderly listeners with reduced hearing resolution. VIRTUAL SLIDES: http://www.diagnosticpathology.diagnomx.eu/vs/206548637176199

DESIGN AND EVALUATION OF PORTABLE PSYCHOACOUSTIC TESTING SYSTEMS

There is an increasing demand for developing portable psychoacoustic testing systems to evaluate the hearing abilities of people. In this thesis, the design, development, and evaluation of portable, flexible, and versatile wired and wireless psychoacoustic testing systems will be presented. The design of the wired system utilizes a USB audio I/O controller chip for communicating with the application software on the host through a USB cable. The wireless system includes two units: a transmitter and a receiver. 2.4GHz RF transceiver chips are employed for wireless communication. Double-side PCBs populated with 0603 SMD were designed and fabricated. To go along with the hardware, software was developed on a handheld device to control and execute several psychoacoustic tests and to log subjective data. Objective measurements and small scale clinical trials were undertaken to test the efficiency of the proposed portable systems

Objective Assessment of Machine Learning Algorithms for Speech Enhancement in Hearing Aids

Speech enhancement in assistive hearing devices has been an area of research for many decades. Noise reduction is particularly challenging because of the wide variety of noise sources and the non-stationarity of speech and noise. Digital signal processing (DSP) algorithms deployed in modern hearing aids for noise reduction rely on certain assumptions on the statistical properties of undesired signals. This could be disadvantageous in accurate estimation of different noise types, which subsequently leads to suboptimal noise reduction. In this research, a relatively unexplored technique based on deep learning, i.e. Recurrent Neural Network (RNN), is used to perform noise reduction and dereverberation for assisting hearing-impaired listeners. For noise reduction, the performance of the deep learning model was evaluated objectively and compared with that of open Master Hearing Aid (openMHA), a conventional signal processing based framework, and a Deep Neural Network (DNN) based model. It was found that the RNN model can suppress noise and improve speech understanding better than the conventional hearing aid noise reduction algorithm and the DNN model. The same RNN model was shown to reduce reverberation components with proper training. A real-time implementation of the deep learning model is also discussed

Frequency and temporal resolution in elderly listeners with good and poor word recognition.

There is a subgroup of elderly listeners with hearing loss who can be characterized by exceptionally poor speech understanding. This study examined the hypothesis that the poor speech-understanding performance of some elderly listeners is associated with disproportionate deficits in temporal resolution and frequency resolution, especially for complex signals. Temporal resolution, as measured by gap detection, and frequency resolution, as measured by the critical ratio, were examined in older listeners with normal hearing, older listeners with hearing loss and good speech-recognition performance, and older listeners with hearing loss and poor speech-recognition performance. Listener performance was evaluated for simple and complex stimuli and for tasks of added complexity. In addition, syllable recognition was assessed in quiet and noise. The principal findings were that older listeners with hearing loss and poor word-recognition performance did not perform differently from older listeners with hearing loss and good word recognition on the temporal resolution measures nor on the spectral resolution measures for relatively simple stimuli. However, frequency resolution was compromised for listeners with poor word-recognition abilities when targets were presented in the context of complex signals. Group differences observed for syllable recognition in quiet were eliminated in the noise condition. Taken together, the findings support the hypothesis that unusual deficits in word- recognition performance among elderly listeners were associated with poor spectral resolution for complex signals

Communications Biophysics

Contains reports on seven research projects split into three sections, with research objective for the final section.National Institutes of Health (Grant 2 PO1 NS 13126)National Institutes of Health (Grant 5 RO1 NS 18682)National Institutes of Health (Grant 1 RO1 NS 20322)National Institutes of Health (Grant 1 RO1 NS 20269)National Institutes of Health (Grant 5 T32 NS 07047)Symbion, Inc.National Institutes of Health (Grant 5 RO1 NS10916)National Institutes of Health (Grant 1 RO1 NS16917)National Science Foundation (Grant BNS83-19874)National Science Foundation (Grant BNS83-19887)National Institutes of Health (Grant 5 RO1 NS12846)National Institutes of Health (Grant 5 RO1 NS21322)National Institutes of Health (Grant 5 RO1 NS 11080

A study on wireless hearing aids system configuration and simulation

Master'sMASTER OF SCIENC

Development and Evaluation of a Real-Time Framework for a Portable Assistive Hearing Device

