"Vocal support" is a phrase used to describe when someone expresses their approval, encouragement, or endorsement of someone or something, typically by speaking up or using their voice.
No one gets anywhere truly on her own, and it often happens faster and better with vocal support from others. (mom2.com)
Best way to protest is to withdraw vocal support and stay totally silent for 90 minutes. (justarsenal.com)
Second, a factor that became important in the late 1980's was strong and vocal support from some segments of the environmental community. (robertstavinsblog.org)