Set your device to a very high volume and use the 0 dB row (highlighted) as your reference.
Warning: the positive +dB rows can then be very loud.
First select 1000 Hz and adjust the top slider so that you can just barely hear 0 dB.
At the same setting, you should not be able to hear −5 dB at 1000 Hz.
Then compare other frequencies: try 0 dB first. If you cannot hear it, click higher +dB levels.
If you hear it easily, test the −dB levels. Note: a typical hearing range is about 20–19,000 Hz for young adults and about 20–8,000 Hz for older adults.
Also, some playback devices cannot reproduce frequencies below 100 Hz or above 15,000 Hz, so missing tones may be caused by your device rather than your hearing.