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.
Example of the singing dune: