The sperm whale's head holds the spermaceti organ and a fatty structure called the junk, arranged around a nasal passage. Air forced through a pair of lips near the front of the snout, the museau de singe, produces a sharp pulse. That pulse reflects backward through the spermaceti, off an air sac against the skull, and is then focused forward through the junk as a narrow beam.
Because the sound is beamed, on-axis measurements are extreme. Recordings from arrays placed in front of hunting whales have logged source levels above 230 decibels relative to one micropascal at one metre, peak to peak. Decibels in water are referenced differently from decibels in air, so the figure cannot be compared directly with a jet engine.
The clicks are a sonar for finding squid, not a weapon. The recurring claim that sperm whales stun prey with sound has never been demonstrated, and stomach contents routinely include intact, unharmed squid.