The word “Selah” is used over 70 times in Psalms and three times in the Book of Habakkuk. From what I've studied, it seems that it is a musical interlude or transition. The Hebrew word for Selah is celah { seh’-law}; Strong's #5542. It means “to lift up.” The expression seems to mark a climax in the music in which the singers and musicians are to “lift up” their praise to God.
When I visited Peru several years ago, on a mission trip, one of the things I was amazed with was the singing in the churches we visited. When those people sang, they really sang out. They didn't yell, they "sang out." Oh how we need to lift up our voices of praise to the Lord. I don't think that means we need to "yell" when we sing. I've been in services where the people who were singing were literally yelling the words; as if God were hard of hearing. I've been singing for over 30 years. In all those years I've never seen the need to yell so the Lord can hear me. Some may think it is more spiritual; maybe they think it makes them look more spiritual. I'm not trying to be "overly" critical, but if the Lord has given someone the ability to sing, they need to be good stewards of that ability.
A few years ago my son had nodules on his vocal chords. We went to a specialist that taught him how to and how not to use his voice. Most people may not realize it, but you can actually abuse your vocal chords by talking too soft. Of course you can also damage your vocal chords by yelling. Isn't God's design of our bodies amazing!?
I guess what I'm getting at is that we need to lift up our voices to the Lord in a way that honors and glorifies Him. My thinking is instead of yelling to the Lord (or whispering for that matter), we should lift up our voices unto the Lord and PRAISE HIS NAME!!
"Speaking to yourselves in psalms and hymns and spiritual songs, singing and making melody in your heart to the Lord;" Ephesians 5:19