In a recent MarkeTrak survey (Ref. 1) Kochkin noted that consumers expect high performance in multiple listening situations. However, only one in four hearing aid wearers was satisfied in as many as 75% of the situations they encountered. Kochkin's data also indicated that satisfaction and performance can be improved across a wider range of listening situations by using hearing aids which combine multiple features such as multiple memories, multiple channels, and multiple microphones2. Combining such features provides the professional with greater flexibility and the ability to tailor amplification to specific listening situations.
The Unison™ line of hearing instruments was conceived to offer fitters maximum flexibility, and wearers the highest possible value for their money. For example, Unison 6 offers six independent channels, four processing strategy choices, three programmable memories, two feedback managers (multiband and adaptive) and Easy t-coil for automatic hassle-free telephone use. All of these features are available with Unison at an affordable price to provide hearing instrument wearers with the best possible value. The economy class is the fastest growing segment in the hearing aid market and Unison has been designed to be the most fully featured product in that class. Table 1 contains a breakdown of all of features available in the entire Unison line.
Table 1 - Summary of Key Features of Unison™
Table 1. Unison 2 and Unison 4 comprise the original line. Unison 6, Unison 3 and Unison E (Essential) make up the new models that are now available.
The Unison fitting philosophy is based on the principle of providing independent programmable memories to optimize performance in specific listening environments. This approach is consistent with Kochkin's findings above. The fitter can choose between WDRC, Automatic Signal Processing (ASP), Adaptive Compression (AC) or Linear Limiting (LL). Up to three different processing strategies can be applied to a Unison fitting, one in each memory. The wearers have the ability to cycle through those processing strategies at their discretion to obtain optimal performance in different listening situations.
A Case in Point
Take the example of a typical new hearing aid wearer. This could be a 70-year-old gentleman with mild to moderate symmetrical, sensorineural hearing loss. He complains that he cannot hear his grandchildren when they come to visit. He has difficulty understanding conversations at the social club he visits twice a week. He would also like to hear better when conversing on the telephone. The initial fitting would go as follows:
A pair of Unison 6 ITCs is ordered with an Easy t-coil in the left hearing aid. The default listening situations for a mild/moderate hearing loss will automatically be chosen by the Unifit™ software to include: P1 = Quiet/Match Target, P2 = Group/Party Noise and P3 = Telephone. The software will also recommend a WDRC processing strategy for P1, ASP for P2 and Linear for P3. Default processing strategies will differ across listening environments and hearing loss configurations. Unifit defaults for Unison 6 are shown in Table 2.
Table 2- Unison™ 6 Default Settings
Table 2. Default processing strategies for all possible listening environments by configuration of hearing loss. For further information about Processing Strategies for different hearing losses see: (Ref. 3)
Program 1
Our gentleman will be able to use WDRC processing in quiet to improve his ability to understand the soft high-pitched voices of his grandchildren. (Ref. 4,5) For this listening environment, his microphones will be omnidirectional. He will know his volume controls are properly set when he hears the beeps from the ideal volume indicators. The hearing aids will provide maximum boost for soft speech using the WDRC processing strategy. Should he require considerable venting to alleviate occlusion, the adaptive feedback canceller will engage to quickly interrupt any possible feedback loops. (Ref. 6) If he requires so much gain that chronic feedback occurs, the multiband feedback manager could also be run at the time of the fitting.
Program 2
This gentleman may only attend his social club two nights a week, but he goes there to socialize. He wishes to converse naturally in a room containing anywhere from five to twenty-five individuals. Some or all of them may be speaking at any one time. For this situation, he switches to his second program. The second program has been optimized for a party situation. The processing strategy switches from WDRC to ASP, with automatic attenuation of low-frequency signals at higher input levels. Multi-channel WDRC is applied in the low frequencies and linear processing is applied to high-frequency inputs. The directional microphones are also engaged to reduce background noise. These two features working together provide optimal comfort in the low frequencies by attenuating noises from behind him and compressing high- level inputs that can originate from any direction. Meanwhile the signal-to-noise ratio is maximized for desirable signals from in front of him by applying linear amplification to high-frequency speech within the target area of the directional microphones. (Ref. 7-10)
Program 3
Another issue that this gentleman mentions is difficulty understanding telephone conversations. An automatic telecoil feature called Easy t-coil is added to his left hearing aid. A small magnet attached to the telephone handset automatically activates this feature. When he picks up the telephone, the hearing aid switches directly to program 3. He hears three beeps telling him that the t-coil is properly activated. He then begins to talk on the telephone without ever having to touch the hearing aid. As he removes the telephone handset from his ear, the hearing aid switches back to the original program (either P1 or P2) that he was using before picking up the phone. He hears one beep if he is returning to P1 or two beeps if returning to P2. The beeps tell him what program his hearing aid is in throughout the day, even when he cycles automatically in and out of the telephone program.
Summary
The Unison family of digital products has been developed to provide fitters with maximum flexibility and wearers with maximum value in an economy class instrument. Four processing strategies are provided to customize performance in up to nine distinct listening environments. Several convenience features such as the ideal volume indicator, Easy t-coil and two different feedback managers have been included to provide the best possible performance with the greatest convenience of any hearing aid in its class. This case study provides a realistic example of how all of these features may be combined to solve the most common problems encountered by real hearing aid wearers.
References
- Kochkin, S. (2002) MarkeTrak VI: 10-year customer satisfaction trends in the US hearing instrument market. Hear Rev 9 (10), 14-25, 46
- Kochkin, S. (1996) Customer satisfaction and subjective benefit with high-performance hearing instruments. Hearing Review 3 (12), 16-26
- Hayes, D. (2004) Multiple processing strategies to accommodate various listening preferences.
- Moore, B. et al. (1992) Effects of the fitting parameters of a two-channel compression system on the intelligibility of speech in quiet and in noise. British Journal of Audiology 26 (Dec), 369-379
- Vonlanthen, A. (2000) Basic Signal Processing Strategies. In Hearing instrument technology for the hearing healthcare professional (Danhauer, J., ed.), pp. 136-141, Singular
- Hayes, D. (2003) Real-time system offers advantages for controlling feedback. Hearing Journal 56 (4), 41-47
- Dempsey, J.J. (1987) Effect of automatic signal-processing amplification on speech recognition in noise for persons with sensorineural hearing loss. Ann Otol Rhinol Laryngol 96 (3 Pt 1), 251-253
- van Tasell, D.J. et al. (1988) Effects of an adaptive filter hearing aid on speech recognition in noise by hearing-impaired subjects. Ear Hear 9 (1), 15-21
- Stein, L. et al. (1989) Speech recognition measures with noise suppression hearing aids using a single-subject experimental design. Ear Hear 10 (6), 375-381
- Fabry, D.A. et al. (1993) Do adaptive frequency response (AFR) hearing aids reduce 'upward spread' of masking? J Rehabil Res Dev 30 (3), 318-325
This article was submitted to Audiology Online by Donald Hayes, PhD, Manager of Audiology Research and Training, Unitron Hearing, Kitchener, Ontario. Correspondence can be addressed to Donald Hayes, PhD, Unitron Hearing, 20 Beasley Drive, Kitchener, ON N2G 4X1, Canada; email: don.hayes@unitron.com.
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