(Roald Dahl, 1949)
He was shifting from one foot to the other, tugging at the lobe of his ear, looking at his feet, and then at last, slowly, he said, “Well, it’s like this…the theory is very simple really. The human ear…you know that it can’t hear everything. There are sounds that are so low-pitched or so high-pitched that it can’t hear them.”
“Yes,” the Doctor said. “Yes.”
“Well, speaking very roughly, any note so high that it has more than fifteen thousand vibrations a second—we can’t hear it. Dogs have better ears than us. You know you can buy a whistle whose note is so high-pitched that you can’t hear it at all. But a dog can hear it.”
“Yes, I’ve seen one,” the Doctor said.
“Of course you have. And up the scale, higher than the note of that whistle, there is another note—a vibration if you like, but I prefer to think of it as a note. You can’t hear that one either. And above that there is another and another rising right up the scale for ever and ever and ever, an endless succession of notes…an infinity of notes…there is a note—if only our ears could hear it—so high that it vibrates a million times a second…and another a million times as high as that…and on and on, higher and higher, as far as numbers go, which is…infinity…eternity…beyond the stars.” […]
Klausner sighed and clasped his hands tightly together. “I believe,” he said, speaking more slowly now, “that there is a whole world of sound about us all the time that we cannot hear. It is possible that up there in those high-pitched inaudible regions there is a new exciting music being made, with subtle harmonies and fierce grinding discords, a music so powerful that it would drive us mad if only our ears were tuned to hear the sound of it. There may be anything…for all we know there may—”
“Yes,” the Doctor said, “But it’s not very probable.”
“Why not? Why not?” Klausner pointed to a fly sitting on a small roll of copper wire on the workbench. “You see that fly? What sort of noise is that fly making now? None—that one can hear. But for all we know the creature may be whistling like mad on a very high note, or barking or croaking or singing a song. It’s got a mouth, hasn’t it? It’s got a throat!”
The Doctor looked at the fly and he smiled. He was still standing by the door with his hands on the doorknob. “Well,” he said. “So you’re going to check up on that?”
“Some time ago,” Klausner said, “I made a simple instrument that proved to me the existence of many odd inaudible sounds. Often I have sat and watched the needle of my instrument recording the presence of sound vibrations in the air when I myself could hear nothing. And those are the sounds I want to listen to. I want to know where they come from and who or what is making them.” […]
He put his left hand on the volume control and his right hand on the knob that moved a needle across a large central dial, like the wavelength dial of a radio. The dial was marked with many numbers, in a series of bands, starting at 15,000 and going up to 1,000,000.
And now he was bending forward over the machine. His head was cocked to one side in a tense, listening attitude. His right hand was beginning to turn the knob. The needle was travelling slowly across the dial, so slowly he could hardly see it move, and in the earphones he could hear a faint, spasmodic crackling.
Behind this crackling sound he could hear a distant humming tone which was the noise of the machine itself, but that was all. As he listened, he became conscious of a curious sensation, a feeling that his ears were stretching out away from his head, that each ear was connected to his head by a thin stiff wire, like a tentacle, and that the wires were lengthening, that the ears were going up and up towards a secret and forbidden territory, a dangerous ultrasonic region where ears had never been before and had no right to be.