Today, a vast number of businesses and industries require backup electricity, many of which are located in cities and densely populated areas. Consequently, when selecting diesel generators, it is imperative to consider statutory regulations governing noise levels. Neglecting these standards and purchasing a non-compliant generator is not only an unethical decision regarding the surrounding community but also a violation of the law, which can serve as grounds for substantial fines.
What is Noise?
Noise is generated by the vibration of an object in space, which emits pressure waves into the air. When the amplitude of these pressure waves exceeds a certain threshold, the sound can become uncomfortable, annoying, and even painful. Noise levels are defined by the Decibel (dB) unit; however, there are two distinct measurement scales:
- dB(L): Measurement is conducted on a Linear scale, which assigns equal importance to all frequencies. (For context, human ear sensitivity ranges from 1,000 to 4,000 Hz).
- dB(A): In this model, sound measurement is derived from compliance with human hearing. Therefore, the values on this scale are weighted to more accurately reflect human auditory perception.
For diesel generators, noise data is presented using the dB(A) metric. The general approach to these parameters is as follows: 80-100 dB(A) is considered a high noise level, 100-125 dB(A) is uncomfortable, and levels of 140 dB(A) and above are pain-inducing and damaging.
Noise Measurement
For measurement purposes, microphones are installed at a distance of approximately 7 meters from the diesel generator at a 45-degree angle. Sound measurements are conducted across various frequency bands sensitive to the human ear (maximum 8 bands), and their sum determines the overall noise level.
Using this method, the ambient (background) noise level is measured first while the diesel generator is turned off. Then, the unit is switched on at full load, and the measurements are repeated for each frequency band to calculate the specific noise level of the diesel generator.
Noise Reduction
The primary sources of noise emitted by diesel generators during operation include:
- Engine Block Noise: Combustion processes in the cylinders and mechanical forces cause noise across a wide frequency range.
- Radiator Fan Noise: Sound caused by turbulence from high-speed air movement.
- Alternator Noise: Sounds resulting from airflow, friction, and vibration.
- Exhaust Noise: Noise caused by explosions within the engine cylinders.
Manufacturers employ various methods to mitigate noise levels from the aforementioned sources, such as:
- Acoustic Barriers: The enclosure (canopy) is fabricated from steel panels, while electrical cables, fuel pipes, and other intake components are fitted with specialized sealing/packaging.
- Acoustic Insulation: Sound-absorbing insulation materials applied to internal panels.
- Isolation Mounts: The generator, engine, and auxiliary components are connected using anti-vibration mounts (isolators) to decouple mechanical vibration.
Cooling Air Attenuation: Baffles (sound attenuators) installed within the air circulation ducts.