Vanilla end portals already have this. It might be interesting to have (empty by default) sound events added for other portals, both vanilla and modded, such that mod or modpack makers can apply sounds for opening (and closing; #607) portals at will.

As mentioned prior, the sound event for opening a nether portal would be completely blank and silent, but still there, as would creating mirrors or portal helper portals (which would require two more distinct sound events respectively).

It's being considered