Squirrels DO make noise.
More Info: Squirrels not only make noise, they have their own communication system. Special squirrel noises warn other squirrels about danger, scare away predators and enable baby squirrels to call their mothers. Males use them as mating calls in early winter.
Categories of Squirrel Talk
Robert Lishak PhD, a biology professor at Auburn University, says that squirrels communicate with four main sounds:
Kuk: a bark-like warning to an approaching enemy
Quaa: a long kuk, a loud meow, when the threat is abating
Quaa moan: a chirp followed by a meow to signal that the enemy is leaving
Muk-muk, like a small sneeze; it has two meanings: a sound from baby squirrels when they are hungry, and a male mating call
To classify and quantify the squirrel vocalizations, Lishak and his students recorded the squirrels in the field, sometimes using a model of a cat, or a real trained cat, to elicit squirrel speech. To verify their classifications, They then returned to the laboratory to analyze the recordings by creating spectrograms. Playing the recordings in a spectrograph machine visually measured and compared the sounds’ duration and frequency, represented by rising and falling jagged lines Through those images and sounds the spectrograms confirmed Lishak’s kuk, quaa, quaa moan and muk-muk.
Washington Post interview with Dr. Lishak, April 10. 2012 http://www.washingtonpost.com/local/learn-to-speak-squirrel-in-four-easy-lessons/2012/04/09/gIQAV8Jr6S_story.html
Reprint of Lishak paper, Alarm Vocalizations of Gray Squirrels, Journal of Mammalogy, November 1984 http://www.jstor.org/discover/10.2307/1380852?uid=3739776&uid=2129&uid=2&uid=70&uid=4&uid=3739256&sid=21101216041133