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1 August 2011 Directional modalities Directional Microphone Technology in Oasis 14.0 and Applications for Use Directional microphones are among the most important features found on hearing instruments today. While the advantage of improving hearing in background noise is well documented, incorrect use of directional technology has consequences that may lead to user dissatis faction, time-consuming follow-up visits, or ultimately, the return of the devices. Bernafon s fitting software, Oasis offers directional microphone settings for each of your clients listening conditions, including Fixed Omnidirectional, Fixed Directional, Adaptive Directional, Adaptive High Frequency Directional, and True Directionality. Since individual customization is possible, the following information is a review of the main concepts behind the technology, to ensure proper utilization and maximum benefit. Fixed Omni For quiet environments. Available as a feature on all Bernafon family styles, the Fixed Omni microphone setting allows a hearing instrument to detect sound from all directions and angles around the user. Because an omnidirectional microphone is equally sensitive to all sounds regardless of the point of origin, it is best to use this technology in very quiet environments with little to no extraneous background noise which might compromise comfort and quality. Hearing Instrument is in an Omnidirectional mode This is the preferred setting for listening in quiet to: Television Music Speech in reverberant environments Speech at a distance Keep in mind that this mode detects environmental sounds occurring from behind the listener s head, important in some situations.

2 Fixed Directional For environments with constant noise across all frequencies. Available as a feature on all directional hearing instruments, Fixed Directionality provides the option for a full directional response across the entire frequency range of the hearing instrument. Here, the microphone response is most sensitive to signals from front-facing directions. Other sounds originating from the sides and behind the user are attenuated in a fixed hypercardioid polar pattern. Hearing Instrument is in a Fixed Directional mode For optimal noise control, acoustic signals are processed in four separate frequency bands. By this design, noise of different spectral characteristics can be attenuated more effectively based on its frequency content. For example, one band controls low-frequency noise, whereas three additional bands are dedicated to capturing noise falling in higher frequency ranges. To maximize benefit within the Fixed Directional setting, activate the Wind Noise Monitor and counsel the user on the following conditions: The desired speech source and background noise should come from different directions. The listener should be close (within 10 feet / 3 meters) to the signal.

3 Adaptive High Frequency For environments that fluctuate between quiet and noise. The Adaptive High Frequency Directional microphone mode constantly adjusts the polar pattern to minimize the level of the noise that is behind and to the side of the client even if the noise (or the client) is moving. Using a four-frequency band design, this mode responds with adaptive directional processing in the frequencies above 1000 Hz, while it remains omnidirectional in the low frequencies. Hearing Instrument is in the Adaptive High Frequency Directional mode By keeping low frequency signals audible, benefit occurs in the following areas: Important cues in the environment, often removed by the introduction of nulls (angles of maximum attenuation in the polar plot), remain perceptible. Wind and other near-field noises decrease. Speech intelligibility in reverberant environments is maintained. High frequency speech stimuli are identified immediately due to null steering (the ability to move the directionality to best attenuate the noise) in the upper three frequency bands.

4 Adaptive Directional For progressively noisier environments, Adaptive Directionality adjusts in the same way as the Adaptive High Frequency mode, described above, but it also fades to a full directional setting as environmental noise grows stronger. Hearing Instrument transitions between a 4 Band Full Directional mode and a Low Frequency Omni and High Frequency Directional mode When selected for an individual s listening program, this microphone setting engages between two directionality patterns, either (1) the Adaptive High Frequency Directionality mode or (2) a full directional mode, and automatically determines the most beneficial one required for the occasion. What occurs in each mode? The first mode responds with adaptive directional processing in the frequencies above 1000 Hz, while remaining omnidirectional in the low frequencies. In the second mode, there is null steering in all four frequency bands. How does this happen? A fast-acting adaptive mode selection algorithm reacts instantaneously to the microphone s detection of variations in sound pressure level, signal type (speech, noise), frequency content, and location in the environment. Seamlessly, it transitions between these two variable modes of directionality to provide the best signal-to-noise ratio as the auditory scene changes. For example, when noise levels increase, the system shifts toward full Directionality. As noise levels decrease, it changes smoothly and subtly back towards the Adaptive High Frequency response. Why is this important? With this approach, users maintain speech intelligibility in noise, especially as the noise levels increase. When conditions revert back to lower noise levels, they benefit from the known advantages of an omnidirectional response, which include improved comfort in quiet, windy, and reverberant environments.

