Here we play some simple sine tones and your task is to identify the frequency of each tone.
The normal hearing range for a young person is 20Hz to 20kHz.
How high is really a tone at 15kHz? Can you hear it? If not, beware that many speaker systems and digital converters have a slight rolloff. It is not necessarily something wrong with your ears, but if the very high tones are inaudible, please try the test on another sound system, possibly also with another sound card.
Frequencies below 100Hz is also reproduced with significantly variable intensity on different sound systems. Spending time getting familiar with your sound system is valuable as a reference for all other listening you want to do on the same system, and to compare your current listening conditions with thos in another room on another sound system. The sine tone tests are not the only method of doing this, it can be just as valuable listening to a music signal that you are familiar with. The sine tones are good as a precse reference, as you can know exactly where in the frequency range your system has dips and boosts.