Ask-the-Expert
With regard to advanced hearing aid technology, please explain the term Voice Priority Processing?
A: Voice Priority Processing refers to the coordination of signal processing in Syncro. It uses a parallel processing, Artificial Intelligence-based digital circuit design to ensure that features such as Multi-band Adaptive Directionality, TriState Noise Reduction and Voiced Aligned Compression are all simultaneously optimized to, first and foremost, ensure the best possible treatment of the speech signal. With regard to advanced hearing aid technology, what does Artificial Intelligence mean?
A: Artificial Intelligence makes use of parallel processing in the circuitry of products such as Syncro, Safran and Tego to do the type of signal processing that is not possible in analog products or digital products that only use serial processing. It allows multiple tasks to be completed at the same time, optimizing the amount of signal processing that can occur in real-time. In our products, we use Artificial Intelligence to perform off-line but real-time analysis of all potential combination of settings within our products. The system can then take the optimal combination of processing for that sound environment for that moment in time. I know the term Fusion Fitting has been associated with open ear fittings. What makes fusion fittings unique?
A: The term Fusion Fitting refers to the situation in which the hearing aid user hears both sounds processed by the hearing aid but also direct sound entering the ear canal. Of the we believe that the picture of these two sound sources especially in the high frequencies can help improve both performance and perceived sound quality especially in more challenging environments. Please explain the benefits of THIN TUBE hearing aid fittings, such as Corda?
A: Thin Tube fittings have the basic advantage of being more cosmetically acceptable for the patient. The width and texture of thin tubes make them far less noticeable. In addition, thin tubes allow for the use of open domes in the air canal. As long as there is no more than a mild hearing loss in the low frequencies, open domes are far more acceptable in terms of comfort and sound quality for patients. What is the difference between wide dynamic range compression and multi channel non-linear amplification?
A: For all practical purposes, these two terms refer to the same design of modern compression systems in hearing aids. Essentially all hearing aid approaches designed for sensorineural hearing loss use wide dynamic range compression. What this means is that a broad range of input levels, typically from 40 dB through 80 dB SPL, are compressed using moderate ratios in the range of no more than 3:1. In addition, essentially all modern hearing aids also use compression in multiple channels in order to keep sounds in one frequency region from unduly affecting the gain and compression applied to sounds and other regions. Probably the most accurate and all-encompassing term would be multi-channel, wide dynamic range compression.
Please review the benefits of receiver-in-the-ear (RITE) technology?
A: For BTE hearing aids, when the receiver is placed over the ear, the sound is forced through a long narrow tube. This is an inefficient and unnatural way to transfer sound from one place to another. This tubing will create resonant peaks and dips in the higher frequencies that can negatively affect sound quality. When the receiver is placed in the ear canal, these irregularities in the frequency response are not created. With the standard receiver placement over the ear, the electronics of the hearing aid are used to try to correct for the irregularities. With the RITE approach, this electronic flexibility can be reserved for more appropriate uses such as maximizing the high frequency response of the device or making fine adjustments to maximize sound quality.
Why is it that audiologists fit children with FM systems to improve the signal-to-noise ratio (while limiting the range of inputs to the auditory system, i.e., the input is limited to the FM microphone), yet some audiologists are reluctant to fit advanced technology hearing aid systems with adaptive directionality and noise management systems on children?
A: Audiologists who fit hearing aids to children often want to make sure that all available speech information is provided to the child. There is concern by some professionals that advanced signal processing approaches that are appropriate for adults may somehow reduce the amount of information that is provided to the child. This is a valid concern. In older versions of automatic directionality and noise reduction, there were situations in which the signal processing did reduce the amount of speech information provided to the user. These systems have evolved over the last few years and have paid closer attention to protecting the content of speech. It is important for the audiologist to understand how the specific systems in the hearing aids being selected for the child are working. From manufacturer to manufacture, the system was will vary. Some will do a better job of protecting the speech signal than others. The better that the audiologist understands how these systems work in the specific hearing aids that he/she is using, the more confident he/she can be in recommending the specific approaches for children.
I have read that noise reduction systems don't actually reduce noise. Please tell me what is it that they do?
A: It depends on what you mean by "reduce noise". Noise reduction systems in modern hearing aids can do one thing: reduce gain in frequency regions that are dominated by noise. They do reduce noise, however they also reduce any speech information that would be in that same frequency region. Therefore they do not improve the signal-to-noise ratio. When the systems do reduce again applied to frequency regions that seemed to be dominated by noise, the result for the listener is a signal that is less fatiguing to listen to. The listener may report that noise has been reduced, however, except extremely rare situations, you would not expect to see improvement in speech understanding and noise.
Please explain the differences between directionality, automatic directionality and automatic adaptive directionality?
