actually, thats not quite true. you can speak to your dog in all levels of rally.
novice is done on leash entirely, and you can both talk and do things like clap, tap your legs, etc. you CANNOT touch the dog at all.
in advanced and excellent (the two next levels) you can still talk to your dog. all work is done off leash.
from the AKC regs:
" handlers are permitted to talk, praise, encourage, clap their hands, pat their legs, or use any verbal means of encouragement. Multiple commands and/or signals using one or both arms and hands are allowed; the handler's arms need not be maintained in any particular position at any time. The handler may not touch the dog or make physical corrections. At any time during the performance, loud or harsh commands or intimidating signals will be penalized."
Kim and Bowie's Modern Love, RN, CGC, SND