Developing a Portable, Real-Time Platform for Cochlear Implant Studies Based on NI LabVIEW Software

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"LabVIEW and the LabVIEW Mobile Module provide software flexibility, giving our signal processing software the ability to run on any PDA irrespective of the PDA processor. "

- Nasser Kehtarnavaz, University of Texas at Dallas

The Challenge:
Developing a cost-effective, portable, easy-to-use program and interactive platform for cochlear implant researchers and clinicians.

The Solution:
Using LabVIEW software and the LabVIEW Mobile Module to develop a real-time, cost-effective portable platform that cochlear implant researchers can use to easily examine, modify, and interact with cochlear implant signal processing algorithms.

Author(s):
Nasser Kehtarnavaz - University of Texas at Dallas
Philip Loizou - University of Texas at Dallas

Cochlear implants are prosthetic devices that provide partial hearing to profoundly deaf people. The FDA approved these devices for adults in 1984 and for children in 1990. Now, there are more than 110,000 people worldwide fitted with cochlear implants. Unlike hearing aids, cochlear implants do not amplify speech signals; rather, they emulate the functions of the outer, middle, and inner ear.

In an ear that functions normally, the basilar membrane in the inner ear divides an acoustic signal into different frequencies that cause vibrations at different points in the cochlea. High frequencies cause vibrations at the base and low frequencies cause vibrations at the apex of the cochlea. When damage to the connection between hair cells and the basilar membrane causes deafness, cochlear implants are used to perform the hair cell functions to directly stimulate the neurons.

Cochlear Implant Components

Cochlear implants feature two main parts. One part, which is placed inside the ear, consists of an electrode array stimulating the auditory nerve fibers. The other part, which resides outside the body, consists of a microphone to capture audio signals, a speech processor to perform the function of the inner ear by extracting the envelope of the input acoustic signal in different frequency bands, and a transmitter to transmit appropriate pulses to the electrodes.

Currently, the research platforms for the development and evaluation of new signal processing algorithms are not portable. The only available portable platform, the SPEAR3, requires assembly language programming. Researchers and clinicians are searching for an interactive research platform that is cost-effective, portable, easy to program, and interactive.

As part of a contract funded by the National Institutes of Health (NIH), our research team at the University of Texas at Dallas is working to develop a cochlear implant research platform for researchers and clinicians based on personal digital assistants (PDAs).

Signal Processing with LabVIEW

Different cochlear implant manufacturers use different methods to encode audio signal frequency content. Continuous interleaved sampling (CIS) is the most commonly used algorithm. We normally use noise band vocoder synthesis to assess the processed audio signal quality. In our portable solution, we use LabVIEW software to gain interactivity and programming ease.

To achieve real-time performance, we adopted a hybrid programming approach, for which we used an ANSI C code dynamic link library (DLL) within the LabVIEW graphical programming environment for the filtering process. With the LabVIEW front panel, we easily changed various signal processing parameters such as the number of frequency bands, cutoff frequencies, and sampling frequency.

LabVIEW and the LabVIEW Mobile Module provide software flexibility, giving our signal processing software the ability to run on any PDA irrespective of the PDA processor. In addition, LabVIEW can run the same software on PC platforms with no modification when portability is not required.

Author Information:
Nasser Kehtarnavaz
University of Texas at Dallas
800 W. Campbell Road
Richardson, TX 75080-3021
Tel: (972) 883-6838
Fax: (972) 883-2710
kehtar@utdallas.edu

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