Testing and verification of digital hearing aid devices, and the embedded software and algorithms can prove to be a challenging task especially taking into account time-to-market considerations. This thesis describes a PC based, real-time, highly configurable framework for the evaluation of audio algorithms. Implementation of audio processing algorithms on such a platform can provide hearing aid designers and manufacturers the ability to test new and existing processing techniques and collect data about their performance in real-life situations, and without the need to develop a prototype device. The platform is based on the Eurotech Catalyst development kit and the Fedora Linux OS, and it utilizes the JACK audio engine to facilitate reliable real-time performance Additionally, we demonstrate the capabilities of this platform by implementing an audio processing chain targeted at improving speech intelligibility for people suffering from auditory neuropathy. Evaluation is performed for both noisy and noise-free environments. Subjective evaluation of the results, using normal hearing listeners and an auditory neuropathy simulator, demonstrates improvement in some conditions

Speech function in persons with Parkinson\u27s disease: effects of environment, task and treatment

Parkinson’s Disease (PD) is a degenerative neurological disease affecting aspects of movement, including speech. Persons with PD are reported to have better speech functioning in the clinical setting than in the home setting, but this has not been quantified. New methodologies in ambulatory measures of speech are emerging that allow investigation of non-clinical settings. The following questions are addressed: Is speech different between environments in PD and in healthy controls? Can clinical tasks predict speech behaviors in the home? Is treatment proven effective by measures in the home? What can we glean from methods of measurement of speech function in the home? The experiment included 13 persons with PD and 12 healthy controls, studied in the clinical and home environments, and 7 of those 13 persons with PD participated in a treatment study. Major findings included: Spontaneous speech intelligibility, not intensity, was the differentiating factor between persons with PD and healthy controls. Intelligibility and intensity were not related. Both groups presented with higher sentence intensity in the home environment. Spontaneous speech intelligibility in the clinic was related to spontaneous speech intelligibility in the home. The Sentence Intelligibility Test emerged as the best predictor of spontaneous speech intelligibility in the home. Differences between pilot treatment groups measured in the home on intensity and intelligibility were not large enough to make a clinical trial feasible. Individual differences may account for many of these results, for example more severely impaired patients may have shown different data. Drawing conclusions regarding the home environment via measures outside the home should be carefully considered. Ambulatory measures of speech are a viable option for studying speech function in non-clinical settings, and technology is advancing. Further investigation is needed to develop methodologies and normative values for speech in the home

The Development of Synthetic Speech Aids for Patients With Acquired Disability

Patients suffering from a variety of speech disorders can benefit from synthetic speech. This study concentrates on the dysarthric patients with acquired speech loss as these patients have intact intellect and are more likely to benefit from synthetic speech. The physical skills of these patients vary enormously and their needs and situations are different. The main part of this work is concerned with the design, development and evaluation of a range of speech aids to meet these varying needs and skills. Three methods of speech synthesis are used and their performance has been investigated by using a Diagnostic Rhyme Test to measure the intelligibility of individual words. The results of this trial showed Adaptive Differential Pulse Code Modulation (ADPCM) to be more intelligible than Linear Predictive Coding (LPC), both these methods being more intelligible than constructive synthesis. A further trial was conducted to measure the speech quality of phrases produced by the synthesisers. This showed listeners preferred listening to phrases constructed of LPC words than to phrases generated using Phoneme based synthesisers. Phrases with mixed LPC and constructed words were preferred to phrases of constructed words. The devices that were developed use different methods of synthesis and the choice of method was guided by these trials. The Pocket Speech Aid is a rapid access limited vocabulary communication aid which uses ADPCM synthesis. Direct selection is the method used to give users access to eight phrases. The Pocket Speech Aid has been very successful in practice. When used as a telephone aid eight out of ten patients increased their communication ability and when used as a conversation prompter ten out of fourteen patients were able to steer the direction of real time conversations. This device has generated a great deal of interest from other centres and the demand for the device which is currently being manufactured confirms that it has a role to play in assisting those with communication difficulties. The Macleod Unit was named after a remarkable patient suffering from Motor Neurone Disease who realised his speech would soon be lost and had the foresight to select a vocabulary and record the words on a cassette recorder. His 625 word vocabulary was transferred to the speech aid which uses an encoding method of word selection. Clinical feedback showed the device to be of benefit for this highly motivated individual but was less successful for other patients in this group who found the cognitive effort to select codes too great. An unlimited vocabulary device based on the commercially available VOTRAX which uses constructive synthesis was developed but this device was rejected because of the robotic sounding voice. A further unlimited vocabulary device prototype, the Uvocom, was designed to improve the speech quality and to investigate if there is a need for an unlimited vocabulary. The Uvocom uses a core vocabulary of 1000 LPC words and uses Phoneme back-up for words not stored in the core vocabulary. Trials with the Uvocom have indicated that quality speech in an unlimited vocabulary device is likely to benefit a small number of patients who have the physical skills to operate such a device. Finally, some indication is given of the directions in which future work could progress based on the proven success of the Pocket Speech Aid