User's Manual - Cornell Lab of Ornithology - Cornell University

Chapter 3: Spectrum Analysiswill reveal structural details of the signal that are invisible in a boxy lowresolutionspectrogram (Figure 3.16). Smoothed spectrograms take longer toredraw than boxy spectrograms.(a)(b)(c)Figure 3.16. Difference between smooth-style display of spectrogramcalculated on low-resolution grid and boxy display calculated on a higherresolutiongrid. The signal is one syllable from an American robin song,digitized at 22.3 kHz. In all three spectrograms, filter bandwidth = 352.9 Hz(frame length = 256 points = 11.5 mS), window = Hamming. (a) Boxyspectrogram on low-resolution grid: 11.5 mS x 86.9 Hz (frame overlap = 0%,FFT size = 256 points). (b) Same spectrogram as (a), but with smooth display.(c) Boxy spectrogram with higher-resolution grid: 1.4 mS x 21.7 Hz (frameoverlap = 87.5%, FFT size = 1024 points). Notice the rapid frequencymodulation about halfway through the syllable that is detectable in (c) but notin (a) or (b).Once a spectrogram has been calculated, you can switch back and forthbetween boxy and smooth displays without recalculating the entirespectrogram. Typing Command-G or option-clicking on the command panel’sSPG button will bring up the spectrogram dialog box. If you change thedisplay style without changing any other parameters, the spectrogram isimmediately redrawn in the selected style.62 Canary 1.2 User’s Manual