Alera FAQs – DFS Ultra Part 2

If it is suspected that a fitting may be unstable, what are some possible causes?
Gain in the Aventa software is set too high; the incorrect model of hearing instrument may have been chosen for that person (e.g., custom instrument chosen over BTE solution); the custom hearing instrument shell or BTE earmold does not fit properly; an incorrect style of earmold was chosen; the custom hearing instrument or BTE earmold is too large; or the patient is not properly inserting the hearing instrument and/or earmold.

Why do dispensers experience feedback earlier than expected, sometimes even before the G50 curve reaches the maximum stable gain?  And what can they do to achieve more maximum stable gain?
If a dispenser experiences feedback before expected, apply the following steps in order to help achieve more maximum stable gain and ensure the feedback is not caused by other influences.
a.    Confirm all standard acoustic measures have been considered, such as appropriate instrument selection, appropriate configuration of the device (i.e. open or closed, thin tube or standard tube) proper and secure fit and any other acoustic measures that can increase the risk of feedback.
b.    If the instrument is an RIE, confirm that the actual receiver matches how the device is configured in the Aventa3 software
c.    Re-run the DFS calibration.
d.    Increase DFS Ultra setting (proceed one step at a time, until feedback is eliminated).

Is there any performance indicator of DFS Ultra or occurrence of feedback in data logging?
No. Dispensers need to rely on subjective input from patients.

Is Whistle Control a notch filter approach?
No. The algorithm tunes the gain reduction to the frequency area where feedback is going to occur. The amount of gain reduction and frequency area where it occurs is dynamic and depends on the individual fitting and situation. It is not pre-configured like a notch filter.

Is it true the impact of DFS Ultra/Whistle Control does not reduce gain below the preferred frequency response?
Yes, except in some situations where the “strong” setting may reduce the gain a few dB below the preferred frequency response.

How fast does DFS Ultra/Whistle Control react when feedback is noticed?
It reacts instantaneously, as it is constantly monitoring for “leftover” feedback. It adjusts the gain so that this unwanted signal does not continue.

How does the display of the MSG in Aventa 3 relate to the green MSG display in Aventa 2?
The dark grey curve is above the full on gain of the instrument.  The light grey curve appears once the device is calibrated.  The lower edge of the light grey is the MSG for the individual without DFS Ultra.  Feedback risks are very low if the gain curves are below the MSG curve (light grey).   If gain is increased into the light grey area, risks for feedback also increase.  If “safe fitting” is enabled, the dark grey area will be lowered into the light grey area.  This represents the maximum gain for a feedback-free fitting with DFS Ultra active, and corresponds to the top of the green MSG curve that is displayed in Aventa 2.

What are the improvements with DFS Ultra?
DFS Ultra incorporates a signal model in addition to a model of the feedback path.  This improves how robust the system is to tonal signals, meaning the DFS Ultra is very unlikely to try and cancel external sounds that are not feedback.  Thus, the main improvement for the user is better sound quality and more stable performance for all fittings.  With legacy technology, sound quality could suffer in fittings where the gain is high relative to the MSG.  The benefit for DFS Ultra will be most obvious for open fittings.

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