Ever notice how quiet it gets after you turn off your computer? When the power is on, your computer's internal components vibrate the case of the computer, causing irritating noise.
Faster computer processors generate more heat, which means more fans must be installed in the case to control heat and protect sensitive components. These extra fans also contribute to increased noise. Many computer manufacturers have recognized the noise problem and are beginning to develop quieter components; however, even quiet components emit noise and cause case vibration.