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CLINICAL GUIDANCE | SECTION ONE

1.9.2 SPEAK

SPEAK (Spectral Peak) focuses on the spectral (frequency) properties of

sound. It takes advantage of the 22 closely spaced intracochlear electrodes

and the place pitch selectivity of the cochlea. The sound processor examines

the ongoing acoustic signal and sends stimulation pulses to the appropriate

electrode sites or channels based on the signal’s spectral content. The places

of stimulation in the cochlea vary depending upon ongoing spectral analysis.

SPEAK needs a large number of intracochlear electrodes to take advantage of

the cochlea’s spectral selectivity. SPEAK continuously analyses the energy in

sound and determines the spectral maxima. These are the frequency regions in

the signal that have the largest amounts of energy.

SPEAK divides the acoustic bandwidth (188 – 7938 Hz) into 20 bands and

assigns each active channel to one of these frequency bands in a tonotopic

way (i.e. the most basal channel receives the highest frequencies and the most

apical channel the lowest frequencies). After SPEAK identiﬁes the maxima, the

channels that correspond to the correct frequency bands receive stimulation

pulses. The amount of electrical current (between T- and C-level) sent to the

channels is directly proportional to the amount of energy in the frequency

bands. As the acoustic signal changes, the maxima and the stimulated

channels vary across the array. SPEAK uses a maximum of 20 bandwidths, so

20 of the 22 possible channels can be used as active sites. By default, for each

stimulation cycle SPEAK identiﬁes eight maxima and delivers stimulation to the

selected channels. The channels that are selected vary as the sound changes.

The clinician can increase the number of maxima up to 10.

Figure 5 :

Electrodogram of

the English word

“choice” using the

ACE strategy

1 2 ... 26 27 28 29 30 31 32 33 34 35 36 ... 77 78

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Cochlear SPrint Sound Processor Informazioni Techniche Pagina 31