Sound is the sensation a person experiences when sound waves with frequencies within the audible range reach their ear. These waves travel through the ear canal to the middle ear, where the eardrum and three small bones are responsible for transmitting the signal to the cochlea. It is there that hair cells respond to movement by generating electrical impulses that, through the auditory nerve, reach the part of the brain where the sensation of sound is produced.
Named after Graham Bell, the inventor of the telephone, the unit used to evaluate the intensity of a sound is the decibel (dB).
Noise is considered an unwanted sound or an unpleasant and annoying auditory sensation that can have effects on health. It was not officially considered a polluting agent until the Environmental Congress organized by the United Nations in Stockholm in 1972. From then on, the emerging European Economic Community required member countries to make an effort to legally regulate noise pollution.
In Spain, Law 37/2003 came to homogenize the scattered regulations that existed on the subject. Its purpose is to regulate noise pollution to reduce the damage it may cause to human health, property or the environment.
effects on people
Noise can seriously threaten health, causing certain effects, all harmful and of a different nature. In fact, it is proven that, at intense exposure to noise, hearing loss can turn into deafness. Transient deafness occurs due to prolonged exposures to levels of 50 to 60 dB, or due to punctual exposures to impact noise.
These deafness are generally recoverable since they do not cause injuries. However, by increasing the exposure threshold up to 75 dB in prolonged cases or up to 110 dB in a timely manner, damage to the ear may appear, producing permanent and non-recoverable deafness that is usually accompanied by other effects, such as dizziness or stress.
People affected by noise for a long time or those who have seen their tranquility, rest or concentration affected, may develop symptoms such as chronic fatigue, tendency to insomnia, cardiovascular conditions, immune system disorders, psychological disorders (depression, mania, irritability, anxiety, migraines, nausea, neurosis or psychosis), behavior disorders and hostility, moodiness or aggressiveness.
Noise in the work environment
Since we spend a lot of time in the workplace, the exposure of workers to noise should be reduced in order to prevent and avoid significant damage to health.
Exposure to noise at work is one of the risks to which many people are exposed on a daily basis, especially in certain sectors where specific machinery is used to carry out different tasks. Sometimes it is considered that the noise to which a worker is exposed is inherent to the performance of his task and is a mistake, even if he is used to its presence.
Royal Decree 286/2006 on the protection of the health and safety of workers against the risks related to exposure to noise establishes the way to proceed to minimize the effects of noise in the work environment.
The action procedure is classified into three areas:
Action on the source of noise: redistribution and isolation of sources of noise.
Action on the transmitting medium: placement of deflector barriers between the source of noise and the receiver.
Action on the receiver or worker: use of plugs, helmets, earmuffs, etc. Health surveillance of exposed workers and regular inspections of the work environment. Reduction of exposure time. Worker training on the risk due to noise exposure.
Noise level in a research laboratory
To find out noise levels, we placed two sound level meters in a research laboratory. The sound level meter is an instrument designed to measure sound pressure levels weighted in frequency and time. Generally, it consists of a microphone, a signal processor and a result presentation device.
These instruments have frequency weighting devices, the so-called weighting filters A, B and C, which allow the passage of most frequencies, but discriminate others.
The most widely used filter is the A-weighted network, developed to simulate the response curve of the human ear at moderate sound intensity levels. The reading obtained is called the sound pressure level in dBA. That is, the sound level meter responds to sound in approximately the same way as the human ear, providing objective and reproducible measurements.
The objective of the study was to verify compliance with noise regulations to which researchers in a laboratory are exposed and to propose measures to reduce noise if necessary.
To do this, we take measurements at time intervals over 5 days. The magnitudes used in the measurement strategy in the laboratory have been the sound pressure level weighted according to curve A (in dBA) and the peak level, which is the maximum sound pressure level reached in an instant of time weighted according to the curve C (in dBC).
These measurements were carried out in a laboratory where reactions of atmospheric interest were being studied and where the use of vacuum pumps, generators, analyzers and other equipment is our daily bread and they are sources of sound waves and, therefore, of noise
Measures to avoid discomfort
We verified that in the five sampled days average values of A-weighted sound intensity level were recorded below 87 dBA and C-weighted noise peak levels below 140 dBC. Therefore, we can conclude that the researchers were not exposed daily to noise levels that exceeded the values legislated by RD 286/2006, so there is no risk to health.
However, by exceeding 55 dBA on all the days measured, discomfort is generated in the workplace. Therefore, it is advisable to take different preventive measures to combat the harmful effects of noise on the scientists who work in this laboratory, since with the data obtained it is not recommended to carry out tasks and jobs that require concentration.
The proposed measures are:
Use helmets, earmuffs and plugs in the workplace when necessary, signaling at the entrance door the mandatory use of hearing protection inside.
Redistribute the laboratory with the implementation of small acoustic barriers over the emitting sources.
Acquire equipment that generates less noise, once it has to be renewed.
They are specific measures for this case but can be extrapolated to other areas.