Different sizes, capacities, and designs of generator sets produce different noise levels. ISO 8528 part 10 (Measurement of airborne noise of generator sets) does not even establish the allowable noise level for generators per se. The noise level of the generator set perceived by the human ear is subjective and is regulated by law rather than manufacturer’s standards. However, common generator noise level measurement is taken at seven (7) meters using an A-weighted scale, dB(A) in free-field. An A-weighted scale sets the frequency response of a sound level meter similar to the reaction of the human ear. Free-field means there should be no surfaces that reflect the sounds produced by the machine such as walls, buildings, trees, etc., as they could create errors in noise level measurement.

Philippine regulation on noise:

Two types of noise standards exist in the Philippines: (1) workplace and (2) environmental noise standards. Workplace noise is regulated by the Department of Labor and Employment (DOLE), while environmental noise is regulated by the Department of Environment and Natural Resources (DENR).

Workplace noise standards protect workers who may be exposed to unwanted sound. While working around noisy workplaces, like in generator facilities, workers’ exposure to a 90 dBA noise level is limited to 8 hours. We can refer further to the workplace noise standards table set by DOLE (Table 1).

Table 1. Permissible Noise Exposure (Source: DOLE 1990)

On the other hand, environmental noise standards are a bit more elaborate than workplace noise standards. Environmental noise (or ambient noise) standard aims to protect the public or communities that reside adjacent or outside an establishment or facility emitting the noise. Here the measurement of noise may also be called perimeter noise. The Philippine standard for ambient noise is categorized into 4 classes of area and the maximum allowable noise in each class is differentiated into time schedules.

Table 2 shows the allowable environmental noise by the National Pollution Control Commission (NPCC) in 1980. The DENR still enforces this table today. The table is not solely intended for generator noise but for all sources of noise.

Table 2. Environmental Quality Standards for Noise in General Areas (Source: NPCC 1980)

Some municipalities establish generator noise level standards in Table 3.

Table 3. Generator noise level standard in some municipalities.

Should noise-emitting establishments fail to comply with regulatory standards, carefully engineered noise abatement measures must be applied.