Stereo as Information: What Left and Right Can Tell You
Short answer: Stereo is usually talked about as width: a big, spread-out sound. It can do a more useful job, which is to tell you where something is. In my app each sound sits where its shape sits on the screen and moves when the shape moves. With your eyes shut you can still roughly follow the picture.
Width and position are different things
Wikipedia defines panning as "the distribution of an audio signal" into a stereo field "determined by a pan control setting". In plain words, you decide how much of a sound goes to the left ear and how much to the right. Equal amounts and it seems to sit in the middle. The same article says an early version of this was built for the 1940 film Fantasia.
You can use that in two ways.
- For width. Spread everything across the whole space so it feels large. It's pleasant, and it tells you nothing.
- For position. Put each sound in one place and keep it there. Now left and right mean something.
What I do with it
- A sound sits where its shape sits. A circle on the left of the screen is heard on the left. Drag it across and the sound follows.
- It moves smoothly. The position glides to its new place. It never jumps, because a jump in position is heard as a glitch.
- Near shapes spread wider. Shapes that are close to you are drawn bigger, and their sound is allowed further out to the sides. Distant shapes are drawn small, and their sound stays near the middle. So the same cue you see for distance, you also hear.
- Some things land somewhere in the field. In Space a whistle or a short run of beeps arrives from a different spot each time, far left, near the middle or far right, and then fades. With no walls to bounce off, where it lands is a big part of the picture.
The browser makes this simple. MDN says its stereo panner takes one value between −1, which is "full left pan", and 1, which is "full right pan". I feed it the shape's position.
Why it matters for background sound
I didn't do this for the effect. I did it because several sounds playing at once from the exact middle pile up into one lump. Give each its own place and they stay separate, even when they are quiet.
It also ties the sound to the picture. When something drifts in from the right, you hear it arrive from the right. I think that is a large part of why the app feels like a place and less like a player.
When it doesn't work
A phone's single speaker has no left and right, so all of this folds into the middle. Nothing breaks. You lose the positions and keep the sound.
Speakers and headphones also treat left and right differently, which I looked at in headphones vs speakers.
Sources
Try it: Open Ambient Sound Online with headphones on and drag one shape slowly from one edge to the other while it overlaps another shape. It's free. Then shut your eyes and do it again.
Open Ocean, free