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 under conditions 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." 
But the Hypogeum is not alone in its peculiar sound effects. A study conducted in 1994 by a consortium from Princeton University found that acoustic behavior in ancient chambers at megalithic sites such as Newgrange in Ireland and Wayland's Smithy in England was characterized by a strong sustained resonance, or "standing wave" in a frequency range between 90 Hz and 120 Hz. "When this happens," says Eneix, "what we hear becomes distorted, eerie.
As I said in a previous post, I'm always a bit suspicious when people try to say exactly what and why people were doing things 6,000 years ago, but the evidence does seem to indicate the ancients were not unaware of how sound can be an effective part of rituals.