How to Silence a Generator

How to soundproof a generator set in 4 steps.

One of the top 6 mistakes made when buying a generator is choosing an open frame generator over a quiet generator. However, it happens that for various reasons we find ourselves with a generator without a hood, perhaps because it is an “inherited” generator set or purchased second-hand.

What to do if the generator set makes too much noise?

Firstly, please note that open frame generator sets are not always suitable for outdoor operation.

The apparently best solution is to enclose the generator in a box lined with soundproofing material, but the temptation to do so must be resisted for at least two reasons.

Hot air, cold air…

When the generator is in operation, it “breathes”, that is, it draws in fresh air and expels hot air, therefore any box or bonnet must be specially designed and calculated in detail. Otherwise, the best consequence could be the rapid and irreversible failure of the engine or the alternator, the worst a fire that is difficult to extinguish.

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Security and Certification

Inserting the generating set in a box, in a bonnet, in any frame, be it self-produced or purchased from a specialized company, entails the modification of the generating set, therefore the loss of the safety requirements and of the relative certification, except some specialized technician is able to produce a technical file and issue a certification.

On the subject of safety, many convinced of being “smart”, in case of control by the authorities show a declaration of conformity relating to the “original” generator or the one in the open version, even though changes have been made such as that of the bonnet. The risk is high, especially in the event of an accident, some insurance companies hire expert experts to ascertain this type of irregularity and not pay the damages. Furthermore, the fault for damage to persons should not be overlooked, in the event a worker is injured or worse, loses his life due to an accident involving the generator set.

For those thinking that there are no differences between the safety conditions of the machine and those of the same after the modification, it is good to remember that the differences exist and are also important. The refueling conditions, the emergency stop buttons, the discharge of the burnt gases, etc etc. (just to mention a few).

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Soundproof the generating set

However, with a noisy open frame generator set there are solutions.

In addition to the simpler one, that is contacting a specialized centre, modifications can be made to the room intended to house the generator set to make it as silent as possible.

It is much easier to operate on the premises that will comply with the regulations relating to the installation rather than work on the machine (the generator set) which must respond to specific directives.

  1. The first step is always to check the type of silencer the generator is equipped with. The exhaust silencer can have different levels of noise reduction, expressed in dB. Replacing the silencer is the first investment to make to get a result. If the back pressure is not modified and the connections with the pipes are maintained, replacing the silencer with a more performing one is not considered a modification of the machine if this was supplied with a separate silencer.
  2. Reducing vibrations is the second step to take if you want to contain the noise of the generating set. Usually only the frame parts, pipes and fittings vibrate. Often the pipes that go from the exhaust manifold to the silencer are almost always the ones to vibrate and generate the most noise.

Worse, however, when parts of the room used to house the generator vibrate. Doors, windows, extractor fans and even the floor itself vibrate when the generator is running, ending up transmitting all or part of the noise outside.

  • Convey and insulate the air intake and expulsion areas.

Sound moves through a medium, so in our case the air being expelled from the engine. Inside a room it is usually essential to convey the hot air towards the outside, and the latter carries with it the noise generated inside the room, it is therefore important to concentrate the soundproofing of the room in particular inside the conveyors that usually work as a sound box, amplifying it and making the situation worse.

  • Soundproof the walls. You cannot think of completely soundproofing a room by covering it with soundproofing materials, almost as if it were a recording studio, however it is good and right to install sound-absorbing panels (not soundproofing) in the upper parts of the room. The suggestion is always to install sound-absorbing material in at least 20% of the walls of the room.

The best defense is the offense.

The regulations on noise emissions have become stringent and will become more and more so in the near future. The advice is to avoid DIY as much as possible and rely on new and certified products.

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