You searched for: “geoacoustics
geoacoustics (s) (noun) (a plural form that functions as a singular)
The use of echo-ranging devices with low-frequency seismographic waves transmitted several miles into the earth's crust to determine the composition and characteristics of the area: "Sam's cousin, Hanson, is a scientist who has developed unique techniques for the use of geoacoustics in his research about the minerals that exist below the surface of the ground."