I mounted a webcam on my backpack (facing backwards) and plugged a stereo mic into my laptop (held facing forwards). A Processing sketch acquires each frame and keeps a running sum of the last 256 frames. Every 32nd frame it saves the current average to disk. The audio is shrunk to size using SoundStretch.

The walk took 45 minutes: from West Hall at RPI, down the Approach, to Hill's art store, to Yo! Uncle Sam's Organic Food, into the Troy Library (very quiet), down River street, through a parking garage by the Hudson, Illium Cafe and over to 51 3rd.