Gorman,
did you talk with your audiologist about the results? What did he say?
Was you whole treshold elevated throughout the frequency range or just that 4kHz frequency range?
Be warned that "self-made" audiometry can border on gimmickry. I have the Digital Recording CD hearing Check CD and while useful, it is not a substitute for a test done by a trained audiologist using dedicated equipment.
Reasons:
1) no <15 dB isolate room
2) no audiology headphones (different frequency response than normal headphones)
3) no calibrated gear
4) different test tones (pulse tones are more accurate than the sweeps used by home made tests)
5) no training in conducting, retrying and verifying the test results
Ref: Introduction to Audiology 8th ed., Martin Clark, Allyn & Bacon, 2003.
As such, I wouldn't give too much credit to home made audiometry results.
Also, be noted that there is no accepted and accurate standard to gauge listening treshold beyond 11 kHz.
Why? Because the results can vary with the same test subject from one day to another c. 30 dB. Not very accurate, is it.
Regardless, I've been tested by a local leading audiology research up to and including 14 kHz (flat in both ears up to 11 kHz, slow decline after that, normal for my age).
I can still hear 19 kHz though, if I use insane playback levels for single 19kHz simple tones.
However, this is not useful as at those levels I'm only damaging my ear/hearing more and not gaining any useful musical experience.
So to sum it up:
- home tests are not reliable, pro measurements more so (but even they have reliability issues after 11kHz)
- if you are interested, get your hearing tested by a professional audiologist, pays off
- don't try to play back test signals at loud volumes (even if it doesn't _sound_ loud to you): you will only hurt your equipment and your hearing
Play safe.