A: Directionality refers to systems used in hearing aids to reduce the sensitivity to sounds arising from directions other than in front of the listener. Automatic directionality describes how the hearing aid transits between at omni and directional setting. Previous generations of directional hearing aids were controlled by a manual switch or remote-control. The user decided when the hearing aid was in omni or directional. An automatic systems some decision making paradigm with in the product will decide whether or not the device should be in omni or directional setting. These decision making approach is very significantly from manufacturer to manufacturer. Adaptive directionality refers to the shape of the polar plot (the sensitivity pattern of the hearing aid) when the hearing aid is in directional. Most modern automatic directional systems also will vary the polar plot depending on the environmental conditions. Please tell me the advantages of multi-band adaptive directionality?
A: Up until a couple years ago, all directional systems operated across the entire bandwidth of the hearing aid. With the release of Oticon Syncro, you started to see hearing aids that had independent directional systems and different frequency regions. This allows for two benefits. First, it allows the shape of the polar plot to vary depending on the frequency content of the noise in the environment. In situations in which there are distinct spectral differences between noises that arise from different locations in the room, the hearing aid can optimally cancel sounds from different directions. Secondly, the way we implement multi-band directionality and Oticon products is unique in that, under certain circumstances, we will keep the hearing aid and omni in the low frequencies and directional and a higher frequencies. This allows for the signal-to-noise racial improvements in the higher frequencies but without the negative sound quality in the implications when a system goes into directional in the low frequencies in moderate sound environments.
In the Delta hearing aid, what are the different "dome" types and fitting ranges, and can you please tell me what happens when you use custom-made earmold?
A: The original release of Delta was targeted for patients with high frequency hearing loss. With the release of Delta XR in December of 2006, we have extended the application of Delta to patients with hearing loss in any frequency region up to 80 dB HL. For patients with hearing loss only in the high frequencies, we recommend the use of Dome coupling in order to keep your canal as open as possible. However, when the hearing losses 30 dB or greater in the low frequencies, we recommend using either a closed Dome (we call it the Plus Dome) or a custom ear mold. These allow for better retention of low-frequency sound which is essential for patients with low-frequency hearing loss. Professionals can order custom your molds called Micro Molds from us. They can also order custom ear molds from their preferred ear mold supplier. We also offer to fitting rationales in Delta. The Clarity rationale is targeted towards patients with high frequency hearing loss. The Voice Aligned Compression rationale is appropriate for patients with hearing loss across the audiogram.
Regarding directional microphones, which situations are ideal, and in which situations do you expect to added benefit?
A: Over the past few years, we have learned more about the effectiveness of directionality in hearing aids. It is clear that directional hearing aids can directly improve the signal-to-noise ratio under certain circumstances. However, if the conditions are not right, it appears that patients would prefer that directionality is not active. The conditions under which directionality is indicated are as follows: the talker must be in front of the listener, the listener must be facing the talker, the talker must be reasonably close to the listener (typically within one to three meters), there must be noise present and that noise must originate from locations other than directly behind the talker. Under those conditions directional microphones will improve the signal-to-noise ratio and patients will perform better. However if those conditions are not met, directionality will not improve performance and, importantly, patients will prefer the sound quality of an omni-directional setting.
Regarding compression release times..what are the advantages and disadvantages of slow versus fast release times?
A: the release time of the compression system and hearing a will affect how much sound energy is packed into their dynamic range of the listener. Most professionals assume that if more speech energy is presented the patient, speech understanding should improve. A fast release time will minimize the phone in the phoneme intensity differences in speech, allowing for more speech sounds to be audible to the patient. However, for some patients, especially those who start to exhibit cognitive declines, a fast acting system may simply provide too much information. The patient's cognitive system becomes overloaded and information is lost. A slower release time maintains more than natural intensity differences between phonemes. Not as much speech energy can be placed within the patient's dynamic range. However, information that is available may be easier to process. Patient age is a modest predictor of cognitive deficiency. Therefore, we typically recommend slower release times for patients in the seventies and beyond. There are also some patients who simply prefer the sound quality of compression system with a slower release time. In most of our nonlinear products, we offer options to modify release time. Please explain Tri-State Noise Management?
A: Tristate Noise Management is a signal processing routine in Syncro and Delta 8000 designed to reduce the annoyance of noise in the environment at the same time as protecting frequency regions that contain important speech information. This system uses two separate analyses of the incoming signal. On a channel by channel basis, the modulation characteristics of the signal are evaluated to identify frequency regions that are dominated by noise. At the same time, the high frequency region is monitored, looking for the evidence of a harmonically related signal in the environment. Speech and music are the two most common harmonically related signals with energy in the region from 1000 to 8000 Hz. The amount of noise reduction specified by the modulation analysis is tempered during times in which the second, synchrony analysis system has identified the presence of speech in the environment. This combine noise reduction system allows for channel by channel reductions when called for, but also is extremely sensitive to the presence or absence of speech. We believe this is the best approach to achieve the benefits of modulation based noise reduction without threatening the information content of the signal. If you would like to ask a question, please contact:
Douglas L. Beck Au.D.
Director of Professional Relations, Oticon Inc.
dmb@oticonusa.com
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