Stimulated by the studies done by Paul Deveraux and Robert Jahn, research has been conducted on the sound properties of two megalithic chambers is Ireland: Dowth South and Fourknocks I. As reference measurements two normal rooms (bed- and bathroom) have been studied. The following aspects will be covered in the presentation: some theoretical background on acoustical modes (within a passage, a chamber, and a combination of them: Helmholtz resonator); tips for doing sound experiments inside megalithic chambers (like: equipment, measurement software, power provisioning and calibrating); frequency response measurements (between 20 and 200 Hz) for the surveyed chambers/rooms; comparison of the results with other researchers' results; background on the pitch of the human (male, female, and child) voices in neolithic times and recommendations for future research. The presentation also provides insight in the aeralization (simulation) of sound in a megalithic chamber, covering: software that can do these simulations; issues in finding the basic information, e.g., acoustic absorption coefficients and provide examples of the results. I would like to thank all the people who have provided constructive feedback on my work (http://www.iol.ie/approxgeniet/eng/megasound.htm).