This morning I was listening a beautiful sound of an aeolian harp from the Youtube. It’s so naturally relaxing and it’s perfect for me to get my mind fresh for the day. This sound was amazingly tuned by the size (diameter) of the string (infinite circular cylinder) and the level of wind speed. In aeroacoustic engineering, they named this airborne noise mechanism as an aeolian tone. It’s actually a dipole type of sound radiation.

Aeolian harp sound radiation is different from the sound radiation from a loudspeaker (monopole) or noise from the engine jet (quadrupole).  The sound sources of aeolian harp consist of two monopole sources of equal strength, but they are in opposite phase. The two sources are located very close to each other when compared to its sound wavelength.

We can control this sound beautifully. Using Lighthill’s acoustic analogy and Curle’s equation for the inclusion the effect of aeolian tone,  we can see how the aeolian tones is controlled by just using a thin flat plate. Please visit my publications if you like to see more.