Basics of MATLAB and Beyond

the periodograms of the blocks, and averages the periodograms at eachfrequency. This is a technique commonly used to reduce the varianceof the PSD. For example, we can compare the variance of the aboveestimate to that of a single periodogram by telling spectrum to use ablocklength equal to the length of the signal:spectrum(y,8192)You can also specify windows to reduce spectral leakage, sampling frequenciesto get correct frequency scales and overlapping blocks. If youare interested in PSD estimation, the Signal Processing toolbox containsother methods of PSD estimation including Welch’s method, MUSIC,maximum entropy and multitaper. matlab also provides a graphicaluser interface for spectral estimation as part of its interactive signal processingenvironment sptool. The System Identification toolbox also containsalgorithms for PSD estimation (type iddemo and choose option 5for a demonstration).19 Sounds in MATLABmatlab can send data to your computer’s speaker, allowing you to visuallymanipulate your data, and listen to it at the same time. A digitisedrecording of an interesting sound is contained in the mat-file chirp.mat.Load this data, do a plot, and listen to the sound by typing:load chirpplot(y)sound(y)The volume of the sound can be controlled from within matlab usingthe soundsc function and supplying an upper and lower limit. Or ifyou wish, you can use your computer’s system software to control thevolume. On UNIX the volume of the sound can be controlled with thec○ 2000 by CRC Press LLC