Does non-linear frequency compression (NFC) work for adults?
Yes, for many individuals NFC will improve the detection of high-frequency speech and environmental sounds without creating unpleasant sound quality and consonant confusions. Often, benefit has been documented in studies when the clinician first met broadband targets for audibility and then fine-tuned NFC parameters to ensure audibility goals were met. These adjustments tended to involve a strengthening (decreasing the cut-off frequency) of NFC.
Simpson (2005) applied a prototype of NFC on adults with moderate to severe sloping hearing losses. At the group level, NFC significantly improved detection of affricate and fricative consonants. In a follow-up study with steeply sloping loses (Simpson, 2006), benefit was not seen. However, this could have been due to the fact that prototypes were used, subjects did not have previous hearing aid experience, or the settings were not optimized to provide benefit for these losses.
At the University of Western Ontario, Danielle Glista and colleagues (2009) evaluated NFC with adults with moderate to profound sloping hearing losses. Five out of 13 subjects obtained significant benefit from NFC.
Rachel Ellis, as part of her doctoral thesis at University of Manchester (2012), found that 9 out of 11 adults with bilateral sensorineural hearing loss (SNHL) demonstrated a significant improvement on speech in quiet and noise measures with NFC.
Andrew John and colleagues (2013) demonstrated a significant effect of NFC with 28 adult subjects with asymmetric hearing loss. Gains were seen on high-frequency speech tests and self-reported gains in sound quality and speech understanding in quiet. Benefit was not seen in noise, however in a previous study with children (Wolfe, et al., 2011) Dr. Wolfe found that improvement in noise only became significant after six months of use.
This Ask the Expert was taken from the article and text course, Sound Bytes on SoundRecover – view the complete article for more information.
Ellis, R. J. (2012). Benefit and predictors of outcome from frequency compression hearing aid use. A thesis submitted to the University of Manchester for the degree of Doctor of Philosophy. Faculty of Medical and Human Sciences.
Glista, D., Scollie, S., Bagatto, M., Seewald, R., Parsa, V., & Johnson, A. (2009). Evaluation of nonlinear frequency compression: Clinical outcomes. International Journal of Audiology, 48(1), 632–644. doi: 10.1080/14992020902971349.
John, A., Wolfe, J., Schafer, E., Hudson, M., Fox, K., Wheeler, J., et al. (2013). In asymmetric high frequency hearing loss, NLFC helps. The Hearing Journal, 66(9), 26-29.
Simpson, A., Hersbach, A., & McDermott H. (2005). Improvements in speech perception with an experimental non-linear frequency compression hearing device. International Journal of Audiology, 44(5), 281-292.
Simpson, A., Hersbach, A., & McDermott, H. (2006). Frequency-compression outcomes in listeners with steeply sloping audiograms. International Journal of Audiology, 45(11), 619-629.
Wolfe, J., John, A., Schafer, E., Nyffeler, M., Boretzki, M., & Caraway, T., et al. (2011). Long-term effects of non-linear frequency compression for children with moderate hearing loss. International Journal of Audiology, 50(6), 396–404. doi: 10.3109/14992027.2010.551788.