Diesel Generators are notoriously noisy pieces of equipment, after all they are a prime example of heavy machinery with moving components fuelled by the power of diesel causing explosions in an engine.
Airborne sound is energy and is measured in decibels (dB). In this scale the every three dB increase measures a doubling of the energy. People however are not very good at detecting this level of increase easily therefore a better way to interpret the scale is to say that a ten dB increase equates to a doubling of the perceived noise.
Diesel Generators can range massively in noise levels from 65dB up to 110dB. This depends on many factors, including but not exclusively, the engine type, size and configuration, the radiator, the quality of insulation, the presence of anti-vibration mounts. The level of load being applied to the generator itself has a substantial effect also.
A quiet rural area would see a noise level of about 30dB, whilst background noise and conversation in a restaurant would be in the region of 60dB. A pneumatic drill would be in the region of 100dB.
There is a substantial range of differences in noise depending on the specification that you are to purchase.
A diesel generator offers back up power solutions by converting chemical energy into electrical power. This process involves the use of a diesel engine working at 1500 or 1800 RPM.
There are numerous causes of noise in a diesel generator.
- The Engine itself is driving the alternator by creating a rotary motion through hundreds of explosions. The combustion nature of an engine causes the vibration and resonance of hundreds of small parts within the engine.
- The burnt fuel is discharged from the engine as exhaust fumes, whereby the engine is drawing in air and pushing it out into the atmosphere in large volumes at high pressures. The noise of a combustion force can be thousands of Hertz.
- The outer surface of the engine and accessories can vibrate, as every part of the diesel engine and alternator get equally excited once the engine is on.
- The rotation of the radiator fan to assist with cooling.
Diesel Generator manufacturers, like Welland Power, put thought and design into compensating for these causes, in a bid to reduce noise successfully but also economically.
After all noise level is one of the major considerations that is given by a customer when selecting their generator. Some generators are supplied as open skid mounted diesel generator sets, whilst others are supplied with sound attenuated canopies.
It would be expected that an open diesel generator set, will be positioned in a generator room or house, whereby the room itself will be sound insulated. This is perhaps the best solution to reducing noise, however not always practical or affordable. The alternative is to have the diesel generator supplied with a sound attenuating canopy.
Soundproofing is achieved in numerous ways.
Firstly, by adding mass to the structure sound energy is reflected and converted into heat by the mass of the new structure. Welland Power Diesel Generators are supplied with optional sound attenuating canopies. These canopies are constructed from 2mm British Mild Steel.
Other companies may offer canopies with thinner sheet metal, with many offering 1.5mm steel, which will have a negative effect on both strength and noise reduction. The thicker (larger gauge) the steel is, the more reduction there will be, and more crucially the more sturdy the canopy will be.
The main reduction from the canopy however is achieved through the lining of canopy with specially designed sound insulating foam. This sound insulating foam is positioned on as much of the inner surface as possible. The generator canopy designers specially calculate the amount of ingress required to maintain air flow, whereby the less gaps there are for sound waves to escape freely the better. The acoustic foam is open celled and works by reducing the amplitude of sound waves. This foam is available in different sizes, colours and thicknesses.
Importantly the diesel generator is mounted on a solid base with anti-vibration mounts. This decouples the diesel generator from other structures to prevent the sound vibration from travelling
Another noticeable reduction in noise is achieved through a suitable exhaust and silencer. All Welland Power Diesel Generators have silencer and exhausts included. For small diesel generators they are complete with a modular silencer built into the base for canopied diesel generators or have tubular silencer for open specifications. The gas and subsequent sound waves omitted noise from the engine pass through the silencer and exhaust system before dissipating into the atmosphere. In passing through sound waves are absorbed by the insulating material (rock wool and steel) thereby reducing the noise levels audible externally. A standard silencer brings about a reduction in the noise level by approximately 20 dB(A). This is considered the industry standard for a residential silencer, whereby industrial standard is even quieter.
Welland Power develop a range of canopy specifications. The positioning of the diesel generator in relation to buildings and people is crucial, whereby air flow is important to be considered. It also would not make sense to install your generator outside your bedroom window. The industry standard is to consider sound levels at 1m, 7m and 15m distances. A standard sound level at 1m for a canopied specification is circa 75 -85dB @1m. The larger the set, generally the noisier they are.
A variety in degrees of noise reduction are available, whereby design and manufacturing can achieve a wide range of possibilities. As most projects and specifications are dictated to by space and budget a modest sized canopy would be used typically. The benefits on having a larger canopy would be the ability to encase the generator in thicker sound attenuating material, whilst not affecting the air flow. Should a project have requirement for a greatly reduced noise level, this can be assessed.
Depending on what the requirement is there is scope to build special enclosures or containerize the diesel generators, whereby the walls can thickly padded with sound insulation.
Cover photo credit: YouTube
