A very valid point that nobody else raised yet, most of the noise from a cheaper generator does not come from the exhaust, it comes from the vibration of the metal. Larry
I haven't heard this one before. Another thing that makes a difference is how the generator is cooled. Air cooling, especially those that are cooled by a built in fan, are noisier than water cooled version of the same size and type.
While I agree with most of what you stated in your post I do not agree that fiberglass is the best insulation except in high heat, or relatively quiet environments. There are many things that offer better sound insulation than fiberglass. One is foam board, but the best I have ever used is a sandwich of two types and densities of foam with a layer of lead sandwiched between them. It dramatically reduces the noise in a generator compartment, where fiberglass does not come close to doing the same job. It is called lead-lined foam, and I doubt it is available in the Philippines, but it is available in the U.S. After experimenting with insulating a large number of generator enclosures for R.V's, I have found fiberglass insulation is the cheapest and does the worst job, no matter what the density of it is. Next is foam board, such as blue styrofoam which is very dense, or white styrofoam which can vary from being soft to moderately dense. What works well with foam board is to use multiple layers of various densities as each density absorbs different wavelengths of sound. The best, and most expensive is engineered lead-lined foam. Using this and sound baffling the air intake vents for the enclosure coupled with a good quality exhaust system will cut the noise of a generator dramatically.
yes that's what I meant in that environment, heat, gasoline, oil, combustible. fiber glass is cost effective, also there is an acoustic fiber glass available, not sure if you can get it here, I used it in internal walls in my house in AU , also if you wrap the exhaust pipe with a heat tape a bit like asbestos it can transfer up to 70% of the heat outside of the box, I use to use this on extractors on hot rods to remove the heat from the engine bay and around the foot well.
Think about it, an aircooled engine has many cooling fins which cool the engine as air is directed across them. These fins vibrate. When metal vibrates, it makes noise. On new engines you will often find bits of rubber between the fins, this is to help with the vibration/noise issue. A liquid cooled engine has a water jacket surrounding the cylinder. In addition to cooling, it is an insulator against noise. Most any motorcycle enthusiast will tell you a liquid cooled engine is generally quieter than it's air cooled counterpart. Cheaper generators have a metal frame and sheet metal around the entire generator. This often is the source of much noise. Better built units have their own insulated box to deaden noise and vibration. Generac builds many different grades/prices of generator. Often the lower grade unit has the same engine/alternator and exhaust as the higher priced and much quieter unit. The difference is in the cabinet.
