the volume compression is more in 3 cylinder than 4 cylinder. this is because to meet more power generation to meet 4 cylinder engine power generation. during this more blast sound will generate inside the cylinder due to more compression volume and that is to at a time two cylinder. so more noise.
Are 3 cylinder engines noisier?
It is not that 3 cylinder engines are noisier, the difference in the sound occurs due to a different firing orders than a 4 cylinder engine. Traditionally, a balanced 4 cylinder engine will fire one of the cylinders after every 90degree rotation of the crankshaft.