Acoustical Detection of Aircrafts
From the first world war until the 30's air acoustics played an important role in the air defence. As radar was still to be discovered, vision had to be supplemented by hearing using the sound of the engines. (MUSEUM "WAALSDORP": TNO-FEL Museum).

Rock Art Acoustics
Steven. J. Waller's Home Page

Chirped Echo from the Mayan Pyramid of Kukulkan at Chichen Itza
David Lubman of the Acoustical Society of America argues that the echo sounds like the primary call of the Mayan sacred bird, the Quetzal.

Stone Structures and Sound

Moving Beyond Prophecies & Predictions
By Cynthia Gage (Atlantisrising)