We have already talked about household sources of noise in the material “Who is making noise: noise levels of household appliances”. Comfortable noise levels for the human ear are also indicated there. Here, let's focus on the noise of electrical units and equipment with internal combustion engines, which are used during repair work, in factories or construction sites.

The tool as a noise source emits sound energy, which leads to a change in the sound pressure level in the air. Random fluctuations in the air exert their influence on the eardrums in the ears. Prolonged exposure to loud noise leads to a gradual hearing loss and may "come around" in the future with health problems up to the acquisition of deafness (complete or partial). To quantify the noise from equipment, average parameters are used that take into account the structure of the noise at the source and the properties of the environment in which the noise propagates.

Sound power (LWA)

The sound power parameter LWA is a constant value that characterizes the noise level at the source. It is measured in decibels on the body of a conventional chainsaw or diesel generator for backup power supply of a private house with electricity. However, if for a first-order instrument the sound power level will fully correspond to the measured noise level, since the working unit is directly in the hands of the operator, it is advisable for the generator or compressor to measure the sound pressure level at a certain distance from the operating unit.

The sound power parameter LWA characterizes the noise level directly from the source.

Sound pressure (LPA)

The sound pressure LPA depends on the distance between the noise source and the human ear, as well as the acoustic conditions for the propagation of sound waves. In open spaces there are no walls from which sound waves would be reflected. In enclosed spaces, some of these waves are bounced off the walls, and some are absorbed by the surface materials. The sound absorption capacity is expressed by a special coefficient from 0 to 1, where 0 corresponds to total reflection and 1 to total absorption. On its basis, the so-called Constant of the premises is calculated. The indicator is calculated taking into account the dimensions and absorption capacity of surfaces, including internal partitions.

Usually, people do not work in the immediate vicinity of generator and compressor installations, so the LPA parameter will be useful for estimating the noise level at a distance. Most often measured at a distance of 7 m from the equipment in operation, less often at a distance of 1 m. The current European Union standards require that the sound power of generating sets with a power of more than 2 kW does not exceed 97 dB - at a distance of 7 m, the noise from the engine of the conditional generator will correspond to sound pressure about 72 dB.

People rarely work in the immediate vicinity of the generator. Accordingly, the LPA parameter will be useful for estimating the noise level at a certain distance.

In the immediate vicinity of the noise source, the sound pressure level drops by 6 dB for every doubling of the distance. At greater distances from the source, the LPA level depends on the reflected sound - as the distance increases, the decrease in sound pressure slows down. When sound waves propagate from several sources in the direction of one common receiving sound pressure increases. But not two or three times, since the noise level values are determined logarithmically. If there are two noise sources with the same sound power levels, the total noise level will increase by about 3 dB.

Noise Quantification Unit (dBA)

The acoustic decibel (dBa) is used as a quantitative measure of noise from tools and construction equipment, a unit of noise level that takes into account human perception of sound. The sound pressure level is determined using a sound level metre with a special A-filter, which takes into account the characteristics of the perception of noise by a human hearing aid and corrects the measured levels for low and high frequencies.

Special sound level metres are used to measure noise in the working environment.

An approximate estimate of the noise level can be obtained by "handy means" using a smartphone, tablet or laptop with pre-installed software. The main thing is that the programme can work with the device's microphone as a sound source. So, deciBel, Decibel Metre, Noise Metre, Sound Metre applications have been released for Android mobile gadgets, Decibel 10th, Decibel Metre Pro, dB Metre, Sound Level Metre, etc. have been released for "apple" devices.

An approximate estimate of the noise level is provided by mobile gadgets when using suitable software with access to the device's microphone.

Hearing protection

Prolonged use of noisy tools and equipment is expected along with hearing protection. They need to be chosen wisely, as excessive sound attenuation can make alarms difficult to perceive and create a sense of isolation. Conversely, an insufficient level of noise suppression reduces the harmful effects of noise on the human body too little.

On noisy production sites, good noise-absorbing headphones are indispensable.

Hearing protection includes:

  • disposable and reusable noise-protective liners (ear plugs);
  • noise canceling headphones;
  • soundproof helmets;
  • anti-noise devices with radio or telephone communication.

The use of personal protective equipment for hearing organs is mandatory when the noise level in the workplace is above 85 dB. Also, employees involved in noisy work should undergo periodic medical examinations by an otolaryngologist to avoid problems associated with a hearing aid. Medical visits are essential for airport airfield workers, demolition hammer operators, and heavy construction equipment like bulldozers.

When mowing grass, it is advisable to use hearing protection in conjunction with eye protection devices.

In everyday life, ear protection comes in handy when mowing grass with a lawn mower, sawing trees with a chainsaw, chasing with a perforator, and when using other noisy tools.