Sound at Low Volume: Why Quiet Changes What You Hear
Short answer: Your ears are less sensitive to very low and very high sounds than to the middle, and the gap grows as the volume drops. Turn anything down far enough and the bass fades first, then the sparkle at the top, and what is left sounds thin. Nothing is wrong with the speakers. It is how hearing works.
What happens when you turn it down
Hearing is not even across pitch. We are most sensitive between about 2 and 5 kHz, the range of a raised voice or a baby crying, partly because of the shape of the ear canal. Low sounds need more energy before we notice them at all.
At high volume this hardly matters, because everything is well above the level where it becomes audible. At low volume the quietest parts drop below that level. As one description puts it, music becomes thin sounding at low volumes, losing bass and treble. The "loudness" button on old hi-fi amplifiers exists to push those ends back up when you listen quietly.
Why this matters for background sound
Background sound is played quietly. That is the whole idea. So it gets heard in the conditions where bass is weakest and the middle dominates.
I ran into this with my own project. An early version of the Space world sounded thin and sharp, and it was worst at the low volume I use for working. It was made of thin, high tones with very little underneath. Turning it up made it fuller, but nobody wants background sound loud.
What fixed it was changing what the sounds were made of. Everything moved lower, and each note got a quiet layer an octave below it for weight. I wrote about that layer in The Sub-Octave: Where "Deep" Comes From.
What I took from it
- Judge a background sound at the volume you will really use, not at the volume that flatters it.
- If something sounds thin when quiet, turning up the bass on your device helps more than turning up the volume.
- Small speakers make this worse. A laptop or phone can barely produce low sound at all. See Headphones vs Speakers for Ambient.
Sources
- Equal-loudness contour, Wikipedia: where hearing is most sensitive
- Loudness compensation, Wikipedia: why sound thins out at low volume
Try it: play Ocean on headphones at a low volume. It sits in the low register, so this is a fair test of your setup. It is free and starts in one click.
Open Ocean, free