How do they function, having such small eyes and ears?
Here is a useful article:
"... In 1839, in the first scientific treatise on the sperm whale, Thomas Beale, a surgeon aboard a whaler, wrote that it was “one of the most noiseless of marine animals.” While they do not sing elaborate songs, like humpbacks or belugas, in fact they are not silent. Whalers in the 1800s spoke of hearing loud knocking, almost like hammering on a ship’s hull, whenever sperm whales were present. They called the animals “the carpenter fish.” Only in 1957 did two scientists from the Woods Hole Oceanographic Institution confirm the sailors’ observations. Aboard a research vessel, the Atlantis, they approached five sperm whales, shut off the ship’s motors and listened with an underwater receiver. At first, they assumed the “muffled, smashing noise” they heard came from somewhere on the ship. Then they determined the sounds were coming from the whales.
Biologists now believe that the sperm whale’s massive head functions like a powerful telegraph machine, emitting pulses of sound in distinct patterns. At the front of the head are the spermaceti organ, a cavity that contains the bulk of the whale’s spermaceti, and a mass of oil-saturated fatty tissue called the junk. Two long nasal passages branch away from the bony nares of the skull, twining around the spermaceti organ and the junk. The left nasal passage runs directly to the blowhole at the top of the whale’s head. But the other twists and turns, flattens and broadens, forming a number of air-filled sacs capable of reflecting sound. Near the front of the head sit a pair of clappers called “monkey lips.”
Sound generation is a complex process. To make its clicking sounds, a whale forces air through the right nasal passage to the monkey lips, which clap shut. The resulting click! bounces off one air-filled sac and travels back through the spermaceti organ to another sac nestled against the skull. From there, the click is sent forward, through the junk, and amplified out into the watery world. Sperm whales may be able to manipulate the shape of both the spermaceti organ and the junk, possibly allowing them to aim their clicks. The substance that made them so valuable to whalers is now understood to play an important role in communication..."
"... “Acoustics is a great way to see what’s going on where you can’t see,” Benoit-Bird says. To understand sperm whale sound, she had to first establish how the whales use their clicks to find squid. Unlike fish, squid don’t have swim bladders, those hard, air-filled structures that echolocating hunters such as spinner dolphins and harbor porpoises typically key in on. “Everyone thought squid were lousy sonar targets,” she says. But she thought it unlikely that the whales would spend so much time and energy—diving hundreds or thousands of feet, clicking all the way down—only to grope blindly in the dark.
In a test, Benoit-Bird, Gilly and colleagues tethered a live jumbo squid a few feet under their boat to see if the echo sounders could detect it. They found that squid make fabulous acoustic targets. “They have plenty of hard structures for sonar to pick up,” she says. Toothy suckers cover their arms; the beak is hard and sharp; and the pen, a feather-shaped structure, supports the head. Benoit-Bird was thrilled. “You could say,” she says, “that I’m learning to see like a sperm whale.”..."
An illustration from Cosmos Magazine: