para-inharmonicity and tuning curves

[Richard Moody]

And if a partial is really
> really weak, who cares what its frequency is?  No one will hear
> it.
> 
> -Robert Scott
>  Ann Arbor, Michigan

That is a very good question.In piano tuning we are concerned with the
beats caused by coincident partials. We really notice partials when they
beat. The question is, how weak does a partial have to be not to cause
beats? In terms of audible strength (decibles?) the fundamental is louder
than the second partial.  The second partial is louder than the third and
so on, or so it should seem. Yet the beatings do not sound any louder or
softer according to how loud or weak the partial is. 
 Why does it seem a 5/4 third beats as loud as a 2/1 octave. One would
think  the first and second partials would be at least twice as loud as
the fourth and fifth partials. Shouldn't that affect the loudness of the
beats? 
Ric