Of course the Diesel emitts more noise. It is just a harder combustion with higher pressure

In petrol engines usually the air/fuel mixture is homogeneous and so it burns smoothly starting at the spark plug and ending at combustion chamber walls. On the other hand compression ratio in diesel engines is almost double that of the petrol engine and so high pressures are expected and the mixture is not homogeneous and so combustion is expected to start any where in the combustion chamber resulting in much higher noises.

And the answer is . . . . it depends.

While the diesel engine has indisputably the potential to create more noise (due to the somehow less controlled process of combustion and the fact that the same power is typically delivered with fewer rpms than with a gasoline engine), this is not necessarily true for all operating conditions regarding modern direct-injection systems:

• Most of the diesel noise has to be attributed to a non-constant increase in cylinder pressure during combustion.
• With pre-injection, multiple injections or control of the fuel flow rate during injection the pressure rise can be controlled such that the pressure rise is in good approximation linear. In this case a diesel engine can sound just like a gasoline one.

I implemented such things in the end of the 1990s, bringing the system into series production in 2000. This is not only possible with common rail but with any of the direct injection systems. Requiring additional efforts, but doable.

Regards

Diesel engine has more noise due to injection system and engine structure. 

Dear Khaleel

Diesel engines have higher noise levels due to the higher compression ratio they work by. Diesel engines works with 14 to 24 compression ratio while gasoline engines at 7 to 9.5 CR. This difference appears in the high pressure rates of combustion inside the combustion chamber. As a result the emitted noise from the CIE are higher thatn that for SIE.

Regards

Unlike petrol engine diesel engine's combustion starts some time late after start of injection. This time lapse is known as the delay period. The fuel injected during this period will have some time to accumulate and mix thoroughly with air and when combustion starts a very high pressure rise occurs during the period that follows known as  the premixed period and this is  what causes diesel engine noise to be louder than petrol engine's. In fact if the delay period is longer, very high noises and vibrations are expected, a phenomena known as Diesel Knock which is of course objectionable.

Dear all thank you for answers .

Diesel Engine operates more roughly and emits more noises.

Dear  Khaleel

There is no doubt that we are always on the rise of  diesel automotive noise and a lot  do not know the answer to this:

The engine that works with gasoline have ignition by the spark that occur through the spark plugs and therefore have ignition gradually. The ignition in a diesel engine is flammable self through the very strong air pressure accompanied with high temperature so then fuel injection at a temperature of certain self-ignition occurs kidney (ie explosion momentary happening inside the cylinder and is not flammable) for it to be the voice of the diesel engine is higher than gasoline, so the cars can always easily recognizable by her voice, even if not able to see them

There is another reason for the rise in engine sound is because of the great strength and the strength of its determination.

Regards

Diesel engine is noisier.

Diesel engine is more noisy beacuse it has an compression ignition and unlike petrol engine which has a positive ignition. In diesel it all depends on the compression and controlling the time of ignition is difficult + diesel is injected which in case of non atomisation can cause I abnormal combustion. Structure also adds up the noise.

Basically: diesel engine is more noisy .

But I think the engine noisy dependent on :

1. Engine age

2. Types of used fuels ( ex. Hydrogen fuel or biofuel mixe with used fuel)

3.Engine speed.

4. Loading of engine.