Modified Verification Approaches for Frequency Lowering Devices

Providing effective hearing aid fittings for high-frequency hearing loss is a challenging and important clinical task. The importance of this task becomes even more apparent when considering the development of speech and language skills in the hearing-impaired pediatric population. Current research suggests that children require audibility of a broad bandwidth of speech for optimal access to high-frequency speech cues and that hearing loss can impede normal development of affricate and fricative production (Moeller et al., 2007; Stelmachowicz, Pittman, Hoover, Lewis, & Moeller, 2004). Despite recent successful attempts by hearing aid manufacturers to decrease acoustic feedback and improve amplification of the high frequencies, gain and/or feedback constraints remain a factor in hearing aid fitting, particularly with significant high-frequency hearing loss. Current research suggests that frequency lowering hearing aid technology can help amplify highfrequency sounds (e.g., /s/, /∫/) for listeners with high-frequency hearing loss (Auriemmo et al., 2009; Glista et al., 2009; Kuk, Keenan, Korhonen, & Lau, in press; Wolfe, Caraway, John, Schafer, & Nyffeler, 2009). Such technology includes digital signal processing algorithms such as frequency transposition and frequency compression. Given the numerous frequency lowering hearing aids currently available on the market, providing information to clinicians on how to fit and fine-tune this type of technology is increasingly important. This article will focus on electroacoustic verification considerations for fitting frequency lowering technologies. We will present a case example of verification using one type of frequency lowering technology: multichannel, nonlinear frequency compression signal processing.