The results of recent research suggests that ancient, or prehistoric, builders of the monumental structures found in such diverse places as Ireland, Malta, southern Turkey and Peru all have a peculiarly common characteristic — they may have been specially designed to conduct and manipulate sound to produce certain sensory effects.
Beginning in 2008, a recent and ongoing study of the massive 6,000-year-old stone structure complex known as the Hal Saflieni Hypogeum on the island of Malta, for example, is producing some revelatory results. Like its related prehistoric temple structures on Malta, this structure features central corridors and curved chambers. But this structure is unique in that it is subterranean, created through the removal of an estimated 2,000 tons of stone carved out with stone hammers and antler picks. Low voices within its walls create eerie, reverberating echoes, and a sound made or words spoken in certain places can be clearly heard throughout all of its three levels. Now, scientists are suggesting that certain sound vibration frequencies created when sound is emitted within its walls are actually altering human brain functions of those within earshot.
“Regional brain activity in a number of healthy volunteers was monitored by EEG through exposure to different sound vibration frequencies,” reports Malta temple expert Linda Eneix of the Old Temples Study Foundation, “The findings indicated that at 110 Hz the patterns of activity over the prefrontal cortex abruptly shifted, resulting in a relative deactivation of the language center and a temporary shifting from left to right-sided dominance related to emotional processing and creativity. This shifting did not occur at 90 Hz or 130 Hz……In addition to stimulating their more creative sides, it appears that an atmosphere of resonant sound in the frequency of 110 or 111 Hz would have been “switching on” an area of the brain that bio-behavioral scientists believe relates to mood, empathy and social behavior. Deliberately or not, the people who spent time in such an environment underconditions that may have included a low male voice — in ritual chanting or even simple communication — were exposing themselves to vibrations that may have actually impacted their thinking.” 
Researchers at the University of Malta are confirming the findings in an ongoing study.