The phrase "faint sound" means a very soft or quiet noise that is difficult to hear.
Sentences with «faint sound»
Listening closely, you hear faint sounds of the city awakening across the Nile. (sofitel.com)
Since it is a moving noise and happens at a relatively high speed it will probably be a very faint sound when the car is on blocks (and may not occur at all if it requires a loaded suspension). (mechanics.stackexchange.com)
On the chip's surface, which is cooled to near absolute zero -LRB--- 459 degrees Fahrenheit) to eliminate thermal vibrations, two tiny aluminum cones connected by an electric field generate extremely faint sound waves that bounce back and forth. (discovermagazine.com)