CS4 Dissapointment

I have been running Coopers CS4s for about 8 months now and have been very happy with them till now. After putting 10K miles on them I have noticed the road noise has gone up significantly to such a point that I have to comment on them. The road noise is so bad we thought a wheel bearing was going out but they are fine. Transmission is fine.... this leaves the tires which is very frustrating for I picked them from another brand due to the lower road noise. If this continues I will have to buy 4 more tires for these things are becoming very very loud.