Noise pollution is a growing environmental problem. The consequences of environmental noise impact, both physiological and psychophysiological, affect an increasing number of people and in particular the inhabitants of large cities; but do we know exactly what noise pollution is and how it is measured?
Environmental noise pollution
According to the spanish Law 37/2003, of 17 November, on Noise, noise pollution is defined as “the presence in the environment of noise or vibrations, whatever the acoustic emitter that originates them, which implies annoyance, risk or damage to people, to the development of their activities or to goods of any nature, even when their effect is to disturb the enjoyment of sounds of natural origin, or which cause significant effects on the environment”.
Continuous exposure to high levels of noise can have adverse effects on human health. In the short term, intense noise can cause stress, disturb sleep and impair concentration and cognitive performance. It can also cause irritability, fatigue and anxiety.
In the long term, chronic exposure to environmental noise can lead to hearing problems and excessive noise has been shown to be associated with an increased risk of cardiovascular diseases such as hypertension, heart disease and stroke.
It is therefore important to measure and control noise emissions from different noise emitters, aiming to keep them within the noise emission and immission limit values.
Noise emission and immission
Acoustic emission refers to the production and release of sound or noise by a sound source. In other words, it is the generation of noise at the source.
The sources of acoustic emission can be diverse, such as car engines, industrial machinery, air conditioning systems and others.
Noise emission is measured in decibels (dB) and is used to assess the noise impact that a given source has on its surroundings.
On the other hand, noise immission refers to the reception and exposure to noise generated by an emitting source. In other words, it is the sound input at a given location and how it affects the people in that receiving environment. It is also measured in decibels and is used to assess the noise levels to which a person or community is exposed.
Activities that may cause noise and vibration
Many activities, especially those related to transport (of any kind) or industry, are sources of emissions that generate significant noise pollution and vibrations that adversely affect the environment and people’s quality of life.
For the purposes of the law, noise emitters are classified as follows
- Motor vehicles
- Road infrastructures
- Railway infrastructure
- Airport Infrastructure
- Machinery and equipment
- Civil engineering
- Industrial activities
- Commercial activities
- Sport, leisure and recreation
- Port infrastructures
Owners of all types of noise emitters are obliged to comply with the relevant noise emission and immission limits.
Noise pollution control
Noise pollution control focuses on both the reduction of noise emissions at noise sources and the protection of people from high levels of noise immission.
To achieve this, technical measures are applied such as the use of acoustic insulation, the implementation of quieter technologies, or the adoption of specific rules and regulations in certain urban areas, for which it is essential to be able to measure noise levels in the different locations.
Pollution levels and noise indicators
The annoyance produced by a sound is directly related to its sound energy, the basic indicator of which is the sound pressure level.
This indicator varies over time and in environmental studies is measured in decibels (dB) and expressed by LA.
Considering a certain period of time, the values LAmax and LAmin, which are the maximum and minimum sound pressure level value reached in the study interval, can be determined.
The sound energy perceived by an individual in a time interval produced by a constant noise is represented by the LAeq index and to be meaningful it must always be accompanied by a time base (T). This is the most important measurement parameter at the continuous noise level.
To evaluate noise levels specifically in the time periods day, evening and night, the following acoustic indices are available:
- Ld: long-term average noise level indicator related to annoyance during the day period (generally from 7 a.m. to 7 p.m.) as defined in ISO 1996-2: 1987.
- Le: the noise indicator related to annoyance during the evening period, i.e. from 19:00 to 23:00, as defined in ISO 1996-2: 1987.
- Ln: Noise indicator related to sleep disturbance during the night period, from 23:00 to 07:00, as defined in ISO 1996-2: 1987.
The noise indicator associated with the overall annoyance Lden, expressed in decibels (dB), can be obtained by the following expression:
How to measure noise pollution?
Noise monitoring is based on the collection and analysis of data relating to the level of ambient noise in a given environment.
There are several types of equipment used to measure noise:
- Sound level meters, which are devices that measure and record sound pressure over a given time interval and provide an objective measure of noise intensity.
- Calibrators: devices that produce a stable sound at a given level and frequency and are used to adjust sound level meters to the reference sound pressure level and to check that it is maintained after measurement.
There are two types of sound level meter: Class 1 and Class 2.
A Class 1 sound level meter is considered to be more accurate than a Class 2 sound level meter due to its narrower tolerance limits.
These environmental noise meters are used to conduct acoustic surveys in urban, industrial, traffic and residential areas to assess noise indices and determine whether or not they comply with regulations.
The regulation and control of noise pollution is the responsibility of local governments and authorities, which draw up noise maps and monitor compliance with the laws that regulate noise levels: in Spain, Royal Decrees 1513/2005 of 16 December and 1367/2007 of 19 October, which develop Law 37/2003 of 17 November on noise.