The story "The Sound Machine" by Roald Dahl is the tale of an inventor, Klausner, who extends the range of human hearing by creating a machine that can translate sounds made by plants into sounds humans can hear. He realizes his invention has succeeded when, while wearing the sound machine's apparatus, he hears the inhuman scream of a flower being cut in his neighbor's garden. To confirm his hypothesis, he asks Mrs. Saunders to cut another flower, and he hears another scream as its stem is severed.
A critical analysis of the story would include a discussion of its themes, particularly obsession. Klausner becomes fixated with his invention, even to the expense of healthy relationships with Mrs. Saunders and a professional colleague (Dr. Scott). In completing your analysis, you could look for examples of how Klausner demonstrates obsession with his invention. What sorts of tests does he run to experience new sounds with the sound machine? What does it say about Klausner's character that his experiments cause what he interprets as pain—yet he continues carrying them out?
When Klausner consults Dr. Scott near the end of the story, Dr. Scott is unable to hear the sounds Klausner does. Dahl thus introduces the possibility that Klausner's obsession has led him to imagine the success of his experiment. When the sound machine is destroyed, Klausner feels disappointment, of course, but also perhaps that justice has been done. His fate is ambiguous, as is the success of his invention.