There are different ways to lip buzz and each one has a purpose.
If a player has a issue with open chops, very airy tone all of the time….. then buzzing 2nd line G and up helps them fix that and builds lip muscle.When I see people with this problem I tell them to buzz for a few minutes a day for 2-4 weeks to fix it and then STOP.
This buzz should ONLY be done if you have a problem or for 5-15 seconds a day to find your embouchure.
This is a moderate buzzing fairly loud sound and NOT a squeaky uncontrolled poot sound.
The poot sound (where they tighten their face and seal the lips) has NO value at all for trumpet playing and yet many think that is a buzz.
The buzz that we use to relax, stay centered and can be used all your playing life is more like a kid doing the raspberry. It is loose, open, relaxed and can be done ALL day because you don’t tighten ANYTHING to do it. Most players have never done this because they interpret words like buzzing with other words they hear in the 6th grade like tighten up. Those NEVER go together.
This buzzing is from Low C DOWN to double Pedal C and is done from a resting facial position. You just spit and keep blowing air.
See my lip buzzing videos here: http://www.bbtrumpet.com/videos-and-audio/