Don't believe there is. It an On or Off kind of thing. It's supposed to imitate the sound of a switch. You may be able to find a 3rd party app that would replace the lock screen entirely that has the ability, however. I have never looked to know.. I don't see my lock screen long enough to care and have the sound for it toggled OFF. But natively, I do not think there is a way to change the unlock sound.
Alright, well I'm going to go on a bounty hunt for an app that does the job. If I'm successful in finding one, I'll repost with the link to it, and mark it as the solution.
One of the first things I do on all my Android devices (which happen to all be Samsung products) is to ditch the TouchWiz launcher with Action Launcher 3.xx many use Nova, but that and either GBoard or SwiftKey to replace the keyboard and get a hex black going to conserve on battery since the Super AMOLED panel uses nearly zero juice.
Just wanted to toss that in there since you seemed new to the S7