5 True Directionality For BTE users only. Restoring proper sound localization and sound directivity is an important feature for today s growing population of BTE users. As such, Bernafon introduces the latest True Directionality microphone processing to address these specific needs. First, consider for a moment the nature of unaided ears, as well as those fitted with custom shell instruments with recessed microphone positioning. In these cases, localization of sound occurs normally from the front, back and sides, due to the way that sound waves travel around the body, head, and outer ear. Specifically, frequencies greater than 1000 Hz are collected from front-facing directions by the pinna naturally, whereas the lower frequencies bend and travel around the head and torso, entering the ear canal directly with negligible influence from the pinna (Kates, 2008). Now consider the nature of aided ears fitted with behind-the-ear instruments. Because the microphones of BTE instruments sit higher on the ear (compared to microphone placement on a CIC style for example), some of the natural characteristics of our inherent spatial localization abilities are lost, making it difficult at times for BTE users to know if the direction of sound is coming from the front or back (Best et al. 2010). True Directionality is a new feature designed to eliminate this source of confusion, by imitating the natural directivity index of the unaided ear, thereby preserving the manner in which low and high frequency sounds are initially propagated through the auditory system by head shadow effects and the shape of the external ear. A comparison of Bernafon s True Directionality directivity index compared to the open ear is illustrated in the curve beside:

6 True Directionality The directivity index (DI) describes how a sound originating from the front of an instrument compares to sounds arising from other locations around the instrument. When measured, the difference between an omnidirectional microphone versus a directional microphone placed in the same location in a sound field yields the DI value, expressed in db. A listener wearing an instrument with a higher DI will have a hearing advantage in noise since the response is more directionally focused. By matching this response to the open ear canal, BTE users experience the perception of sound naturally, like the unaided ear. At the same time, fixed directional polar patterns engage to capture high frequency speech stimuli in real time, restoring the missing cues needed for accuracy in localization, and further improving overall SNR. Default Directional settings As a reference, the following tables provide a short overview of which directional modalities act as the default setting for each available Bernafon listening program. BTE instruments Program Assignment Default Directional Setting Multi-environment True Directionality* Cinema Comfort in Loud Noise Adaptive Directional Conversation in Noise Fixed Directional Live Music Music at Home /TV Fixed Omni Conversation in a Car Telephone Telecoil/Microphone (Omni) Auditorium * True Directionality only available for Chronos 9 hearing instruments Custom instruments (equipped with directionality) Program Assignment Default Directional Setting Multi-environment Adaptive Directional Comfort in Loud Noise Conversation in Noise Fixed Directional Live Music Music at Home /TV Fixed Omni Conversation in a Car Telephone Auditorium Telecoil/Microphone (Omni) Cinema

7 Conclusions In summary, the microphone settings described above can be selected for directional hearing instruments available from Bernafon. The guidelines provide a rationale for choosing the appropriate microphone setting within four optional listening programs, based on the individual needs of the client. The information is intended to maximize the likelihood of obtaining the most effective signal-to-noise ratio in quiet and noise, thereby improving overall customer benefit and satisfaction with their hearing system. References Best, V.; Kalluri, S.; McLachlan, S.; Valentine, S.; Edwards, B; & Carlile, S. (2010). A comparison of CIC and BTE hearing aids for three-dimensional localization of speech, International Journal of Audiology, Vol. 49, No. 10: Kates, JM (2008). Digital Hearing Aids, San Diego, Plural Publishing, p. 55, 93 World Headquarters Switzerland Bernafon AG Morgenstrasse Bern Phone Fax Australia Bernafon Australia Pty. Ltd. 12/97 Castlemaine Street Milton QLD 4064 Freecall Phone Fax New Zealand Bernafon New Zealand Ltd. Level 1, Building F William Pickering Drive Albany, Auckland 0632 Toll Free Phone Fax United Kingdom Bernafon UK Cadzow Industrial Estate Off Low Waters Road Hamilton ML3 7QE Scotland Phone Fax Bernafon Companies Australia Canada Denmark Finland France Germany Italy Japan Korea Netherlands New Zealand Poland Sweden Switzerland UK USA 11.11/UK/BAG/subject to change