Hussnain Ali

Inductive link design for medical implants

This paper describes design principles to design and develop a transcutaneous link for medical implants using inductively coupled coils. Parameters which optimize link efficiency have been discussed in the light of previous studies and a simple design methodology to find optimized parameters for Class E amplifier and inductive coils is outlined. Paper also describes design of an indigenously developed transcutaneous link from commercial off-the-shelf components to demonstrate the design process. Simulation and practical results of the link developed at 2.5MHz for 100mW output power are provided. We were able to achieve 40% link efficiency with data rate of 128kbps from laboratory-based discrete electronic components.

Mathematical modeling of an inductive link for optimizing efficiency

Design of an optimized RF transcutaneous link through inductive coils is an arduous design process which involves complex mathematical modeling to search for optimized design parameters. This paper presents a generalized model which encompasses all possible voltage driven circuit realizations of an inductive link and presents a comparison on the bases of link efficiency and voltage gain. Mathematical expressions for the generalized voltage driven model as well as for the equivalent circuit topologies are derived. Moreover effect of different parameters such as resonating impedances on the final relationships is exhaustively analyzed. Optimization is a critical aspect in designing inductive links for medical implants since the link virtually acts as an air-core transformer with relatively low mutual coupling. Therefore, in order to maximize the gain and improve the link efficiency it is very necessary to design the link on optimized parameters. Aim of the analysis is to facilitate the designers in their design process as mathematical relationships for different models and their comparison has never been reported earlier in literature.

A DSK based simplified speech processing module for Cochlear Implant research

A simple yet flexible research module for laboratory experiments in evaluating performance of different speech processing strategies of Cochlear Implant is developed. It enables algorithm development and evaluation through a series of three sub-modules. Software Evaluation Module provides a graphical environment to the researchers to develop new strategies as well as experiment with parametric variation of these strategies. Evaluation is done by means of Waveform Analyzer and audible reconstruction of the synthesized sound. Hardware Evaluation Module evaluates real-time operational performance of the algorithms in DSP environment. It highlights the practical bottlenecks of any algorithm when transferred from software to hardware domain. Finally, Real-time Patient Evaluation Module allows performance evaluation of the developed strategy on actual Cochlear Implant patients. Simple and easy to use GUIs enable clinicians and researchers to experiment with speech processing strategies with great ease and flexibility without requiring advanced programming skills.

A PDA platform for offline processing and streaming of stimuli for cochlear implant research

A PDA-based research platform has been developed for implementing novel speech processing strategies and conducting psychophysical experiments with cochlear implant (CI) research that do not necessarily require real-time processing. The developed interface streams stimuli pulses to a CI unit in an offline mode from a Personal Computer via PDA platform using Windows Sockets (WINSOCK). Front-end of the application is run in MATLAB where stimuli pulses are created. Winsock establishes a TCP/IP connection with the PDA and starts the transmission of stimuli data. Server application installed on the PDA reads the stimulation data and forwards it to the SDIO board in packets where it is forwarded to the cochlear implant unit and pulses are then played in realtime. Versatility and flexibility are the key characteristics of the platform for easy implementation and testing of a wide range of applications and experiments without advanced programming skills.

Efficient algorithm development of CIS speech processing strategy for cochlear implants

Continuous Interleaved Sampling (CIS) is one of the most useful and famous speech processing strategies used in Cochlear Implant speech processors. However, algorithm realization in hardware is a laborious task due to high computation cost of the algorithm. Real-time issues and low-power design demands an optimized realization of algorithm. This paper proposes two techniques to cut the computation cost of CIS by using polyphase filters and by implementing the complete algorithm in frequency domain. About 70% reduction in computation cost can be achieved by using multi-rate, multistage filters; whereas computation cost decreases by a factor of five when the whole algorithm is implemented in frequency domain. Evaluation of the algorithm is done by a laboratory designed algorithm development and evaluation platform. Algorithm flow diagrams and their computation details have been given for comparison. Utilizing the given techniques can remarkably reduce the processor load without any compromise on quality.

