Filtering method For each frame(10-30 ms), a set of filter outputs will be calculated. frame overlap 5ms There are many different methods for setting the filter bandwidths --uniform or non-uniform Input waveform Time frame irms Filter outputs(v1, v2, Time frame i+-1 30ms Filter outputs(v'1, V2, Time frame i+2 Filter outputs(v"1,v"2 5ms Feature extraction v 9a
Filtering method • For each frame (10 - 30 ms), a set of filter outputs will be calculated. (frame overlap 5ms) • There are many different methods for setting the filter bandwidths -- uniform or non-uniform Feature extraction, v.9a 6 Time frame i Time frame i+1 Time frame i+2 Input waveform 30ms 30ms 30ms 5ms Filter outputs (v1,v2,…) Filter outputs (v’1,v’2,…) Filter outputs (v’’1,v’’2,…)
How to determine filter band ranges The pervious example of using 4 linear filters is too Simple and primItive. · We will discuss Uniform filter banks Log frequency banks Mel filter bands Feature extraction v 9a
How to determine filter band ranges • The pervious example of using 4 linear filters is too simple and primitive. • We will discuss – Uniform filter banks – Log frequency banks – Mel filter bands Feature extraction, v.9a 7
Uniform Filter banks · Uniform filter banks bandwidth B= Sampling Freq.(Fs)/no of banks(N) For example fs=10Kz n=20 then b=500HZ Simple to implement but not too useful FⅰterV1 output 123 4 5001K1.5K2K25K3K Feature extraction v ga
Uniform Filter Banks • Uniform filter banks – bandwidth B= Sampling Freq... (Fs)/no. of banks (N) – For example Fs=10Kz, N=20 then B=500Hz – Simple to implement but not too useful Feature extraction, v.9a 8 ... freq.. 1 2 3 4 5 .... Q 500 1K 1.5K 2K 2.5K 3K ... (Hz) V Filter output v1 v2 v3
Non-uniform filter banks: Log frequency ·Log.Freq… scale: close to human ear filter 1 filter 2 filter 3 filter 4 Center freq 300 600 1200 2400 bankwidth 200 400 800 1600 Filter output v1 v2 V3 200400800 1600 fre eq ..(HZ 3200 Feature extraction v 9a
Non-uniform filter banks: Log frequency • Log. Freq... scale : close to human ear filter 1 filter 2 filter 3 filter 4 Center freq. 300 600 1200 2400 bankwidth 200 400 800 1600 Feature extraction, v.9a 9 200 400 800 1600 3200 freq.. (Hz) v1 v2 v3 V Filter output
nner ear and the cochlea (human also has filter bands) Ear and cochlea 4000H2 Basilar membrane nergy Structure of ear 3000+ 800 utricle saccule semicircular N canal inner 1000H cochlea 2000H2 7000 出mk middle ossicles ound energy Oval wind eustachian tube \canal Round auricle external 20000H2 http:/universe-review.ca/110-85-cochlea2.ipgFeatureextractionv.9a http://www.edu.ipagojp/chiyo/hubed/html1/en/3d/ear.html
Inner ear and the cochlea (human also has filter bands) • Ear and cochlea http://universe-review.ca/I10-85-cochlea2.jpg Feature extraction, v.9a 10 http://www.edu.ipa.go.jp/chiyo/HuBEd/HTML1/en/3D/ear.html