Crackling heard when using Twilio Elastic SIP with FreePBX

It does sound to me like a timing issue. What is the physical hardware vmware is on? Is it ESXi or workstation? Server class hardware, pc class, or other questionable hardware? Perhaps following the tips here about kernel timing could help

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1006427