Refraction of Sound Waves

October 19, 2020

Dungeness Field Joe LaCour

Photographer: Joe LaCour
Summary Author: Joe LaCour

The field next to our property in Dungeness, Washington provides an example of the refraction of sound waves. When the wind is calm, and the sun has heated the air close to the ground higher than the air above the ground, the sound travels faster close to the surface and slower above the surface. With this temperature gradient sound is curved upward, and the vehicles traveling on the road can hardly be heard.  But when there’s no temperature gradient because of a thick overcast or it’s windy, the road noise is very loud. The inverse example is the noise from jet aircraft on Whidbey Island being heard on the Olympic Peninsula. When the cold water in the Strait of Juan de Fuca has cooled the air close to the surface to a lower temperature than the air above the surface, sound is curved downward and the concentrated sound travels along the surface. Thus the sound can be very loud quite a distance away.

Photo Details: Camera: Leica M9; Lens: Summicron 35mm; Exposure Time: 0.0028s (1/360); Aperture: ƒ/8.0; ISO equivalent: 60; Focal Length (35mm): 5.