low volume in earphone

hi all,

i have a issue of while hearing music in iphone 4s its sounds very low i'm dam sure its not the problem with earphone because i tried with many branded earphones like bose,beats and also with sennheiser.....

pls some one help out this whether this is a hardward problem or this is the normal volume level of iphone 4s.

my ipod 2g sounds good and louder than my iphone 4s