I saw yaks last week for what I think was the first time. At least a lot of them together; I imagine I've seen a few at a time before. We ate our lunch with yaks roaming the hills behind us. We were at around 11,000 feet.
Yaks don't sound much like cows, even though they don't look too different from cows. They sounded like they were sighing and moaning instead of mooing like cows. Of course, if I hadn't heard cows all my life, they'd probably sound pretty strange to me too.