Laboratory prototype of cochlear implant: Design and techniques

This paper presents design overview of a low cost prototype of Cochlear Implant developed from commercial off-the-shelf components. Design scope includes speech processing module implemented on a commercial digital signal processor, transcutaneous data and power transceiver developed from a single pair of inductive coils and finally a stimulator circuitry for cochlear stimulation. Different speech processing strategies such as CIS, SMSP and F0/F1 have been implemented and tested using a novel, indigenously developed speech processing research module which evaluates the performance of speech processing strategies in software, hardware and practical scenarios. Design overview, simulations and practical results of an optimized inductive link using Class E Power Amplifier are presented. Link was designed at a carrier frequency of 2.5MHz for 100mW output power. Receiver logic design and stimulator circuitry was implemented using a PIC microcontroller and off-the-shelf electronic components. Results indicate 40% link efficiency with 128kbps data transfer rate. This low cost prototype can be used for undertaking cochlear implant research in laboratories.

The Lombard effect observed in speech produced by cochlear implant users in noisy environments: A naturalistic study

The Lombard effect is an involuntary response speakers experience in the presence of noise during voice communication. This phenomenon is known to cause changes in speech production such as an increase in intensity, pitch structure, formant characteristics, etc., for enhanced audibility in noisy environments. Although well studied for normal hearing listeners, the Lombard effect has received little, if any, attention in the field of cochlear implants (CIs). The objective of this study is to analyze speech production of CI users who are postlingually deafened adults with respect to environmental context. A total of six adult CI users were recruited to produce spontaneous speech in various realistic environments. Acoustic-phonetic analysis was then carried out to characterize their speech production in these environments. The Lombard effect was observed in the speech production of all CI users who participated in this study in adverse listening environments. The results indicate that both suprasegmental (e.g., F0, glottal spectral tilt and vocal intensity) and segmental (e.g., F1 for /i/ and /u/) features were altered in such environments. The analysis from this study suggests that modification of speech production of CI users under the Lombard effect may contribute to some degree an intelligible communication in adverse noisy environments.

Analysis of speech and language communication for cochlear implant users in noisy lombard conditions

Acoustic/linguistic modification of speech production with respect to auditory feedback is an important research domain for robust human-to-human and human-to-machine communication. For instance, in the presence of environmental noise, a speaker experiences the well-known phenomenon termed as Lombard effect. Lombard effect has been well studied for normal hearing listeners as well as for automatic speech/speaker recognition systems. However, limited effort has been employed to study if the speech production of cochlear implant (CI) users is influenced by the auditory feedback. The purpose of this study is to analyze the speech production and natural language model of CI users with respect to environmental changes. A mobile personal audio recording from continuous single-session audio streams collected over an individuals daily life was used for our study. The findings from this study will provide fundamental knowledge on the characteristics of speech production under Lombard effect in CI users. These specific variations in speech production can be leveraged in new algorithm development and further applications in speech systems to benefit cochlear implant users.?

Evaluation and analysis of whispered speech for cochlear implant users: Gender identification and intelligibility

This study investigates the degree to which whispered speech impacts speech perception and gender identification in cochlear implant (CI) users. Listening experiments with six CI subjects under neutral and whispered speech conditions using sentences from the UT-Vocal Effort II corpus (recordings from male and female speakers) were conducted. Results indicated a significant effect of whispering on gender identification and speech intelligibility scores. In addition, no significant effect of talker gender on the speech/gender identification scores was observed. Results also suggested that exposure to longer speech stimuli, and consequently more temporal cues, would not improve gender identification performance in CI subjects.

The CCi-MOBILE Vocoder

The UT-Dallas Costakis Cochlear Implant Mobile (CCi-MOBILE) research platform enables experimental research with hearing-aid (HA) and cochlear-implant (CI) devices. The platform substitutes the clinical sound processor (CI/HA) with an Android smartphone/tablet or a PC as a computing hardware to run custom speech processing algorithms. The flexibility offered by such a setup enables researchers to provide custom-designed electric and acoustic stimuli (EAS) to CIs and HAs bilaterally in a time-synchronized manner. With this bimodal (electric + acoustic) capability, the platform can be used to undertake studies with individuals who either use a CI in one ear and a HA in the contralateral ear, or use hybrid implants in one or both ears. The CCi-MOBILE software suite includes a range of research applications which address different experimental needs. In the present work, a real-time VOCODER is incorporated in the CCi-MOBILE platform to facilitate research involving acoustic simulations of CIs. Two traditional flavors of VOCODER processing are implemented, namely noise-band and sine-wave vocoding. Flexibility is provided to modify processing parameters such as number of channels, frequency band-widths, filter attributes, etc. This flexibility combined with the ability to conduct long-term studies beyond the laboratory in diverse naturalistic acoustic environments will help advance research in psychoacoustics.