I got my first crystal singing bowls yesterday. In addition to playing with them, and programming them with healing intentions for the highest good, I had to more thoroughly (and qualitatively) explore an interesting phenomenon I was hearing. They are tuned to ca. D (11″) and F# (8″). When played together, I heard a distinct and quite loud low E subtone. This is odd, since F# is part of the harmonic spectrum of the D bowl, and so I would think that any subtone I would be hearing would be a D of some sort. So, I recorded them, and did a spectral analysis of their sound together. And guess what? They are not producing that low E tone. A frequency of 82 Hz (E) simply is not present in the spectrum of the recorded sound. What does this mean? Well, since the sound is not present in the physical vibration of the bowls, it means that it is a psychoacoustic phenomenon (i.e. supplied by the mind as a difference tone).
I want to explore this more, but what is interesting to me is that after reading Rudolf Steiner mention that the interval of Atlantis (something that i’ve been spending a lot of time on lately and trying to compose), was the 7th. Not sure where he got this (something I also want to explore), but it is worth noting that the interval between the 82 Hz E phantom subtone, and the fundamental of the 11″ bowl in D, is a 7th (plus one octave).
Incidentally, this phenomenon of psychoacoustic tones is not new. The D string on the violin, for example, is like this too. It simply does not vibrate at the note we are hearing (i.e. that frequency is not present physically in the spectrum of the sound) because of the oddities of the string length and density, etc. It is our mind that is summing the harmonic spectrum (“adding together” the upper partials), and providing the D. Some things, after all is said and done…are only in our heads.