it was difficult to get a good A4
just by listening to A4 and the fork directly. One reason for this could be that when you are really close,
it is impossible to know whether A4 is sharp or flat. Another important fact that many people don't realize,
is that when A4 and the fork sound good together,
A4 may not actually be at 440Hz. Another way to say this is, when A4 = 440 Hz exactly,
A4 and the fork together may not sound as good as they could.
The reason for this is that A4 and the fork are not matched.
Scientifically speaking, they do not have the same inharmonicity,
which means that the higher partials of A4 and the fork
do not line up with each other.
Click the [A4-Fork] button below.
A4 is the exact same frequency as the fork.
But the third partials of A4 and the fork do not line up.
Click the A4-Fork Filtered at E6 (3rd partial) button below
and listen to the wild beating at that frequency. You should be able to hear the fast beating E6
when clicking the A4-Fork button. It's in there!
Click the button below for A4 = 439.24 Hz and the fork.
This interval may sound better to you because
there is less beating at both partials,
but A4 does not equal 440 Hz.
In fact it is 3 cents flat
and fails the Registered Piano Technicians exam! Listen to the filtered beats at A4 and E6.
They are both slow and that's what may make this unison
sound better to some people than the [A4-Fork] button
where A4 = 440 Hz.