Joshua M. Alexander

Research Interests / Training Areas:

  • Amplification
  • Speech Perception
  • Auditory Perception

Biography:

Joshua M. Alexander received his Ph.D. in Audiology (psychoacoustics) and post-doctoral training in speech perception at the University of Wisconsin- Madison. Before coming to Purdue, he completed both clinical and post-doctoral fellowships at Boys Town National Research Hospital in Omaha, Nebraska.

Research interests focus on auditory processes contributing to speech perception deficits in hearing-impaired listeners and signal processing techniques to overcome them. Ongoing projects include work on frequency-lowering techniques, wide dynamic range compression, and speech enhancement techniques. In 2015, Dr. Alexander was issued a US patent for his novel method of frequency lowering. He has another pending on a technique for speech enhancement. Discovery is aided by an innovative approach by which signal processing techniques like these and realistic hearing aid amplification are simulated in the laboratory on a PC. This allows the researchers in the lab to know precisely the effect that their manipulations have on the acoustic signal as they try to relate listener performance back to psychophysical estimates of cochlear filtering, auditory nerve models, and cognitive processing.

The framework guiding the discovery process involves the interplay of three key components: basic research (speech perception and psychoacoustic deficits); applied research (digital signal processing algorithms intended for hearing aids and automatic speech recognition); and modeling. Ongoing efforts encompass two main lines of research: understanding existing technology and developing new technology. Recently, effort has been directed towards developing auditory nerve models that quantify information in a speech signal to help explain the effects that different signal processing strategies have on speech perception as a function of hearing loss so that better solutions can be devised.

Recent Publications:

Alexander*, J. M., Rallapalli2*, V., (2017).  Acoustic and perceptual effects of amplitude and frequency compression on high-frequency speech.  Journal of the Acoustical Society of America.

Brennan*, M. A., Lewis, D., McCreery, R., Kopun, J., Alexander, J. M. (2017).  Listening effort and speech recognition with frequency compression amplification for children and adults with hearing loss.  Journal of the American Academy of Audiology.

Lllanos2*, F., Alexander, J. M., Stilp, C. E., Kluender, K. R. (2017).  Power spectral entropy as an information-theoretic correlate of manner of articulation in American English.  Journal of the Acoustical Society of America- Express Letters, 141, EL127-EL133.

Winiger2*, A., Alexander*, J. M., Diefendorf, A. (2016).  Minimal hearing loss: From a failure based approach to evidence based practice.  American Journal of Audiology, 25, 232-245.

Plotkowski 2*, A., Alexander*, J. M. (2016).  A sequential sentence test paradigm using revised PRESTO sentence lists.  Journal of the American Academy of Audiology, 27, 647-660.

Alexander, J. M. (2016).  Nonlinear frequency compression: Influence of start frequency and input bandwidth on consonant and vowel recognition.  Journal of the Acoustical Society of America, 139, 938-957.

Brennan*, M. A., McCreery, R., Kopun, J., Alexander, J. M., Lewis, D., Stelmachowicz, P. G. (2016).  Masking release in children with hearing loss when using amplification.  Journal of Speech Language and Hearing Research, 59, 110-121.

Rallapalli2*, V., Alexander*, J. M. (2015).  Neural-Scaled Entropy predicts the effects of nonlinear frequency compression on speech perception.  Journal of the Acoustical Society of America, 138, 3061-3072.

Alexander*, J. M., Masterson2, K. M. (2015).  Effects of WDRC release time and number of channels on output SNR and speech recognition.  Ear and Hearing, 36, e35-e49.

Alexander*, J. M., Kopun, J.G., Stelmachowicz, P. G. (2014).  Effects of frequency compression and frequency transposition on fricative and affricate perception in listeners with normal hearing and mild to moderate hearing loss.  Ear and Hearing, 35, 519-532.

McCreery*, R. W., Alexander, J. M., Brennan, M. A., Hoover, B., Kopun, J., Stelmachowicz, P. G. (2014).  The influence of audio-visual exposure on speech recognition with nonlinear frequency compression for children and adults with hearing loss.  Ear and Hearing, 35, 440-447.

Brennan*, M. A., McCreery, R., Kopun, J., Alexander, J. M., Lewis, D., Stelmachowicz, P. G. (2014).  “Paired comparisons of nonlinear frequency compression, extended bandwidth, and restricted bandwidth hearing-aid processing for children and adults with hearing loss.  Journal of the American Academy of Audiology, 25, 983-998.

Joshua Alexander
Associate Professor

Lyles-Porter Hall, Room 3076
Phone: 765-494-4091
alexan14@purdue.edu

Lab:
Purdue Experimental Amplification Research (EAR) Lab

Speech, Language, & Hearing Sciences, Lyles-Porter Hall, 715 Clinic Drive, West Lafayette, IN 47907-2122, PH: (765) 494-3789

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