Cochlear SPrint Sound Processor Informações Técnicas descarregar pdf (Página 68)

SECTION TWO | CLINICAL GUIDANCE

2.1.1.4 Fine Tuning the ABI

Balancing/sweeping

Before carrying out any pitch perception test, it is important to balance the

loudness of all functional channels. To achieve this, ﬁrst balance at C-level, and

then at 50% of the dynamic range.

• Balancing at C-level – Use the Sweep option to stimulate pairs/groups

of channels at C-level, making adjustments as appropriate. Always use one

balanced channel as a reference for the next one. Do not balance channels

with reduced loudness due to a side effect but, instead, balance other

electrodes and then consider omitting this electrode from the ﬁnal MAP.

This is particularly relevant if, after pitch ranking, this electrode falls into

the more useful frequency range, below 4 kHz.

• Balancing at 50% of dynamic range – Carry out loudness balancing

at 50% of the T-C range and then adjust the T-level to compensate, e.g.

reduce the T-level for any channel that sounds louder than its neighbour.

Pitch-ranking

Unlike the cochlear implant electrode array, it cannot be assumed that there is a

deﬁnite tonotopicity across the auditory brainstem implant electrode array. This

makes it essential to pitch rank all functional channels before creating a MAP.

Pitch ranking is generally quite difﬁcult for Nucleus 24 ABI recipient because:

• most recipients report a mixed or complex pitch percept on each

channel in response to stimulation and these are difﬁcult to compare

with one another

• many channels may sound quite similar in overall pitch

• changing the stimulus intensity may change the pitch percept on

an individual channel

Use the Nucleus 24 ABI Pitch Ranking Worksheet (Figure 9) to compare

successive electrode pairs.

Tip: Use the Set Levels screen to present stimuli. Deactivate all channels except

the two that require comparing and then use the sweep or balance option.

N33595F ISS3 FEB10

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