I own a CM311 that's approx. two and a half years old. I always use the mic utilizing the 9 volt battery, since the phantom power on my band's board activates all channels, instead of just mine. Anyway, I installed a new battery(duracell) about a month ago and only use the mic once a week. It was working fine until last night when I noticed that the mic was not as loud at the same volume setting on the board. I did purchase and install a new WS-6 wind screen, but don't see how that would be the cause. The old one was a little degraded, so the new one should improve clarity. I haven't tried a new battery yet, since the one in there is practically brand new. However, I will install a new battery first just to see if that's the culprit. But I've never had ths type of problem as a result of a weak or defective battery. Every Duracell 9 volt that I've used has been reliable for much longer than 1 month. Any suggestions? - Thanks!