Higher is to lower as upper is to ... lower?
I asked a question on Quora about why the human voice has a lower volume limit. Like, you can't speak at as low of a loudness as you can whisper.
Here's one answer:
A "lower volume limit" in comparison to WHAT? Can you be more specific, please?
I used "lower limit" to mean "the least you can go," but the answer understood it as a comparative adjective (as such in "A has a lower Stack Overflow reputation than B").
"Bottom limit" doesn't sound right. What're unambiguous alternatives to the word "lower" in this context?