The sound of a sand timer scaled up 90 times. 

Amplified to this scale the dune inside the hour glass would begin to “sing”. A phenomena where sand dunes with certain characteristics create a low frequency hum when there is sand slide or drift. The most notable being, when a dune is naturally composed of fine, uniformed grains, a rare occurrence. A likely outcome of the manufactured sand used for the hourglass. A sonic fantasy.

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Example of the singing dune:

https://www.youtube.com/watch?v=uX-_9IEiFSg