Early prototype voice clips extracted from the PS3 port of Mass Effect, though they should be present in the 360 and PC version. I thought these were unused but as pointed out in the comments, these actually can be heard if you stand next to the bar counter at Flux.
"Walla" is an acting term used to refer to the murmur of background characters in a scene. The end of this video shows a human example of this extracted from the same file. These are meant to be played in the background when walking around a bar, not sure if that was always the intention or if its reused from an axed KotOR style dialogue system where most aliens speak their native language.
The filenames show which voice clips belong to what species. The non-human species sounded very different early in development.