Advice worth listening to

While kW output and fuel type are major considerations, noise is one of the next top priorities in any decision making when specifying a genset. Ongoing exposure to it in the workplace can help contribute to stress and ill-health, while long periods of exposure can even result in irreversible hearing loss. High noise levels can also make communication between work colleagues difficult, or in some case impossible, increasing the likelihood of accidents.

In the UK, there are no blanket standards for the amount of permissible generator set noise. Each application is different, and every planning authority dictates what is required. Noise levels can also vary significantly based on generator size, fuel type and manufacturer. A 50kW diesel generator set can produce around 85 dB(A), which is as loud as a petrol lawnmower, while a 1500kW engine can be as loud as a jet engine 1,000 feet in the air at 105 dB(A).

Several noise sources have to be taken into consideration, as well as sound that is generated from the movement of cooling air when a generator is placed inside an enclosure or building. A number of tactics can be employed by operators to reduce noise, and many can be used together to help significantly reduce overall levels.

Bad vibrations

Inertia bases provide an ideal vibration and noise isolation solution. Designed to support reciprocating equipment, when used in conjunction with an acoustic isolation system, they are an effective anti-vibration technique for machinery. A concrete-filled frame, for example, can be used to provide inertial mass, which muffles vibration and lowers the centre of gravity, thereby reducing movement.

Keep site layout in your sights

The easiest way to reduce the effect noise has on an immediate workforce and surrounding communities is to increase the distance between the operations and the source. If a generator is moved further away, the energy is spread over a greater distance and, as a result, has less acoustic intensity. A general rule is that if distance is doubled, a 6dB noise reduction can be achieved. It is also important to note that the term ‘free field’, which describes where sound freely propagates and spreads uniformly, does not begin until 30-50 feet away from the generator.

Think ‘inside’ the box

Enclosures can be used to reduce engine noise. Typical sound attenuated generator enclosures are typically steel-framed and consist of panels that are multi-layered composite, treatments comprising of an impervious exterior layer and a section of porous sound absorption material facing inwards. The main absorption layer is impervious, which blocks the passage of sound energy radiated by the enclosed source of sound from the generator. The porous sound absorbing lining will dissipate the retained sound energy.

Get the specification right from the start

Good acoustic design must be considered early on in the planning process to ensure that the most appropriate and cost-effective solution is identified. Most laws are tougher when dealing with prime or continuous power applications because of their extended use of operation. If a particular noise level at the property line must be achieved, then any sound attenuated enclosure manufacturer should be told beforehand what the requirement is and how far the enclosure will be from the property line. The onus is on the supplier of equipment to meet specified noise levels.

Noise is becoming more of an issue for plant operators because of health and safety regulations, industry growth, and a rise in the number of residential areas encroaching onto ‘brown field’ areas. By taking these steps, decision makers can help ensure that they are installing a generator that is fit for purpose, emitting a noise level that is appropriate for the surrounding area.