Originally Posted by trest1
Does anyone have any recommendations regarding products available for soundproofing diesel
engines. Our current
sound proofing is 12 years old and breaking down quite rapidly.
thank you for any assistance
Soundproofing has two main components. The first is airborne noise
and the second is structure borne.
is created by the intake and to a lesser extent by the exhaust
. Blowers also cause issues here. Airborne noise also leaks
out of gaps around the engine room. Sealing these gaps will make a noticeable difference. This is step one.
The majority of your powertrain noise will be structure borne. If you have any misalignment in your prop shaft, engine unbalance, collapsed or bound engine mounts or worn tailcase bearings this will transfer through the mounts.
Structure borne noise will travel and breakout wherever there is large unsupported structure. The sole, vertical panels
etc. Step two is to check for and fix any of the above issues.
Step 3 is to work out which frequencies are resonant for the rotating elements. Check alternators are not misaligned. You can also note at which engine revs the noise is worst. You might also find other parts
of the boat resonate. To change these resonances you can change the stiffness or mass. Stiffness is typically what we tune because mass of most things is fixed.
Step 4 is to apply constrained layer damping, aka soundproofing. The key here is to choose the soundproofing to change the resonance of the panel you attach it to. Ideally this resonance should by at a higher frequency than the source will be.
I applied the above 4 steps to our generator
which was exciting the aft bulkhead. I found that the engine mounts were misaligned and there were several gaps around vents and water
I reduced the noise (sound pressure) by 9 Db and eliminated the bulkhead resonance completely. Much quieter now.
Note that soundproofing would have had no impact for the above use case. You choose sound proofing based on noise attentuation at specific frequencies. This no such thing as universal soundproofing. Also note that there is no correlation between thickness and noise reduction.
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