unwarping

scale

quency axis in a way that is most tolerable by our ears. The procedure consists

in transforming the desired frequency response according to (53), and designing

a digital filter that approximates it using some filter design method [65]. Then

the inverse conformal mapping (unwarping) is applied on the resulting digital

filter. Some filter design techniques, beyond giving a better approximation in a

psychoacoustic sense, take advantage of the expansion of low frequencies induced

by the warping map, because low-frequency sharp transitions get smoother and

the design algorithms become less sensitive to numerical errors.

13500, 20500, 27000