Jane Greischer, age 11, of Hobart, Ind., for her question:

Do fish make a noise?

Not so long ago, people assumed that all was quiet beneath the ocean waves. They spoke of the mysterious and silent sea. Then marine scientists began to challenge this idea. They used. an instrument called the hydrophone, a sort of mechanical ear that listens to noises way below the surface of the sea and relays what it heard to human ears listening above the water.

The ocean depths turned out to be far from silent. In fact, we know now that the deep ocean is a very noisy place indeed. And the noises are made by all sorts of fish and other ocean dwellers. All the noises from below have not yet been identified, But a noise like galloping horses may be a school of moving fish or a convention of lobsters snapping their claws. Certain fish grunt and groan, others yap and bark.

Some squeak and squeal. A terrific racket, like machine gun fire, may turn out to be an army of snapping Shrimp doing their setting up exercises Even the porpoises, which are not really fish, make underwater noises. Through the hydrophone they sound lire a group of giggling girls.