Helmholtz Resonance occurs when this oscillation becomes synchronized with the pressure waves emitted by the sound source, causing these waves to increase in amplitude.
Helmholtz Resonance could, therefore, contribute to the experience of being inside the tomb.
In the modern world there are no acoustic instruments which can generate a note sufficiently low to induce Helmholtz Resonance at Camster Round.
Cavities within the dry-stone walling may reduce the amplitude of Helmholtz Resonance to some extent, but would not affect the frequency.
When reduced by a factor of 10, these results equate with frequencies between 4 and 6 Hz at Camster Round, and correspond closely with the theoretical prediction for Helmholtz Resonance.
These results imply that it would be possible to produce Helmholtz Resonance in the chamber, but would this phenomenon have been noticeable?
While it is possible that the noise and rhythm of drumming in the enclosed environment could itself influence behaviour, there were fewer complaints during equally loud sequences at beats which were too slow to excite Helmholtz Resonance.
Helmholtz Resonance would not be restricted to Camster Round, and the resonant frequencies of a sample of other passage-graves were calculated by deducing their internal volumes from plans and elevations.
In general the larger tombs have lower resonant frequencies, and would require a slower drum-beat to evoke Helmholtz Resonance.