thanks to gb for pointing me to p22 of Elements and to R for a well
detailed and elegant response.

certainly convinced to abandon all hope at this time. in the meantime i
suppose i will gain whatever perceptive sense there is to gain for
manipulating timbre just working with plain old decibels. as my primary
objective is to improve judgement for tweaking relative strengths of
partials within a musical tone constructed via additive synthesis, rather
than the overall perceived volume of the resulting musical tone, let alone
its presence in the overall mix, i may just as easily struggle, as i go, to
develop a sense for adjusting volume of sine waves using different numbers
of decibels at different frequencies. moreover any such decibel perception
may prove useful in other situations and would certainly not be gained
through reliance on a mathematical model programmed by others.

still think sones would be a great marketing coup though. can't you just
see that multicolored 3D fletcher-munson leaping through your eyeballs the
minute you turn to that page in the magazine?

yours,
tolve