“The Sound Machine” opens on a warm summer evening. A man named Klausner goes to his garden shed and tinkers with a black box full of wires. The box is three feet long and shaped like a child's coffin. He works with intense concentration and suppressed excitement while muttering to himself.
A doctor stops by to see how Klausner is doing and to ask if his throat is feeling better. Klausner says he is fine. The doctor feels tension in the room and asks what Klausner is working on. Klausner is evasive at first but when pressed admits he has invented a device that can transmit sounds so high-pitched the human cannot normally detect them. Klausner says he imagines there is an infinite amount of sounds humans cannot hear, getting ever higher. Klausner grows animated as he speaks. The doctor feels there is an immeasurable distance between Klausner's mind and body.
Klausner says his device can turn high-pitched sound vibrations into tones heard through headphones, translated into much lower pitches. He says he is trying the box out tonight. The doctor wishes him luck and leaves. Klausner goes out to the garden and begins his test by plugging in his headphones. Mrs. Saunders, his next-door neighbor, is clipping roses in the yard. He switches on the machine and hears a faint crackling. Soon he hears a shrieking sound. He realizes the shrieking occurs every time his neighbor snips a rose stem.
Klausner is thrilled. He asks Mrs. Saunders to cut another. She thinks he is peculiar, but she humors him; he hears the same shriek. Mrs. Saunders dashes inside while Klausner picks a daisy and listens for its faint cry of pain.
Klausner rises first thing in the morning and takes his sound machine across the street to the park. His next test involves listening as he swings an axe at the base of a tree. Unlike the roses’ brief shriek, the tree’s noise is like a sob, lasting for a minute and gradually fading. Klausner feels horrified and tries to push the sides of the axe wound back together. He insists to the tree that it will heal.
Klausner goes back to his house and phones the doctor, waking him up. Klausner won't explain why, but he insists the doctor come straight over. The doctor obliges and Klausner makes him wear the headphones while Klausner strikes the tree again. This time one of the tree's largest branches cracks away from the trunk, smashing the sound machine as it falls.
The doctor is relieved neither of them got hurt. Klausner only wants to know what the doctor heard. The doctor stumbles with his words and says he isn't sure what he heard because he was focused on running out of the way. Klausner speaks in a threatening voice and grips his axe; he tells the doctor to stitch the gashes in the tree. The doctor tells him he can't stitch wood. Klausner asks if he has iodine in his medical bag and tells the doctor to paint the cut.
The doctor resists at first but obliges when he sees Klausner's hand tightening on the axe. The doctor plays along, seriously applying the iodine and saying it will do nicely. Klausner agrees and asks if the doctor will return tomorrow to examine the healing and apply more. He says he will. Klausner drops the axe and thanks him in a wild, excited way. The Doctor walks Klausner back to the house, hurrying across the park and road.