Barbara Piper, age 11, of Utica, New York, for her question:
Can any animal hear above 80,000 cycles per second?
Healthy human ears can hear sounds as high as 20,000 cycles per second, and a very good ear can hear somewhat higher sounds. 'lost animals hear as well as we do and some hear very much better. Bats and rats and porpoises can detect sounds higher than 100,000 cycles per second. Our ears are deaf to this super high range. We call it supersonic or ultrasonic sound and use sensitive instruments to detect it.
Our younger friends are very interested in how animals sense things, so let's ex¬plain the meaning of cycles per second. The sounds we hear are vibrations that jog so many times a second. High notes jot; faster and low notes jog more slowly. We may call these vibrations either frequencies or cycles per second. The frequency of middle C is 256 cycles per second.
Most human ears can hear from 20 cycles to 20,000 cycles per second. This is a range of about ten octaves. A million animals have a million different ways to hear. And each species seems to favor a sound range of its own. This makes it possible for them to have private conversations limited to their friends and relatives. A little mouse, for example, can squeak sounds of 100,000 cycles per second. And no doubt his kinfolk can hear him. A cat has keener ears than ours. But she cannot hear the very high squeal: of a little mouse.
Most likely the keenest ears belong to the bat. He uses them to catch echoes from his own high pitched voice. The sounds bounce off walls, branches and other objects as he flies around and the bouncing echoes reach his ears in time to warn him away from collisions. This neat system of sounds and hearing is called echo locating.
Bats utter squeaks of 10,000 cycles per second, which we can hear. They also utter higher sounds in the ultrasonic range, which T ye cannot hear. Many of them utter and hear sounds above 100,000 and some go as high as 150,000 cycles per second. The average bat can hear two or three octaves higher than we can.
Porpoises also use echo locating systems and they, too, are aware of super high fre¬quencies. This can be measured by sensitive equipment lowered into the water. We know for a fact that these clever creatures utter and hear sounds as high as 120,000 cycles per second. Rats and many other animals make and hear sounds in the ultrasonic range, somewhat hi her than humans can hear. And quite a number of them can hear tray above 80,000Frogs and fishes, birds and insects listen with different ears. Naturally the sounds they make match the sounds they are capable of hearing. But many of their conversations are way, way above our limited human ability to hear. For example, when a mouse opens his little mouth in what seems to be silence, he may be uttering a supersonic scream.