Hi Jammer,
Jammer wrote:As to whisper chamber construction, even the ones we know about were DISCOVERED after construction! They were not designed to do that effect...

For those who have studied the subject it becomes evident the ancient cultures worldwide seemed to have practiced some form of acoustical engineering on a level using a method, we have yet to comprehend. The Oracle Chamber in the Hypogeum at Malta is a 6000-year old example of acoustical engineering from the ancient world preceding Ancient Egypt.

[viewzone2.com]

Science Officer at the Hypogeum, Joseph Farrugia describes unusual sound effects in the UNESCO World Heritage Site:
There is a small niche in what we call 'The Oracle Chamber', and if someone with a deep voice speaks inside, the voice echoes all over the hypogeum. The resonance in the ancient temple is something exceptional. You can hear the voice rumbling all over."
As anyone who sings in the shower knows, sound echoing back and amplifying itself from hard walls can do unusual things. That effect is magnified several times over in the stone chambers. "Standing in the Hypogeum is like being inside a giant bell," says Eneix. "You feel the sound in your bones as much as you hear it with your ears. It's really thrilling!"

Here are other examples of this same form of acoustical phenomenon as found in the ball court of Chichen Itza. They are: Newgrange in County Meath, and Cairns L and I, Carbane West, in Ireland. Then there is Wayland’s Smithy, Chun Quoit, and Cairn Euny, all in the Britain dating to around 3500 B.C.

[www.icrl.org]

And:

[www.theveritasmagazine.com]

A recent study evaluated the possibility that tones at these frequencies might specifically affect regional brain activity. In a pilot project, 30 healthy adults listened to tones at 90, 100, 110, 120, and 130 Hz while brain activity was monitored with electroencephalography (EEG). Activity in the left temporal region was found to be significantly lower at 110 Hz than at other frequencies. Additionally, the pattern of asymmetric activity over the prefrontal cortex shifted from one of higher activity on the left at most frequencies to rightsided dominance at 110 Hz.

These findings are compatible with relative deactivation of language centers and a shift in prefrontal activity that may be related to emotional processing. (see Left Brain:Right Brain by Dan Eden). These intriguing pilot findings suggest that the acoustic properties of ancient structures may influence human brain function, and suggest that chanting might have been used to enhance right brain activities.

Seems to me they could have very well been designed with a particular purpose in mind.

Regards
Jacob