How to describe making sounds with your throat?
Grunt
"She made a grunt of assent"
1. "Uh–huh" (open mouth)
interjection \two əm's or two ən's separated by the voiceless sound h; ˈəⁿ-(ˌ)həⁿ, (ˌ)əⁿ-ˈ\
Definition of UH-HUH
—used to indicate affirmation, agreement, or gratification
http://www.merriam-webster.com/dictionary/uh-huh
2."Mmm-hmm" (closed mouth)
Guttural
adjective
- of or relating to the throat.
- harsh; throaty.
- Phonetics. pertaining to or characterized by a sound articulated in the back of the mouth, as the non-English velar fricative sound
"She made a guttural reply"