If the battery is the flooded cell type, make sure there is enough distilled water in each cell of the battery.
Also, double check the polarity of the harness on the bike.
I cannot say there is something wrong, as I have never heard any of my batteries make any noise while hooked up to the exact same charger you have.
Also, it is never really quiet in my shop, and I'm somewhat deaf. Just ask Susan. She says I never listen.