Directional Hearing Aids

Abstract

When asking individuals with hearing impairment to identify the situations for which the most communication difficulty is encountered, listening in nioise seems to be nearly universally mentioned. In fact, I would venture that if queried, almost no patient would refuse the offer of improved levels for sounds of interest in relation to the level of background noise. Improving the signal-to-noise ratio (SNR) for listeners with al, 1982;Groen, 1969;Killion, 1997;Plomp, 1976;Schum, 1996;Sutter, 1985). Children with hearing impairment appear to be even more negatively effected by poor SNR (Boothroyd et al., 1996;Crandell, 1993;Crandell and Smaldino, 2000;Finitzo-Hieber and Tillman, 1978), leading the American Speech-Language-Hearing-Association (Bess et al., 1996), and others (Berg, 1993;Bistafa and Bradley, 2000;Blair, 1990;Smaldino and Crandell, 1995), to recommend SNRs of at least +15 to +30 dB in educational settings. Unfortunately, most classrooms have SNRs between -6 and + 6 dB, making learning in such environments difficult (Bess et al., 1984;Crandell and Smaldino, 2000).Results from past investigations offer clear evidence that listening in poor SNRs is a significant problem for listeners with sensorineural hearing loss. Listening problems in noisy environments can be devastating, and lead some listeners with hearing loss to avoid difficult listening situations, resulting in withdrawal and greater isolation, potentially impacting their overall quality of life in a negative way (Jackson, 1997;McCay, 1996;Mulrow et al., 1990). Hearing aids represent a common rehabilitation method for listeners with sensorineural hearing loss. Hearing aids using standard (omnidirectional) microphones, while effective at increasing audibility for speech and other sounds, are largely ineffective in improving inadequate SNR conditions whether they use analog (Killion and

Effect of low-frequency gain and venting effects on the benefit derived from directionality and noise reduction in hearing aids

“…This finding is in agreement with results presented by Pumford et al (2000), and Ricketts et al (2001). Further, the overall average directional benefit of 2.4 dB measured in this study is in agreement with Flynn (2004) and Fabry (2006), who measured the directional benefit obtained with modern open-fit hearing aids, and it is lower than typical benefit values reported for closed moulds (Ricketts, 2001).…”

“…In optimum conditions, directional benefit values reported in the literature correspond to changes in the signal-to-noise ratio (SNR) from 5.5 to 11 dB, which translates into a significant improvement in speech recognition in noise (Ricketts, 2001). Therefore, optimizing directionality would seem very important.…”

Using hearing aid adaptive directional microphones to enhance cochlear implant performance

“…Directional microphones are microphones that more sensitive to sounds coming from the front than other directions. They have been widely used in hearing aids to reduce background noise, improve sound quality, and enhance listening comfort (Valente, 1999;Ricketts, 2001;Chung, 2004). Yet only one cochlear implant manufacturer has incorporated directional microphones into its cochlear implants.…”

Predictive Measures of Directional Benefit Part 1: Estimating the Directivity Index on a Manikin

“…As SDPs are computed in free field and far field (re: DMHA) conditions, this same data can be used to calculate DI. For DMHAs, information from two-dimensional spatial directivity patterns collected in free field and on KEMAR is typically used to compute the DIs (e.g., Fortune, 1997;Ricketts, 2001). Referring to Equation 4, DI is mathematically defined with the stipulation that the DUT has vertical symmetry.…”

“…When a DMHA is evaluated on a manikin, such as KEMAR, the stipulation is violated, as vertical symmetry (re: horizontal plane) no longer exists (Bentler & Dittberner, 1999;Dittberner & Bentler, 2002;Dittberner, Li, & Bentler, 2001). Unfortunately, both academic and industry researchers continue to report DI values on KEMAR based on two-dimensional spatial directivity pattern data (Fortune, 1997;Olsen & Hagerman, 2002;Preves, 1997;Ricketts, 2001;Ricketts & Dhar, 1999;Ricketts & Mueller, 1999).…”