Cochlear SPrint Sound Processor Información técnica descargar pdf (Pagina 43)

CLINICAL GUIDANCE | SECTION ONE

The polar plots in Figure 14 compare the directional sensitivity of Beam (light

blue line) and a ﬁxed directional microphone (dark blue line) for noises coming

from different directions. On the plots, 0° corresponds to in front of the listener,

90° to the left, 180° behind and 270° to the right. In the ﬁrst plot, a noise

source is placed at 90° (indicated by the large arrow) that corresponds to the

left side of the recipient. Unlike the ﬁxed directional microphone pattern, Beam

signiﬁcantly reduces the sensitivity of the processor, as indicated by the ‘notch’

shape of the pattern at 90° on the plot. The remaining plots similarly show how

Beam responds to noise sources at 120° and 180°. In each case, the standard

directional microphone plot is ﬁxed, while the Beam pattern changes to reduce

the processor’s sensitivity in the direction of the noise source.

The second stage of the algorithm, the adaptive noise canceller, serves to

ﬁlter out the noise from the beamformed signal. Since it is an adaptive ﬁlter, it

adapts to the changing noise environment, producing an optimal beamformer

output. This adaptation only occurs if speech has not been detected in

the signal, thereby minimizing distortion on the speech component of the

beamformed signal. Since the adaptive noise canceller effectively moves the

nulls in the beamformer output toward the interfering noise signal, the overall

algorithm is called ‘adaptive beamformer’.

Figure 14: Examples

of sensitivity plots

for Beam (light

blue line) and a

ﬁxed directional

microphone (dark

blue line)

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Cochlear SPrint Sound Processor Información técnica Pagina 43