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A foreword by Mead Killion, Ph.D. Inventor of the Digi-K Technology, President of Etymotic Research
"Both the K-AMP and the Digi-K circuits were designed to be as high fidelity as we knew how to do. The Digi-K has a slight edge because of its ability to make fine adjustments to the frequency response to compensate for the transducers, but both received higher ratings in A-B listening-test comparisons than any other hearing aids. Just as important as the frequency response, however, is the ability to handle live performances by musicians without overloading. Both circuits had to pass our own listening tests with no sign of distortion: playing crashing fff chords on a 9' concert grand piano, playing high double stops on a powerful Ling violin, playing a trumpet, and singing loudly (106 dB SPL at the ear). Note: Many hearing aids have been designed to be free of distortion up to only 90-100 db SPL input. This is not good enough for live music. In order to handle the 104-106 dB I have occasionally clocked at live Chicago Symphony Orchestra performances, the hearing aid must be undistorted up to 115 dB SPL sine wave at the input because of the 10-15 dB peak factor in speech and music.
A final design consideration is the compression time constants. At least one well-known digital hearing aid advertised as "CD quality" had such a fast recovery time that recordings of a jazz piano trio made the brush-on-cymbol sound of swish-swish-swish sound instead like a nearly continuous shhhhhhhhhhhhhhhhh. The use of variable time constant "adaptive" compression virtually eliminates such defects.
A clear testament to the benefit of high-fidelity frequency response and the ability to handle high-intensity sounds is the fact that a couple years ago four members of the Chicago Symphony Orchestra wore K-AMP hearing aids on stage and off. They included a former concertmaster of the CSO, and the first chair of the second violin section.
A benefit unexpected by many was the demonstration that the ability to understand speech in multi-talker noise is directly proportional to fidelity. The highest fidelity hearing aids give the best intelligibility: No sacrifice is required." |
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Why Digi-K is the clear choice for musicians and audiophiles.
At General Hearing, from our founding over twenty years ago, we have relentlessly pursued the mission to bring high fidelity to the field of amplification. We have always believed that everyone, whether blessed with normal hearing or faced with hearing loss, can appreciate and will prefer smooth, broad-band sound.
To that end, the development of the DigiK has provided the platform upon which we can fulfill that goal on both a manufacturing and on a clinical fitting level. |
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On the manufacturing level, the DigiK offers a number of desirable features:
The Digi-K DSP hybrid has a 16 KHz. Bandwidth. When paired with wide band transducers, this enables us to provide a bandwidth rivaling stereo headphones.
The manufacturing software provides for electronic damping. Every microphone and receiver has resonant peak characteristics that impede the production of a smooth, wide-band, high-coherence response. Electronic damping makes it possible to eliminate those unwanted response peaks from the outgoing signal.
Following electronic damping, precise gain and output settings can be applied without being compromised by resonant characteristics of transducers
Most DSP hybrids are based on a “speech template”. As a result, incoming signals from the microphone are “clipped” before the digital signal processing occurs. This means that the outgoing signal can only be distortion-free at levels below 100 dBSPL. The DigiK design has eliminated peak input level limiting, providing expanded headroom without distortion secondary to input stage peak clipping. |
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On the clinical level, Digi-K provides an enormous amount of flexibility when programming:
Master controls allow for quick adjustments over wide-ranging parameters.
Three independent crossover frequency adjustments allow the professional to define the frequency response of each band.
For fine-tuning, there are four bands within which gain for soft sounds (as defined by the Threshold Knee setting on the Master Control page) and gain for loud sounds (90 dBSPL) can be independently programmed. This not only provides for precise gain and output levels within each band, it also provides control over compression ratios within each band. (Independent WDRC in each channel)
Memory designation ability allows specific programming for a wide range of listening situations
DigiK is clearly not the choice for every fitting situation. When there are concerns about feedback management or the like, the uncompromising design of DigiK may not be appropriate.
However, when high coherence and true fidelity are desired, Digi-K is the clear choice. |
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Electronic Damping Example
 The response of the hearing aid unequalized with peaks is automatically read from a hearing device analyzer. |
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 The filters automatically apply an inverse of the unequalized response. The grey line represents an unequalized response and the red is an equalizer response. |
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 The frequency response after removing the peaks and flattening the curve. |
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| 175 Brookhollow 504-733-3767 |  | New Orleans, LA 70123 |
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