Scientific American – Microphones capture ultrasonic crackles from plants that are water-deprived or injured: “Plants do not suffer in silence. Instead, when thirsty or stressed, plants make “airborne sounds,” according to a study published today in Cell. Plants that need water or have recently had their stems cut produce up to roughly 35 sounds per hour, the authors found. But well-hydrated and uncut plants are much quieter, making only about one sound per hour. The reason you have probably never heard a thirsty plant make noise is that the sounds are ultrasonic — about 20–100 kilohertz. That means they are so high-pitched that very few humans could hear them. Some animals, however, probably can. Bats, mice and moths could potentially live in a world filled with the sounds of plants, and previous work by the same team has found that plants respond to sounds made by animals, too…” [this article includes an audio file]

See also Cell, Khait, Lewin-Epstein, et al. ‘Sounds emitted by plants under stress are airborne and informative’ https://www.cell.com/cell/fulltext/S0092-8674(23)00262-3 DOI: 10.1016/j.cell.2023.03.009 -“What does a stressed plant sound like? A bit like bubble-wrap being popped. Researchers in Israel report in the journal Cell on March 30 that tomato and tobacco plants that are stressed—from dehydration or having their stems severed—emit sounds that are comparable in volume to normal human conversation. The frequency of these noises is too high for our ears to detect, but they can probably be heard by insects, other mammals, and possibly other plants. “Even in a quiet field, there are actually sounds that we don’t hear, and those sounds carry information,” says senior author Lilach Hadany, an evolutionary biologist and theoretician at Tel Aviv University. “There are animals that can hear these sounds, so there is the possibility that a lot of acoustic interaction is occurring.” Although ultrasonic vibrations have been recorded from plants before, this is the first evidence that they are airborne, a fact that makes them more relevant for other organisms in the environment. “Plants interact with insects and other animals all the time, and many of these organisms use sound for communication, so it would be very suboptimal for plants to not use sound at all,” says Hadany…”