Lecture 22 Frequency Response Hung-yi Lee Filter Outline (Chapter 11) Amplitude Ratio Phase Shift...
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Lecture 22 Frequency Response Hung-yi Lee
Lecture 22 Frequency Response Hung-yi Lee Filter Outline (Chapter 11) Amplitude Ratio Phase Shift Highpass Filter Frequency Response Bode Plot Draw frequency
Filter Outline (Chapter 11) Amplitude Ratio Phase Shift
Highpass Filter Frequency Response Bode Plot Draw frequency
response Ch 11.4 Ch 11.1 Ch 11.2 Lowpass Filter Notch Filter
Bandpss Filter
Slide 4
Review Network Function Output depends on input and complex
frequency s.
Slide 5
Frequency Response Only focus on the change of frequency In
this lecture, we only focus on s=j. H(j) is the frequency response.
That is, only consider H(j)
Slide 6
Frequency Response H(j) is a complex number, so frequency
response is usually represented by two curves Magnitude Ratio Phase
Shift
Slide 7
Example 11.1 Network Function: Frequency Response:
Slide 8
Example 11.1 Based on Superposition:
Slide 9
Example 11.1 InputOutput
Slide 10
Example 11.2 Assume C=1/aR Find Network Function a=1/RC
Slide 11
Example 11.2 Set s=j The amplitude ratio is constant.
Slide 12
Example 11.2 Magnitude Ratio Phase Shift Distance of j to a
Distance of j to -a
Slide 13
Example 11.2 Phase shift network: Waveform distortion
Slide 14
Another Example for Phase Shift Network
Slide 15
Slide 16
Computing Frequency Response by Poles and Zeros
Slide 17
Frequency Response K: gain factor p 1, p 2, : poles z 1, z 2, :
zeros
Slide 18
Frequency Response - Magnitude Ratio Distance of j to z 1
Distance of j to p 1 Distance of j to p 2 Distance of j to z 2
Slide 19
Frequency Response - Magnitude Ratio Gain factor is K Magnitude
ratio at =| Gain factor| all distance to zeros all distance to
poles X
Range of Hearing Range of Audio: 300Hz 3.4KHz Frequency Range
of hearing: 20Hz - 20KHz dB
Slide 27
Equal Loudness Contour Red Curve: Equal loudness Blue Line:
Same Energy 60 phon means as loud as the 60dB 1kHz sound. phon
(unit): dB
Slide 28
Hearing v.s. Age Application: 68 ( )
Slide 29
Phase and Sound Pass a Phase shift network
Slide 30
Structure of Ear
Slide 31
Cochlea ( ) to brain Each neuron only passes a specific
frequency. Pass high frequency Pass low frequency Pass 20kHz Pass
20Hz
Slide 32
Cochlea ( ) to brain Neuron for =300 Neuron for =100 Neuron for
=20 =300, Amplitude=10 =20, Amplitude=10
Slide 33
Machine Hearing Each triangle is the amplitude ratio of a
filter How? Ear of machine A set of filters (filter bank) Energy of
the signal of the output of the filter Send to computer How to
write a program for speech recognition? a. Observe data, and write
down some rules b. Simulate human brain, and let the computer learn
by itself. Feature
Slide 34
Speech Signal ? ? Acoustic Model Language Model Text Machine
Learning Deep Neural Network (Brain) Features Speech Recognition
Signal Processing (Filter Bank)