Ask HN: Why is the default audio volume 100?
Almost all volume controls start at 100% by default. Whose idea was that? By the logic of volume regulation, it will certainly be too loud.
100% probably means "as stored or received" l. Most sounds provided will be adjusted to be somewhat inside the ceiling before you get distortion. But perceived volume is dependent on many things like frequency. And audio compression, where volume peaks are lowered to allow the whole thing to be made louder is often used for ads, so they sound much louder.
most people don't care. they may or may not be able to perceive a difference. they want a "hear better" knob and this is what they have so they assume that's what it is.