I have discharged centerfire rifles and revolvers toward quite a few bears over the years. Generally those which are some distance (≥ 100 yards) will gladly make tracks and skidaddle. OTOH, those which are ≤ 20 yards will often only glare. (These are bears that don't have much human contact FWIW.) I have no faith in noise to deter bears (unless I am actively trying to approach them crazy .)

I don't carry anything other than what's in my head along with some type of weapon (firearm) I can shoot well. When bears need to be scared away after they have gotten too close, I like to shoot the rock nearest to the bear. Bears are rarely unimpressed by splattered high speed bullet fragments and rock shards.

Sometimes, the air you 'let in'matters less than the air you 'let out'.