As loud as you want it to be. It's called the radio. Modern engines are quiet. I think some reefers make a lot of noise, but it's the kind of noise that actually helps me to sleep.
Its actually quiet in the cab when the windows are rolled up.Truckermario the newer Reefers are quiet. Its the older Reefers and some of the APU's like rigmaster that make a lot of noise.
it depends on the truck and how it's equipped. My '00 Mack was quite loud inside, very little sound deadening on the floor or the walls. My '09 Mack is very quit, but the sound/heat deadening on the floors is 3.5" thick, at idle, there is nominal engine noise. Under load samething it's very quiet, even jaking down a hill at 1800 rpm's it's still not very loud inside, general road/wind noise is more then the engine noise.
When my 550 hs is pulling up hill. Its very loud. but then down the other side, Well. I wonder if it is running! I play my Classic country, Southern Gospel and Right wing radio louder though.
A lot will depend on the integrity of the truck. There is a tremendous amount of wind noise out there. If you have a truck that has bad door gaskets or window seals it can make for a pretty bad wind noise. And of course if the truck has ever been wrecked and not put back together right, you will also get a lot of wind noise.
Not to mention if the truck has straight pipes without mufflers, just like a harley with straight pipes but deeper more resonant & smoother sound.
