While many municipalities did not have to worry about noise levels in the past, the increasing proximity of residential, industrial, and commercial areas has focused more attention on this issue.
Generators can be a significant source of noise, and the reduction of volume levels is critical to comply with local ordinances. In addition, the Occupational Safety and Health Administration (OSHA) has specific guidelines for workplace noise to ensure employee safety.
Therefore, an effective noise reduction strategy is a key element in planning generator installation and operation.
Sound vs. Noise: What’s the Difference?
Sound is anything we hear while noise is unwanted sound. To a degree, this distinction is relative. After all, one person’s enjoyably loud music is another person’s unbearable racket. However, more quantitatively, sound is measured by decibel (dB) units, and sound heard by the human ear – as opposed to the entire frequency spectrum above and below our hearing range – is measured using the dB(A) scale.
For the sake of comparison, here are some examples of typical dB(A) noise levels:
- Quiet Room: 40 dB(A).
- Lawn mower (3 feet away): 92 dB(A).
- Circular saw (3 feet away): 115 dB(A).
Sounds above 85 dB(A) are considered harmful, 120 dB(A) is painful, and 150 dB(A) can cause eardrums to rupture. In all these cases, prolonged exposure increases the risk of hearing loss/damage.
6 Main Sources of Generator Set Noise
There are six main sources of generator set noise with dB(A) measured at one meter:
- Engine Noise: 100-121 dB(A), depending on engine size.
- Cooling Fan Noise: 100-105 dB(A).
- Alternator Noise: 80-90 dB(A).
- Induction Noise: 80-90 dB(A).
- Engine Exhaust: 120-130 dB(A).
- Structural/mechanical noise: Varies, radiated as sound.
6 Tips for Reducing Generator Set Noise by Using Generator Enclosures
Strategies to decrease these generator noise levels include:
- Acoustic Barriers: Using steel enclosures plus sand- or concrete-filled walls to reduce exterior noise.
- Acoustic Insulation: Lining walls and air ducts with sound-absorbing materials to lower interior and exterior noise.
- Isolation Mounts: Installing flexible joints as well as mounting a generator on vibration isolators.
- Cooling Air Attenuation: Using baffles with air inlets and outflows.
- Maximize Distance: Placing equipment as far as possible from property lines. In an open area, every time distance is doubled there is a 6 dB(A) drop in noise levels.
- Exhaust Silencers: Utilizing mufflers (the same principle as a car exhaust system).
It’s important to note that no one method above can be used exclusive of the others. An effective noise reduction strategy will employ multiple measures.
Reduce Noise Levels Through Sound-Attenuated Generator Enclosures
One way to significantly reduce noise levels and comply with local ordinances is by enclosing a generator set with a sound-attenuated structure.
An attenuator is a device which allows a large amount of air to move through it while significantly reducing volume levels. Sound attenuation—the amount of noise being removed—is also measured using the dB scale. For example, Cummins diesel set enclosures are available in three levels:
- Level I: 70 to 89 dB(A).
- Level II: 63 to 78 dB(A).
- Level III: 68 to 70 dB(A).
While the differences between levels may seem small, the impact can be significant given how dB(A) is measured: 80 dB(A) – a freight train 45 feet away – is twice as loud as 70 dB(A), and 100 dB(A) – a jackhammer – is 16 times as loud as 70 dB(A).
There are some issues to keep in mind with sound-attenuated generator enclosures. First, the cost of an enclosure can easily equal that of the generator set. Plus, depending on the amount of attenuation required, generator operation may be impacted due to restricted ventilation.
However, given that noise ordinances and workplace safety regulations are here to stay, careful planning will allow you to make the best choices while keeping in mind the competing concerns of noise reduction, generator efficiency, and cost.
At Depco Power Systems, we’re strategic partners with our clients to maximize their mechanical assets portfolios. Contact us to learn how we can help you meet your critical equipment challenges.
