A common example of an impulse sound is:

An impulse sound is characterized by a short-duration, high-intensity sound that occurs suddenly and is typically followed by a quick decay in sound pressure. A pile driver is a perfect example of this type of sound, as it generates a powerful, brief auditory impact when the hammer strikes the pile, providing significant energy in a very short time span.

In contrast, the other options represent different categories of sounds. A radio playing is generally a continuous sound with varying frequencies and amplitudes. A soft whisper is a low-level sound that is also continuous in nature, lacking the sharp intensity associated with impulse sounds. Finally, a continuous alarm produces a steady sound over time rather than the brief, sharp peaks characterizing impulse sounds. Hence, a pile driver exemplifies an impulse sound due to its sudden, abrupt nature and high intensity.