Question
What are your thoughts on the use of something like the Quick-SIN or the HINT to evaluate FM-system effectiveness?
Answer
I think that is a wonderful practice to use adaptive procedures in noise as found in the Quick-SIN or HINT. With percent correct scoring there can be floor and ceiling effects that limit the ability to see significant differences in performance (Raffin & Thornton, 1980). We've been using some common phrases that Dr. Erin Schafer at The University of North Texas developed to evaluate speech recognition performance in noise, such as "brush your teeth, "comb his hair", and "bend his knee". The children use a doll to act out the phrases they hear, so there is no confusion with intelligibility. This test can be used with a portable CD player, where the phrases are played from the front speaker (0 degrees azimuth) and the noise from the rear speaker (180 degrees azimuth). The FM transmitter microphone is placed six inches from the cone of the front speaker. The test uses a simple adaptive protocol that finds the signal-to-noise ratio that the child correctly responds 50% of the time. More information about this test can be found in a publication Schafer & Thibodeau (2006) in the American Journal of Audiology.
Here is how we would use the results from this test. Let's say the child gets a signal-to-noise ratio of +10 with the CI alone. Then you add the FM system and you see the child responding at a 0 signal-to-noise ratio. This is a 10 dB improvement in the signal-to-noise ratio! It's a little harder to explain to administrators and parents because you are not just dealing with the more familiar percent correct like. I try to say things like "without the FM they hear my speech with about 10 units of noise. Then with the FM they can hear me with 10 additional units of noise meaning they can tolerate more noise like we have in the classroom". I try to put it in those terms. I haven't actually replicated that same setup with something like the Quick-SIN, but I think that a very similar protocol could work. I think adaptive testing is a very useful tool for us and we need to be looking at it more for use in the clinic.
References
Raffin, M. J., & Thornton, A. R. (1980). Confidence levels for differences between speech-discrimination scores: A research note. Journal of Speech and Hearing Research, 23, 5-18.
Schafer, E. and Thibodeau, L. (2006). Speech recognition in noise in children with cochlear implants while listening in bilateral, bimodal, and FM-system arrangements. American Journal of Audiology. 15(2):114-26.
Dr. Linda Thibodeau is a Professor at the University of Texas at Dallas. She has been at UTD since 1997 where she co-directs the Pediatric Aural Habilitation Training Specialist Project. Prior to that she worked at the University of Texas at Austin, at the University of Texas Speech and Hearing Institute, in otolaryngology clinics, and in the public schools. She teaches in the areas of Amplification and Pediatric Aural Habilitation. Her research involves evaluation of the speech perception of listeners with hearing loss and auditory processing problems as well as evaluation of amplification systems and assistive listening devices (ALDs) designed to help those persons. She consults with several school districts and manufacturers regarding FM arrangements in the classroom. Her interests include serving as the co-chair of the ANSI committee to develop a standard for the Electroacoustic Evaluation of ALDs; and serving as Editor-in-Chief of the Journal of the Academy of Rehabilitative Audiology. She is a 2006 Contributing Editor for Audiology Online.
