How can noise be good?
Another example is setting up A/D converters - usually the input is set so that the noise just trips the least significant bit (LSB) of the converter. The noise can also be added manually - this process is also referred to as Dithering. The white papers at various A/D manufacturers can be quite useful e.g. Linear Technologies, Analog Devices and Texas Instruments.

Another term you may wish to look under is Stochastic Resonance.