This one is my fault; someone on Nexus alerted me to the fact that the horse animation fix I provided a few years back caused Arvak to stop making any sound except for the footstep sounds. Tested on a totally vanilla save to confirm that Arvak is supposed to make other horse sounds, and with USSEP and the updated animation files Arvak only makes footstep sounds and no others. Attached the fix.

Attached Files:
Arvak Sound Fix.zip