Wow, the high-frequency sound thing sounds interesting! I have a time-lapse monitoring system set up on a little experiment "chamber" I have inside (not very permaculture, I know - but in my defence, the lights are low-power LED and the experiments permaculture-based!) -- I use it to see how certain factors (e.g. different green manures/organic teas, substrates, etc) affect growth on tomato plants. I'll try playing high-frequency sound and see if it makes a difference! Does anyone know anything more on the subject? For example, artificial lights (like my LEDs) provide specific wavelengths of light (color), depending on whether the plants are in vegetative growth or flowering. Are there certain frequencies of sound that purportedly affect plants most positively?
Also, I had a quick google, and came across this (from 1988, can you believe it? Has this taken off since then, or been proven to not be true? I wonder!) --
http://www.nytimes.com/1988/09/04/us/scientists-listen-to-noises-of-plants-in-drought.html
Interesting stuff!
