And plants are programmed by the forces of evolution, which has no thoughts or feelings. Evolution is merely a succession of mistakes, random mutations. And if a plant's genes happen to mutate in such a way that benefits the plant or its offspring, then the plant spreads this mutation around and it sticks. Why might plants have evolved the ability to effectively screen in pain? Well, let's talk about what these Israeli scientists actually observed, which of course is not literally a scream of pain. That's just the most convenient way we have to describe it because we developed our language chiefly for the purposes of expressing things about ourselves and we're people. Describing plants with a language designed to describe people is like using machine code to say how you feel. It's possible but awkward. This is why even brilliant biologists who need no lecture on the non-teliological nature of evolution will say things like, you know, this plant is much happier in X conditions or this plant really wants to do X or it hates Y. Plants don't have feelings and we don't need an internet pedant to send us a DM to that effect. Anthropomorphism is just a much more convenient way to talk about plants in a human-oriented language like English. These particular humans in Tel Aviv put tomato and tobacco plants inside acoustically isolated boxes. Then they put two microphones on each plant recording at 500 kilohertz. That's 500,000 samples per second. In contrast, the sound of my voice right now is being recorded at 44,100 samples per second which is a pretty standard sample rate for digital audio because it's a little more than twice the rate of the highest frequency sound that any human can possibly hear. The highest sound that any person can hear is about 20,000 hertz. Hertz is a measurement of cycles per second. A cycle of a sound is the positive phase of the wave followed by the negative phase. So vibrating objects alternately push and pull air against your eardrum as they vibrate back and forth. That's the peak and the trough of the wave. A complete cycle from equilibrium air pressure to maximum pressure down to the maximum negative pressure aka pull or vacuum then back up to equilibrium again. That is the cycle measured in hertz. Though confusingly, people also use the word hertz to describe the recurrence of any event per second. Like anything per second is often expressed in hertz even if it's not a two part cycle like a sound wave is.