Hi.

Water noise or metallic noise needs meticulous investigation. General call quality issues can be checked as below.
1. Check if AMRC switch is ON at RNC algorithm switches, if yes, then ensure RSVDSWITCH0_BIT9 is set to 1 (More of a Silent call solution for UEs checking TB Size)
2. For CS calls routed through the transcoder TCDR, codec conversions will always degrade MOS by about 0.1. to support TCDR, set IUUP_V2_SUPPORT SWITCH=1 in UCORRMALGOSWITCH
3. Packet loss during transcoding or due to IP switching capacity insufficiency can lead to metallic noise.
4. Cell uplink load > 99%, with default equivalent user number ENU and without any load balancing strategies could lead to sharp intermittent noise during voice call
5. Other RF basics, clear all co or adjacent channel interferences by quality AFP

i hope this helps.
should you need further support on real time troubleshooting, mail me: ralphobafemi@gmail.com
I'd be glad to support.
##Pls vote if this helps.