Link zu WSL Hauptseite Swiss Federal Institute for Forest, Snow and Landscape Research WSL
Duration: 2012 - 2015

trees: Rendering Ecophysiological Processes Audible

Measuring station in Salgesch/VS

Fig. 1: Setup of acoustic emission sensors on a Scots pine (Pinus sylvestris) at Salgesch/VS

trees: Rendering Ecophysiological Processes Audible is a research project conducted by the Institute for Computer Music and Sound Technology (ICST) of the Zurich University of the Arts ZHdK and the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL)

Plant physiologists have known that plants emit sounds for several decades now. Most of these sounds are of transpiratory/hydraulic origin and are therefore related to the circulation of water within the plant as part of the transpiration process. The frequency of the acoustic emissions is in the ultrasonic range, i.e. well above the audible range. By analyzing these acoustic emissions, we can find out more about plant physiology and the ecophysiological processes in plants: If the sap flow is interrupted inside a plant’s vessels (a phenomenon known as “cavitation”), for example in a severe drought, the plant emits ultrasonic pulses that are imperceptible to the human ear – in other words, the plant begins to “whisper” in the high-frequency range. This phenomenon per se has been known for several decades and shows how atmospheric conditions, diurnal rhythm patterns, light conditions and water reserves manifest themselves acoustically, as it were, in trees.

Acoustic emissions of a Scots pine (Pinus sylvestris)

Fig. 2: Acoustic Emissions of a Scots pine (Pinus sylvestris).

In our research project trees, we are working on the acoustic recording, analysis and representation of ecophysiological and climatic processes and studying the acoustic and aesthetic requirements for making them perceptible. Measurements of acoustic emissions in plants must be analysed and understood in relation to other measurement data such as that relating to the microclimate, sap flow, changes in trunk radius and water potential in the plants’ organs – all measurement data that is not auditory per se. Therefore, in our research project trees, we deal with the sonification of ecophysiological data as well as analysing the actual acoustic emissions: How can processes that are beyond our normal perception be made directly perceptible, creating new experiences and opening a new sight on processes in nature? To what extent is our sense of hearing of use?

  • Contact
  • Links to related projects

Rhythm of Trees



  • Publications

Maeder M, Zweifel R (2013) Downy Oak: Rendering Ecophysiological Processes In Plants Audible, Proceedings SMC/SMAC 2013, Stockholm, Sweden

  • News and Reports about the project (in German)

· 2. Jul. 2015: 1h radio program about the project 'trees'Ö1 (Austrian radio)

· 23. Apr. 2015: US-ambassador LeVine visits  'trees', Salgesch 

· 16. Apr. 2015: State president of France, Francois Hollande, visits 'trees', ZHdK

· 5. Mrz. 2014: Für junge Neugierige: Wie Pflanzen flüstern, WSL

· 4. Jun. 2014: Die leise Symphonie der Bäume, SRF Kultur

· 6. Jun. 2014: Das Flüstern der Föhren, Die Zeit (D)

· 23. Jun. 2014: Die leise Symphonie der Bäume,

· 16. Okt. 2014: Wachsende Bäume machen Musik, Tierwelt

· 17. Oktober 2014: Der den Baum belauscht, Radioreportage 'dradio wissen' (D)

· 8. Nov. 2014: Ein Baum singt in den höchsten Tönen, Beobachter Natur

· 9. Nov. 2014: Die Bäume wachsen hören, Zentralschweiz am Sonntag

· 18 Nov. 2014: Gesang der Bäume, TV-Report on 3Sat, NANO

· coming soon: Das Flüstern der Kiefer, Zuschnitt (A)


'trees' is funded by the Swiss National Science Foundation (SNSF), the Zurich University of the Arts ZHdK, and the WSL

Keywords Ecophysiology, Data Sonification, Forest Dynamics, Artistic Research, Plant Bioacoustics