There is interesting if rather controversial research which showed that even though humans can't usually hear over 20K there were signs of activity being generated in their brains when they were exposed to frequencies over 20K. A number of people were bringing this up to support SACD and DVD Audio. I have seen measurements and a number of common instruments can produce overtones well up into the 40K range.
I never got to read the scientist's results and testing methodology directly though, only second hand reports, some of which claimed the research was fundamentally flawed.
I never got to read the scientist's results and testing methodology directly though, only second hand reports, some of which claimed the research was fundamentally flawed.