The only real difference between what you call vocal noises and regular interjections (such as "Well well", "Wow!" or "Ouch!") is that these vocal noises do not fit into the phonology of their language, usually for one of two reasons:
They use sounds that are not inside the phoneme inventory of the language, such as "tsk tsk" which is actually a dental click (a sound that exists as a perfectly normal phoneme in many of the native languages of Southern Africa, but not English).
They use existing phonemes, but combine them in normally unacceptable ways (in linguistic terms: in ways that are incompatible with the language's phonotactics). The English "shh" use the perfectly normal English phoneme /ʃ/, but it used irregularly, since English doesn't normally allow words composed of consonants alone, without any vowels, and also since the consonants /ʃ/ is usually very prolonged.
If we choose to use this criterion to distinguish between "regular" interjections and "vocal noise" interjections, then あらら is definitely a regular interjection: it's a completely normal word as far as its phonology goes: it doesn't have any strange sounds or phoneme configurations. It's really not different than the English "Wow". It's probably an onomatopoeia if that's what you mean, but for the record so is わんわん, どきどき、旗 (originally:
[pata], cf. ぱたぱた, the modern onomatopoeia for flapping) and probably even 光 (originally:
[pikari], cf. ぴかぴか, the modern onomatopoeia for shining things).