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Robustness Techniques for Feature Extraction - Berlin Chen

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Spectral Subtraction (SS)<br />

• Modification: Nonlinear Spectral Subtraction (NSS)<br />

Pˆ<br />

P<br />

S<br />

⎧PX<br />

( ω ) − PN<br />

( ω ),<br />

if PX<br />

( ω ) ≥ PN<br />

( ω )<br />

( ω ) = ⎨<br />

⎩PN<br />

( ω ),<br />

otherwise<br />

( ω ) and P ( ω ): smoothed noisy and noise spectrum<br />

X<br />

N<br />

or<br />

Pˆ<br />

P<br />

φ<br />

⎧P<br />

( ) ( ) ( ) ( ) ( )<br />

X<br />

ω − φ ω , if PX<br />

ω > φ ω + β ⋅ PN<br />

ω<br />

( )<br />

S<br />

ω = ⎨<br />

⎩β<br />

⋅ P ( ω )<br />

N<br />

, otherwise<br />

( ω ) and P ( ω )<br />

X<br />

N<br />

: smoothed noisy and noise<br />

( ω ):<br />

a non - linear function according to SNR<br />

spectrum<br />

16

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