Research Sources and Citations

Speech Perception and SNR Research

The relationship between signal-to-noise ratio and speech understanding is one of the most extensively studied topics in audiology. Our SNR-to-intelligibility conversion model is based on decades of psychoacoustic research.

• Killion, M.C. (1997). "SNR loss: I can hear what people say, but I can't understand them." The Hearing Review, 4(12), 8-14.
• Plomp, R. (1986). "A signal-to-noise ratio model for the speech-reception threshold of the hearing impaired." Journal of Speech and Hearing Research, 29, 146-154.
• Nilsson, M., Soli, S.D., & Sullivan, J.A. (1994). "Development of the Hearing in Noise Test for the measurement of speech reception thresholds in quiet and in noise." Journal of the Acoustical Society of America, 95, 1085-1099.
• Wilson, R.H. (2003). "Development of a speech-in-multitalker-babble paradigm to assess word-recognition performance." Journal of the American Academy of Audiology, 14(9), 453-470.
• Smeds, K., Wolters, F., & Rung, M. (2015). "Estimation of signal-to-noise ratios in realistic sound scenarios." Journal of the American Academy of Audiology, 26(2), 183-196.

Directional Microphone and Beamforming Research

Directional microphone technology is the primary on-ear mechanism for improving SNR. The benefit values used in HearMetrics are derived from clinical studies measuring real-world directional advantage.

• Ricketts, T.A. (2001). "Directional hearing aids." Trends in Amplification, 5(4), 139-176.
• Bentler, R.A. (2005). "Effectiveness of directional microphones and noise reduction schemes in hearing aids: A systematic review of the evidence." Journal of the American Academy of Audiology, 16(7), 473-484.
• Picou, E.M., Aspell, E., & Ricketts, T.A. (2014). "Potential benefits and limitations of three types of directional processing in hearing aids." Ear and Hearing, 35(3), 339-352.
• Froehlich, M., Freels, K., & Powers, T.A. (2015). "Speech recognition benefit of digital wireless binaural hearing aids." Hearing Review, 22(11), 44.

Remote Microphone Research

Remote microphones provide the largest measurable SNR improvement of any hearing aid accessory. Our remote microphone benefit values are based on published clinical data.

• Thibodeau, L. (2014). "Comparison of speech recognition with adaptive digital and FM remote microphone hearing assistance technology by listeners who use hearing aids." American Journal of Audiology, 23(2), 201-210.
• Wolfe, J., et al. (2013). "Evaluation of speech recognition of cochlear implant recipients using a personal digital adaptive radio frequency system." Journal of the American Academy of Audiology, 24(8), 714-724.
• De Ceulaer, G., et al. (2016). "Speech understanding in noise with the Roger Pen, Roger Focus, and school FM with the HiRes 90K Advantage cochlear implant." Cochlear Implants International, 17(S1), 93-98.
• Phonak (2023). "Roger technology: Bridging the understanding gap in noise." Phonak Field Study News.

Hearing Loss and Speech Understanding

The impact of hearing loss severity on speech understanding in noise is well-documented. Our hearing loss impact model uses the relationship between pure tone average (PTA) and SNR loss.

• Killion, M.C., & Niquette, P.A. (2000). "What can the pure-tone audiogram tell us about a patient's SNR loss?" The Hearing Journal, 53(3), 46-53.
• Dubno, J.R., Horwitz, A.R., & Ahlstrom, J.B. (2002). "Benefit of modulated maskers for speech recognition by younger and older adults with normal hearing." Journal of the Acoustical Society of America, 111, 2897-2907.
• Humes, L.E. (2007). "The contributions of audibility and cognitive factors to the benefit provided by amplified speech to older adults." Journal of the American Academy of Audiology, 18(7), 590-603.

Acoustic Environment and Restaurant Noise

Understanding real-world noise levels is essential for realistic hearing aid modeling. Our noise environment defaults are based on published acoustic measurements.

• Olsen, W.O. (1998). "Average speech levels and spectra in various speaking/listening conditions: A summary of the Pearson, Bennett, & Fidell (1977) report." American Journal of Audiology, 7(2), 21-25.
• Smeds, K., Wolters, F., & Rung, M. (2015). "Estimation of signal-to-noise ratios in realistic sound scenarios." Journal of the American Academy of Audiology, 26(2), 183-196.
• Pearsons, K.S., Bennett, R.L., & Fidell, S. (1977). "Speech levels in various noise environments." EPA Report 600/1-77-025. US Environmental Protection Agency.

Independent Testing Organizations

HearMetrics references independent hearing aid testing data from these organizations:

• HearAdvisor — Independent hearing aid testing lab that measures speech-in-noise performance, sound quality, and hearing aid features using standardized protocols.
• HearingTracker — Consumer-focused hearing aid information platform with professional reviews and comparison data.
• NIDCD (National Institute on Deafness and Other Communication Disorders) — Federal agency supporting research on hearing, balance, and communication.

Methodology

For a detailed explanation of how HearMetrics calculates SNR improvements, models hearing loss impact, and generates speech-in-noise simulations, see our About the Model page.

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