Klausner reaches the doctor, who answers the phone in a sleepy voice. Klausner asks the doctor to come at once. The doctor asks if Klausner is ill. Klausner says he isn’t, but he wants someone to hear the sound. Klausner says it’s driving him mad; he can’t believe it. The doctor hears the frantic, almost hysterical note in Klausner’s voice and recognizes that it is the same note he hears in people who call to ask him to come to help with an accident.
The doctor says he’ll get out of bed and come right away. Klausner sits beside the phone and waits, thinking about what the tree’s shriek had sounded like. He can’t recall the noise, only that it was enormous and frightful and filled him with horror. He wonders about other living things. He pictures a field of wheat, standing straight and yellow, cut down by a mower driving straight through it. He thinks he would not like to bring his sound machine to a wheat field to hear the hundreds of simultaneous screams. He would never eat bread after that. He imagines a potato, carrot, and onion would also make terrible noises.
He hears the click of the front gate latch and jumps up. Out front, the doctor asks Klausner what the trouble is. Klausner brings him to the park. The doctor observes that Klausner is calmer now; he shows no signs of madness or hysteria. Klausner asks the doctor to put on the headphones. He smiles and puts them over his ears.
Klausner flicks on the machine and picks up the axe. He confirms the doctor hears the humming sound while readying his swing. As he swings, Klausner swears he can feel movement under the ground on which he stands, as if the roots are moving beneath the soil. But it is too late to stop the blow and the axe gouges a deep wedge. Above head is the cracking sound of wood splintering.
The doctor cries for Klausner to look out and runs away fast. Klausner stands spellbound as he watches a sixty-foot branch bending slowly, breaking and crackling at the thick point where it joins the trunk. Klausner leaps aside just in time, but the branch smashes the machine into pieces. The doctor runs back shouting good heavens. Klausner stares at the tree with a tense, horrified expression. He gently pries the axe loose from the tree.
Klausner asks the doctor what he heard. The doctor says he ran as soon as the axe struck and doesn’t know what he heard; probably just the branch breaking. Klausner leans in and stares hard at the doctor. Klausner asks what exactly it sounded like. In an exasperated voice, the doctor says how could he tell when he needed to run for his life. Klausner senses that the doctor is nervous. For half a minute Klausner stares at the doctor in silence. When the doctor suggests they leave, Klausner’s white face becomes suffused with color. Klausner orders the doctor to stitch up the gash he made to the tree trunk—and quickly.
The Doctor tells Klausner not to be silly. Klausner orders him to do as he says and stitch up the tree. Klausner speaks softly in a curious, almost threatening tone while gripping the axe handle. When the doctor says he can’t stitch through wood, Klausner asks if he has any iodine in his doctor’s bag. He says the doctor can paint the cut with iodine; it will sting, but that can’t be helped.
The doctor protests but Klausner insists. The doctor sees Klausner’s hand tightening on the axe. Thinking his only alternative is to run away, and being unwilling to do so, the doctor takes out of his bag iodine and cotton wool. He dabs the cut, keeping one eye on Klausner. Klausner tells the doctor to make sure he gets the iodine right in the cut. The doctor obeys when Klausner demands that he dab the other cut.
The doctor surveys his work in a serious manner and says that it will do nicely. Klausner examines the two wounds and agrees that it will do nicely. He asks if the doctor will come back tomorrow and put some more iodine on the cuts. The doctor says he will. Klausner drops the axe and thanks the doctor, smiling in a wild, excited way. The doctor takes Klausner gently by the arm and says they must go now. Suddenly they are walking in a silent, hurried way across the park, over the road, and back to the house.
In the third and final major scene of “The Sound Machine,” Klausner rushes inside to call the Doctor and urge him to head straight over so he can confirm Klausner’s scientific findings. The doctor is reluctant to get out of bed and attend to Klausner when he isn’t ill, but, hearing the frantic, hysterical note in Klausner’s voice, he obliges, implying that the doctor is worried about Klausner’s spiraling mental health.
As he waits for the doctor to arrive, Klausner considers the consequences of his findings. Furthering the theme of the personification of plants, Dahl depicts Klausner remembering the horror he felt when he hit the tree with the axe and imagining the scream a field of wheat must make when mown down. Klausner is terrified to think of what sounds common vegetables might make—non-animal living beings people eat while believing they are causing no harm.
The doctor assesses Klausner when he arrives and is relieved to see no signs of madness or hysteria in Klausner’s calm demeanor. They go to the park to recreate the test with the tree. However, in an instance of situational irony, the test is brought to an abrupt and unexpected end when the force of the axe swing causes one of the tree’s largest branches to crack away from the trunk and smash the sound machine as the branch crashes to the ground.
While the doctor runs clear of the falling branch, Klausner only jumps aside at the last moment. The doctor is rattled by the experience but grateful neither of them were injured. Klausner, however, looks upon the tree in horror and removes his axe blade from the deep gouge he made in the trunk. Klausner’s first question is whether the doctor heard anything, but the doctor disappoints him by being unable to confirm the low, growling sound.
With his sound machine destroyed, Klausner has lost his outlet with his obsession and also the device that would have turned his subjective experience of reality into scientifically objective, observable reality. No longer tethered to objective reality, Klausner abandons the need to confirm his subjective experience and pours his obsession into the tree itself by demanding that the doctor stitch the tree’s wounds. The doctor pushes back against the absurd suggestion and also the suggestion that he apply iodine. However, the doctor sees Klausner’s hands tighten on the axe handle; the doctor believes his only options are to run away from the madman or do as he says.
After the doctor applies the iodine, playing along with Klausner’s illogical conception of reality, the threatening atmosphere dissipates. Klausner reveals his sensitivity as he drops the axe and assures the tree that it will heal. With the threat neutralized and Klausner’s defenses down, the doctor insists that it is time to go. The story closes on the image of the doctor hurrying Klausner back to his house, suggesting that Klausner’s break with reality has confirmed his suspicion throughout the story that Klausner’s mental health is unstable.
With this ambiguous ending, Dahl leaves open the question of whether Klausner truly heard the flowers and tree making sounds of pain. Regardless, Klausner has lost the machine that could prove his findings to other people; as far as society is concerned, he is a madman and not a genius inventor.