I was wandering if someone could give me some exercises for singing low notes cause I've been having trouble sometimes I can hit a Bb1 and then I can't I just turned 15 and for alittle info my voice started changing at around 10-11 years of age shouldn't it have settled by now?
Firstly, Bb1 is very low note to be able to sign at any age; there any many people who can't. If on a 'bad' day you can hit C2, don't sweat it - you'll still be a very useful singer to have around! Secondly, your singing voice will probably change quite noticeably from year to year for at least another five years, and by smaller amounts thereafter until at least you're in your 40s. So don't worry about it not being 'settled'. Thirdly, when singing low notes, always relax never push things. Those bottom notes will never be as loud as higher up your range, so accept that and focus on a nice, sustained tone.
As for exercises, my suggestion is this: once your voice is warmed up, sing down the scale and find the lowest note you can sing today. Then sing one note higher, aiming to a long, sustained 'ah' sound or similar, at medium volume. (This also doubles as a breath control exercise). Do this for a while, then try the note below. If it's comfortable, sing that as long note, then go back to the one above. (If not, then don't sing it!). Alternate back and forth until you can comfortably sing the lower note. Then repeat :-) Over time, you'll build up the muscles needed for the low note. Remember: you've got decades of singing ahead of you - don't expect to get it all sorted this year.
Hope this is useful. Keep singing!