I usually will make a short nasally "merrp".

However one time during shotgun season, a doe came running past my stand at 5 yards. There was a foot or more of snow on the ground so I never heard her until she was right below me. Startled, instead of giving her a "merrp" I started hissing at her! "ssssst, sssst!" I realized what I was doing, felt like an a$$ and immediately gave her a "merrp."

She stopped, walked back a few yards and then I gave her a slug.