A group of researchers has recently demonstrated that plants emit an ultrasonic sound when stressed. Although human ears can’t pick up the noise, the scientists have proven that essentially when stressed, plants scream.

In fact, we’ve not known just how complex plants are until relatively recently. For example, not long ago we discovered that plants use the ground to communicate with each other, and we also discovered recently that they respond to “attacks” by emitting signals that experts found to closely resemble animal responses to pain.

Now, a new study has proven that plants, when under stress, produce an ultrasonic screaming noise.

As revealed by researcher Itzhak Khait and his colleagues at the University of Tel Aviv in Israel, plants can produce sounds when they are stressed by either lack of water or when the stem is cut.

Although the results of their study have still not been published in a peer-reviewed journal, the new discoveries are available on BioRxiv.

To make the discovery, the scientists placed microphones near stressed tomato and tobacco plants and started recording. The researchers then found the instruments picked up the plants’ ultrasonic squeals from about 4 inches (10 centimeters) away.

As explained in the paper published in BioRxiv, the plants produced squeals ranging from 20 to 100 kilohertz, a volume that can be detected by organisms located several meters away, the authors explained in their paper.

Both animals, as well as plants, might monitor and react to the silent screams of plants, and possibly humans could too, with the right tools, of course, the authors added.

The notion that “sounds that drought-stressed plants make could be used in precision agriculture seems feasible if it is not too costly to set up the recording in a field situation,” Anne Visscher, a researchers from the Department of Comparative Plant and Fungal Biology at the Royal Botanic Gardens in the U.K who participated in the study, told New Scientist .

Researchers discovered that similar to animals, a variety of plants is able to respond to stress in more ways than one. Some plants are able to release an odorous chemical compound in the air, as well as change their appearance in response to stress.

Animals near plants are able to pick up those signals, and experts have found that even other plants located nearby are able to identify the signals of their neighbors.

Previous studies have discovered that plants reacted to sound, but it remained an enigma whether or not plants themselves were able to produce detectable noises. Earlier studies also investigated whether plants produced noises.

Experts affixed microphones onto the plants and listened for sounds produced inside the stems. They found that plants stressed by either drought or animal bites produced air bubbles that would pop and trigger vibrations within the tissue that usually transports water up the stems. This process is known as cavitation and was picked up by the microphones.

However, the new study by scientists from Tel Aviv University discovered that plants not only produced noise, but it travels through the air and can be picked up by other animals and plants.