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Use Spectrogram Analysis and Filtering to Hear Recorded Bat Noises More Clearly

by Audrey Trujillo

Recording of nighttime noises on Purdue's campus

In the above recording of my surroundings after dark on Purdue's busy campus, many different sounds can be heard. The crickets are chirping loudly, cars drive by, a man sings while riding by on his bike, and even the bell tower rings in the background at one point. Additionally bat chirps are heard faintly in the background. The plethora of other nighttime noises make the bat chirps quite difficult to hear however. Fortunately, we can use MATLAB to isolate these subtle chirps to hear them more clearly.

First, load the recording into MATLAB and produce a spectrogram of the original audio. Use this spectrogram to determine which frequencies the bat chirps occur at. As seen below in the spectrogram, there are two blue lines Spectrogram of recording of nighttime noises on Purdue's campus

MATLAB code used to filter recording of nighttime noises to hear bat noises more clearly Filtered recording of nighttime noises on Purdue's campus

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