Amplitude & Loudness: Height Decides Size
How high the waveform "surges" is amplitude — the larger the amplitude, the louder the sound.
Say "ah—" softly and then belt it: the difference is amplitude — the air is pushed with more force. Loudness is measured in dB (decibels), a logarithmic scale — multiplying amplitude by 10 only adds 20 dB. This matches how our ears perceive loudness (it is not linear).
Experiment 3 · Amplitude & dB
Drag the amplitude slider: the waveform height changes (visual) and the volume changes (audio). Try "halving the amplitude" and listen — does it only sound a little quieter? That is why dB is useful.
Amplitude decides loudness, and dB is the auditory language of "doubling/halving". Many app parameters (H1−H2, SPR) are expressed in dB because that is exactly a measure of "relative strength".