How to Improve the Acoustic Level of the Generator Without Modifying It

There are alternatives to Silengen…
But they suck.

Starting from this self-referential but absolutely true point, let’s review the various solutions you can adopt to improve the acoustic performance of a silenced generator without modifying it.

First, it’s important to emphasize that you should not modify the generator. I’ll explain why with a simple and already solved equation:
x: damage to things and people = DIY modification: loss of certification
x = damage to things and people * DIY modification
loss of certification
x = prison

Let’s address technical topics with irony and lightness; however, modifying a machine can truly pose dangers to people and property. This isn’t a disclaimer from a YouTube video preview, but genuine advice to avoid trouble. Many people attempt to modify generators in an effort to make them quieter, leading to fires and serious damage.

The first important system for improving the sound level starts with the installation of the generator. This aspect—how to improve the acoustic performance of a generator—has been thoroughly addressed in the book “The Quietest Generators,” specifically in the chapter “The Secrets to Installing Soundproof Generators” on page 136.

Many believe that being qualified to install a generator means knowing how to position it perfectly level and connect it according to the provided wiring diagram. This is important, no doubt, but it’s the technical foundation, not the pinnacle of technical skill. Initially, there are technical evaluations often based (unfortunately) on choices by designers who are not sensitive to the subject, placing the generator wherever there is free space.

Let’s outline some important aspects to absolutely avoid when installing a quiet generator:

• Positioning the generator against a wall or, worse, at the intersection of two walls. In general, architectural barriers have a considerable impact on acoustic performance and the direction in which sound waves will be reflected. If you think placing a generator in a corner as if it’s being punished is a good idea, you’re about to make a mistake.
• Positioning the generator on a concrete base that is not adequately sized and, in any case, on a fragile surface. (It may seem absurd, but a surface of mixed inert materials with self-compacting concrete can yield better results, provided it is stabilized with adequate supports.)
• Wind matters. It’s now easy to retrieve wind statistics for a specific address online for free. An installer will do everything possible to avoid placing the generator facing the wind relative to the serviced building.
• Installing the soundproof generator inside a technical room that was not designed for a generator. This is a topic I am particularly passionate about because it is a very common condition.
  If you purchase a generator that has a hot air discharge grill measuring (for example) 80×40 cm, how do you expect air to exit the technical room through a window facing outside measuring 50×40 cm? What physical phenomenon should cause the air to channel there and not re-enter the generator through the intake openings?

We’ve seen that installation plays a fundamental role in noise propagation; now let’s look at two more tips that can be adopted to improve or try to condition acoustic performance.
Don’t think I’m crazy for the clarification I’m about to make: I want to specify that I’m writing these tips on September 27, 2024, even though I’ve partially discussed them in my book, so when someone tries to sell them to you as their own or even as a research and development subject, you’ll know they’re a fraud and don’t deserve your money.

Soundproof panels. Provided they are covered with self-extinguishing material (not egg cartons as shown on some YouTube channels), a panel positioned about 2 meters from the sound source can limit propagation in that direction. It’s essential that the panel does not vibrate in any way; otherwise, you’ll get the opposite effect.

Limit air chambers. Silent generators typically have a structure such that their supporting frame is supported by four “feet” or “pads” or by two beams arranged along the length parallel to the engine-alternator assembly. Both structures share a characteristic: they create an air zone under the frame between the bottom of the generator and the floor. If you measure the acoustic pressure at that point, you’ll notice how uniform and powerful it is, but most importantly, what makes a difference at that precise point are the frequencies.
The Silengen is designed with a frame that perfectly adheres to the floor, balanced to vibrate as little as possible.
Thus, a suggestion is to apply material, as long as it is self-extinguishing or better yet fireproof, to prevent sound waves from passing between the floor and the steel base on all four sides of the generator, avoiding the annoying “guitar effect.”

Fill it up. Yes, you read that right. If the tank of your generator is metal and it’s placed on the base, i.e., on the bottom of the generator, then it’s better to keep it full.
Those familiar with physics concepts know that sound propagates better in a liquid than in air; therefore, the advice to keep the tank full seems contradictory. However, it is not for a specific reason that I will now explain.
A metal tank when empty or almost empty vibrates more than a full tank. This precaution allows for minimal results in a small tank of 50 or 100 liters, but when working with large capacities necessary for long runtimes, a tank of 600 or more liters can make a difference.
Have you ever received this advice?
Write it in the comments!