During our thanksgiving break, my father Al and I were talking about the various sound-listening ideas related to our sound planetarium idea, and he suggested turning the problem around. Rather than hearing a sound from a particular direction, how about directing ourselves using sound. In other words, could we define a two-dimensional spherical coordinate system where we could, with a single utterance, orient ourselves? After some trial and error, we came up with the following mapping:
In a nutshell: four vowel sounds are used to indicate azimuthal direction, with blends to assign intermediate angles (e.g., pure “ay” would be 0º, an “ay-ee” blend would be around 45º), while pitch indicates altitude. We played around with various vocal ranges that would fit both men and women, coming up with a nominal range of E4 (330 Hz) to E5 (659 Hz), somewhere in the countertenor range, although in principle the equatorial altitude could be set to any pitch and the poles set to a half octave above and below. The vowel tones could also be modified to those of a person’s native language.
I imagine this tonal directional language being used to control a telescope in a hands-free method, but I expect the degree of precision to be pretty poor – with practice I estimate no better than 10º precision – but that would be sufficient to match the angular precision of our hearing, so perhaps well suited to controlling the direction of a sound planetarium!