Originally posted by: jagec
This and
this seem applicable.
One of those sites suggested headphones, so I gave mine a shot. Labtec Icon-750's. They make a high pitched whine up to about 19HKz. At 20KHz though, the frequency shifts down a bit, and they start to make a weird buzzing noise too, but at a higher pitch than my speakers made.
I guess most companies don't see much market though in making audio equipment that can produce sounds that their customers can't hear.
Goldwave - one nice feature is its audiograph thing.
Under the Tool menu, select Control.
It might be default, but if not, right click the area below the controls and select Spectrogram.
Right click again and select Properties. Make sure it's set to Automatic Full Frequency Range and that Show Axis is enabled.
Now when you play a file, you can see what frequency or frequencies are being produced.