Sneezing and making a whistling breathing noise?

[loveleavesascen]

My chicken is about eight weeks old. It's always had a little bit of a sneeze a few times a day. I think it could be because I live in the city and a lot of dust gets in. However, a few days ago I've noticed that it makes this sound that almost sounds like whistling. It isn't all day but it comes here and there. It is really hard to describe; a whistling noise is the best I can do to describe it. I'd record it but she does it so sporadically and it happens so quickly that it is hard to record. It almost sounds like a really weak trumpet noise, or a non high-pitched whistling noise. It would do its normal chirp and then itd go a little lower. Does anybody have any ideas? I will take the chicken to the vet if people think that it is a huge issue. I didn't know whether it was a probable respiratory problem, something common, or whether the chick was perhaps going through voice changes. I am unsure of the sex right now so I don't know what is normal either for this chicken.