Estimation method

Parameter setting

Average error

Gradient

based method

(Variance of Gaussian differential filter)

(Differential filter’s size)

(Variance of Gaussian smoothing filter)

(Smoothing filter’s size)

0.96

Method based on orthogonal filtering

(center frequency)

(bandwidth)

(Number of filters)

0.35

Method based on regularized convolution

(Weight coefficients between odd and even filters)

(Filter size)

0.16

Method based on Gabor

(the ratio of Gaussian filter to Gabor filter)

n the number of filters

n = 3

error = 6

n = 6

error = 1.46

n = 10

error = 0.75

The method of this paper

(center frequency)

(Variance of filter)

n the number of filters

n = 3

error = 0.14

n = 4

error = 0.12