Make sure the insulation on the inside of the dog house is in good shape. Does the doghouse seal well?
Make sure that you don't have an exhaust leak.
The only time the engine is very noticeable in my rig is when the fan clutch engages. (loud fan sound).
My rig was much noisier before I re-carpeted the cockpit and put down heavy padding.
If you want others to be happy, practice compassion.
If you want to be happy, practice compassion - The Dalai Lama
1984 310 Limited Motorhome
Courtesy Parking (W/S/E/Wi-Fi) on I-5 in Northern California, 70 miles from Oregon border