Archaeoacoustic Investigation of a Prehistoric Cave Site: Frequency-Dependent Sound Amplification and Potential Relevance for Neurotheology

Abstract

An archaeoacoustic study was recently conducted within the important prehistoric cave system of El Castillo in northern Spain. With findings dating back at least 40800 years, archaeological studies of this cave have revealed the presence of prehistoric ritual activity associated with early shamanism. Simulated audio tones of varying frequencies were created and emitted from the location at which it is thought the shamans would conduct rituals within El Castillo, while the sound was simultaneously recorded from the likely location of potential observers or participants. Subsequent analysis identified a frequency-dependent amplification of recorded sound intensity for frequencies approaching the range of 100 Hz, with the greatest effect observed for 108 and 110 Hz. These results are markedly consistent with previous research of important or sacred sites which have shown significant sonic resonance features within this precise range of frequencies. Additional consideration is applied to the potential effects of 110 Hz physical stimuli on biological systems in the context of neurotheology and the associated biophysical analyses in order to demonstrate the potential importance of 110 Hz signals on religious experience and subjective states of consciousness.