An Israeli research team has found that plants such as tomatoes make high-pitched sounds that humans cannot hear when they are stressed, such as running out of water.

An Israeli research team published this in the American scientific journal Cell on March 3.

The research team used two microphones to record what sounds the plants produced when they were subjected to various stresses, such as exposing them to a dry environment without water or cutting stems, by placing them in a box that blocked out the sound from the surrounding area.

As a result, it was found that these plants produce high-frequency sounds that humans cannot hear after being stressed.

When the research group adjusted the generated sound so that it could be heard by humans, they heard a continuous "pop, pop, pop" sound.

Analysis of sound also revealed that the characteristics of the sound differ depending on the type of plant and the type of stress.

Although the mechanism by which these sounds are generated is unclear, the research group analyzes that they may be caused by small bubbles that form in the stem, and point out that "there are creatures in nature that can hear ultrasonic waves, which may affect the behavior of creatures that hear the sounds."