Out of roughly 1000 video clips I have online, no more than maybe 10 have audio. In each case, I felt the video was useless without the audio, and in each case I included " - with sound" in the title and description.
All those clips were accepted on all agencies I have submitted to.
If the audio is not really critical to the video, then drop it and export "video only." If it really and truly is needed for the video to be useful, then state so in the title. That seems to carry a lot of weight. (as another example, I have submitted photos with "blurry xxx in background/foreground" and had the photos accepted, where they had been rejected until I adde that to the title)