Listen to the Voices of Plants: Evaluate leaf water content with acoustic response of leaf

Sakura Niki – s21a4113hj@s.chibakoudai.jp

Chiba Institute of Technology, Narashino, Chiba, 275-0016, Japan

Popular version of 1pEA11 – Investigation of the relationship between a circular diaphragm model and measured leaf natural frequency to evaluate leaf water content.
Presented at the 189th ASA Meeting
Read the abstract at https://eppro02.ativ.me//web/index.php?page=Session&project=ASAASJ25&id=3983223

–The research described in this Acoustics Lay Language Paper may not have yet been peer reviewed–

Have you ever wanted to listen to the voices of plants when they need water? If you use our method, you can.

We focused on changes in the acoustic frequency characteristics of the leaf after we stopped watering. Currently, we are developing a method to evaluate leaf water content through its acoustic response for plant-human communication.

Figure1. Proposed method for evaluating leaf water content through its acoustic response

In this study, we confirmed that leaf natural frequency showed complex behavior with losing water content. Despite this complexity, we demonstrated the estimation of its frequency change using an equation based on the circular diaphragm theory.

Our research steps were conducted in the following order: I. Measurement of leaf natural frequency, II. Estimation of leaf natural frequency, and III. Comparison of measured and estimated values.

First, in “I. Measurement of leaf natural frequency,” we obtained the acoustic frequency characteristics of the leaf under non-irrigation conditions by vibrating the leaf using a bone-conduction transducer. The results showed that the natural frequency showed non-monotonic and complex changes over time as leaf water content decreased. Based on the leaf Young’s modulus and thickness measured simultaneously as physical parameters, we confirmed that the complex changes in natural frequency were due to independent changes in these physical parameters.

Next, in “II. Estimation of leaf natural frequency,” we derived an estimation equation by applying a first-order approximation to the circular diaphragm theory to clarify the leaf vibration behavior under non-irrigation conditions. The estimated values were calculated by substituting the measured physical parameters into the estimation equation.

Figure 2. Estimation equation to estimate leaf natural frequency

Finally, in “III. Comparison of measured and estimated values,” we compared the measured natural frequency in step I with the estimated natural frequency in step II using correlation coefficients. The results showed that the estimated values showed high correlation coefficients with the measured values (0.66–0.83). We concluded that the estimated equation based on the circular diaphragm theory can be applied to leaf vibration.

Figure 3. Comparison of measured and estimated leaf natural frequency changes under stopped watering

Through this study, we investigated the relationship between the leaf vibration characteristics and water content, and we clarified this relationship as a preliminary step. Based on these findings, we aim to establish a quantitative measurement method for evaluating leaf water content using its acoustic response.

Once this proposed method is established, we will be able to hear the voices of leaves when they are thirsty.