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IEEE SIGNAL PROCESSING MAGAZINE [72] MARCH 2015

0.5

–0.5

6,400

3,200

Frequency (Hz)Magnitude + Electrode

1,600

800

400

200

100

Relative Magnitude

Frequency (Hz)Magnitude + Electrode Relative Magnitude

–1

0 0.05 0.1

Waveform MP3000 EE

0.15 0.2 0 0.05 0.1 0.15 0.2

0 0.05 0.1 0.15 0.2

ACESpectrogram F0mod

HiRes120CIS-22ch FSP

0 0.05 0.1 0.15 0.20 0.05 0.1 0.15 0.2

0 0.05 0.1 0.15 0.2

Time (s) Time (s) Time (s)

(g) (h) (i)

(d) (e) (f)

(a) (b) (c)

0 0.05 0.1 0.15 0.20 0.05 0.1 0.15 0.2 0 0.05 0.1 0.15 0.2

Synthesized Vowel ah

[FIG3]

(a) Waveform, (d) spectrogram, and (b)–(c) and (e)–(i) electrodograms for a synthesized vowel with F0=100Hz, and

formant frequencies 700, 1,220, and 2,600 Hz. The signal was presented at an average root-mean-square (RMS) level of

60dBsound pressure level (SPL). For the electrodograms, the vertical axis indicates the channel, and the height of each vertical

line represents the magnitude of the pulse. The magnitude is expressed in different units for different strategies. The red and

blue colors serve to visually distinguish adjacent channels and have no additional meaning. For the (g) CIS, (e) ACE, (b) MP3000,

(c) EE, and (f) F0mod strategies, the channel magnitudes are shown between 0 and 1 before compression. For (h) HiRes120, the

current was normalized by dividing by the maximum current, and normalized values below 0.1 were set to 0. HiRes120 uses

simultaneous stimulation of adjacent electrodes to generate virtual channels, which is hard to distinguish on the current plot.

For (i) FSP, the channel magnitudes between 0 and 1 are shown, which are linearly mapped to current, and multipulse sequences

have been replaced by single pulse sequences for clarity.

THE WORLD’S NEWSSTAND

THE WORLD’S NEWSSTAND