Cochlear SPrint Sound Processor Informações Técnicas descarregar pdf (Página 34)

SECTION ONE | CLINICAL GUIDANCE

Figure 8 illustrates the electrical stimulation pattern of the English word

‘choice’ using a 6-channel CIS strategy. In this example, density of the

striations represents the rapid temporal changes in the signal. Since CIS always

stimulates the same channels, it does not convey frequency changes that

occur in the signal.

1.10 FREQUENCYTOCHANNEL ALLOCATIONS

Frequency-to-Channel Allocations

A primary function of the MAP is to translate the spectral information in the

incoming acoustic signal into instructions for channel stimulation. The electrodes

on the implanted array are numbered sequentially starting at the round

window. Electrode 1 is the most basal electrode and Electrode 22 is the most

apical electrode. Stimulation of different channels at identical stimulation rates

typically results in pitch percepts that reﬂect the tonotopic organization of the

cochlea. Channel 22 produces the lowest pitch percept while Channel 1 produces

the highest pitch percept. The frequency-to-channel allocation depends on the

sound processing strategy, the sound processor to be used and the number

of channels available for stimulation. During programming, Custom Sound

™

automatically assigns appropriate frequency-to-channel information.

The default table number for each sound processor (SPrint

™

, ESPrit

™

3G,

Freedom

™

, CP810), and for the ACE

™

, SPEAK and CIS strategies respectively,

is shown in the Custom Sound software. When converting between sound

processors, the default table is selected for the new sound processor. The table

numbering system for the CP810 and Freedom sound processors is that the

default table number is the same as the number of active channels in the MAP.

This differs from the SPrint and ESPrit 3G sound processors where a different

numbering system, not related to the number of channels, is used.

For the SPrint, Freedom and CP810 sound processors the default input frequency

range of 188-7938 Hz is maintained irrespective of the number of channels in

the MAP. However, if a non-default table number is chosen, the upper frequency

boundary reduces below 7938 Hz. In the case of 22 active channels, the available

non-defaults are Tables 1-5 for the SPrint and Tables 22 A-E for the

CP810/Freedom sound processors. In addition, when a CP810/Freedom

processor MAP contains less than 22 active channels, the higher numbered

tables are available and use of these tables progressively reduces the upper

frequency boundary. For example, when using the CP810/Freedom processor

with 20 active channels, the default is Table 20, however, Tables 21, 22, and 22A

- E are available. The default Table 20 provides the full input range of 188 - 7938

Hz, however, changing to Table 22 reduces the input range to 188 - 6063 Hz.

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