More on the Spectrograms

In the last post we discussed how we were able to plot spectrograms using the spectrogram module in ObsPy. A few days ago, we were able to to show some of those plots to Dr. Monica Kohler. Our plots seemed very pixelated as compared to the plots that she normally used. We were looking for a way to plot spectrograms of good resolution and palpable color distribution within different intensities for the Los Angleles Department for Water and Power (LADWP) multi-storeyed building. Following plot can be considered a perfect example for the scenario.

Spectrogram plotted by Ming Hei, a graduate student, for the Millikan Tower, a multistory Building at Caltech. Make note of intense horizontal lines, which refer to harmonics of the building.

Dr. Kohler offered few suggestions that could help us improve our plots-

1. To apply a 2 pass 2-pole Butter-worth Bandpass filter for 0.1 to 20 Hz before calculating spectrograms
2. To change the color scheme such that maximum spectral amplitudes appear as bright red (see spectrogram above)

We will try to incorporate these suggestions.