Massachusetts Institute of Technology Department of Electrical Engineering and Computer Science 6.341:DISCRETE-TIME SIGNAL PROCESSING OpenCourse Ware 2006 Lecture 21 Short-Time Fourier Analysis Reading:Sections 10.1-10.5 in Oppenheim,Schafer Buck (OSB). In the discussion of spectral analysis of deterministic signals,the signal is usually processed by a system as shown in OSB Figure 10.1,where the DFT is applied,possibly with windowing to satisfy its finite-length requirement.In OSB Figure 10.2 are Fourier transforms associated with this system. While the output of this system represents the active signal,in more complex signals such as speech or music where the signal properties change over time,it is clearly more meaningful to refer to the changing frequency content over a smaller time interval rather than over an infinite time interval.The next figure is an example of a speech waveform that possesses high spectral locality in time: 200msec 4 Example of a speech waveform illustrating different classes of sounds. The utterance is "should we chase ...(Reproduced from Chapter 3. A.V.Oppenheim,Applications of Digital Signal Processing.) 1Massachusetts Institute of Technology Department of Electrical Engineering and Computer Science 6.341: Discrete-Time Signal Processing OpenCourseWare 2006 Lecture 21 Short-Time Fourier Analysis Reading: Sections 10.1 - 10.5 in Oppenheim, Schafer & Buck (OSB). In the discussion of spectral analysis of deterministic signals, the signal is usually processed by a system as shown in OSB Figure 10.1, where the DFT is applied, possibly with windowing to satisfy its finite-length requirement. In OSB Figure 10.2 are Fourier transforms associated with this system. While the output of this system represents the active signal, in more complex signals such as speech or music where the signal properties change over time, it is clearly more meaningful to refer to the changing frequency content over a smaller time interval rather than over an infinite time interval. The next figure is an example of a speech waveform that possesses high spectral locality in time: Example of a speech waveform illustrating different classes of sounds. The utterance is “should we chase ...” (Reproduced from Chapter 3, A.V. Oppenheim, Applications of Digital Signal Processing.) 1