Set the difficulty to Easy and direction to Boost. Press Play, then use Space/D to toggle between A (original) and B (level-shifted). Your job is to identify how many dB louder B is compared to A.
Click the answer that matches what you hear. As you improve, reduce the difficulty to train your ear on subtler level differences. Enable Both directions once you're comfortable identifying boosts — cuts require the same skill but in reverse.
Level differences are purely about loudness — not tone, not timbre. The signal is identical on both sides; only the volume changes. This makes it a pure test of your gain perception.
A useful rule of thumb: 3 dB is just noticeable as a level change to most listeners. 6 dB feels meaningfully louder. 10 dB is roughly perceived as "twice as loud." Use these anchors to calibrate your guesses.
Avoid adjusting your listening volume between A and B — let the difference come to you naturally. Switching quickly back and forth with Space/D makes the difference easier to detect than listening to each side for a long time.