The ultrasound has worked fine for us for over three years now.  Although
it is not in a museum setting.  Perhaps the difficulty is that people
believe the manufacturers hype.  If you do not have instrumentation to
measure the output and directionality of an evaluation unit, then you
will need to be able to take the specified output (normally in decibels)
and apply the atmospheric attenuation at your altitude.
 
My personal background consists of degrees in Physics and Geology coupled
with 40 years in the computer field.  The only reason for my presence on
this listserve is that I was roped into accepting chairmanship of the
board of directors for our small local interpretive museum and am using
this as well as texts to attempt to learn at least something about the
museum profession.  Due to my hard science background plus industrial
experience in research for NASA and some fond memories of Apollo days,
I don't share your faith in "scientific, controlled" research or studies.
 
If the ultrasound unit does not have an adequate warrantee of at least
30 days, I would steer clear of it.
 
Incidentally the original posting was simply a suggestion to be investigated
and should not be read as any sort of testamonial for a particular
manufacturer.
 
                            Lou Lucke
                            Montana State University - Northern
                            Havre, MT 59501
                            (406)265-3765
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