Definitions and units for noise and odour
The table below provides a description of the numerous definitions and units relating to noise and odour which are used by researchers and policy-makers in reports and policy documents.| Odour nuisance (Statistics Netherlands definition) | Odour nuisance is defined as experiencing frequent or occasional nuisance from stench, in line with the questions asked in the Permanent Onderzoek Leefsituatie (Ongoing Survey of Living Conditions; CBS, 1995). Sources of odour included in the survey are road traffic, industry or business, agriculture and open fires/multi-burners. |
| Severe odour nuisance (definition of the Netherlands Organisation for Applied Scientific Research, TNO) | The definition of severe odour nuisance is based on the question from the periodic nuisance survey conducted by TNO. This examines to what extent people perceive a specific source in the residential environment to be a nuisance, based on a scale of 10 points ranging from 1 (no nuisance at all) to 10 (extreme nuisance). People giving answers in the 8 to 10 range are classified as experiencing 'severe nuisance'. |
| Noise nuisance (Statistics Netherlands definition) | Noise nuisance is defined as frequent or occasional nuisance from road traffic (cars, mopeds or motorcycles), rail traffic (trains, trams, underground trains), aircraft noise, neighbours, industry or businesses and loading/unloading noise, and children at play (CBS, 1995). |
| Severe noise nuisance (TNO definition) | Severe noise nuisance is assessed on the basis of the question in the periodical nuisance survey conducted by TNO about the extent to which people perceive a specific source in the residential environment to be a nuisance, based on a scale of 10 points ranging from 0 (no nuisance at all) to 10 (extreme nuisance). People answering 7 (partially), 8, 9 or 10 are considered to experience severe nuisance (De Jong et al., 2000). |
| Noise exposure as opposed to noise nuisance | Noise exposure is the amount of noise (often corrected for the sensitivity of the human ear). The dose can be expressed in various units (see LAeq, EQU, Ltwenty-four hours, LAeq-24hours, Lden and B65). It depends on various factors, including the nature and the source of the noise. The level of noise and the pitch always play a role in the calculations. That is not always the case for the time and duration (for example in the case of LAeq-24hours and B65 respectively). Noise nuisance is the main effect (response) that noise exposure has on people. Attempts have been made, when calculating a number of units (for example the B65), to arrive at a direct indication of the nuisance cause by the noise (from a particular source). |
| Cumulative noise exposure | "Accumulation" is the term used for the calculation of the combined noise exposure from various sources. The total noise exposure from all sources is the "cumulative noise exposure". The logarithmic scale for noise exposure means that dB(A) levels cannot simply be added up to determine the level of noise exposure. |
| EQU (environmental quality unit) | The EQU takes into account the variation in nuisance caused by noise from various sources. At the same level (in decibels), noise from rail traffic is less of a nuisance than noise from road traffic and road traffic in turn generates less nuisance than air traffic. An EQU value is established by weighting the physical levels of air traffic upwards compared to road traffic and by weighting the values for rail traffic downwards. At the same EQU level, a large group of people will feel that the nuisance generated by noise from rail, road and air traffic is the same. |
| LAeq | "Equivalent A-weighted Level". This noise unit is the average for noise levels, which in practice almost always vary over time. The value is the constant level during the given period which is equivalent in acoustic terms to the varying level. The level of noise and the variation both play a role here. The A-weighting takes into account the sensitivity of the human ear to pitch. The A has no other significance. |
| Ltwenty-four hours | Equivalent noise standard (see LAeq) used in current Dutch legislation for noise from railways, roads, factories and businesses. This unit is determined by first establishing the equivalent noise levels during the day (07.00-19.00), the evening (19.00-23.00) and at night (23.00-07.00), then raising the levels for the evening and night by 5 and 10 dB(A) respectively, and finally selecting the highest of the three values. This unit is based on the assumption that noise is more of a nuisance in the evening, and even more so at night, and that the period with the highest level indicates the amount of nuisance (Calculation and measurement regulations for road and rail traffic, and industry). |
| LAeq, 24 hours | Equivalent noise unit (see LAeq) used to assess noise abatement zones. It averages out all noise levels during a period of 24 hours. The levels in the evening and at night have the same weighting as daytime levels. This assumes that people present in natural areas in the evening (and at night) do not find noise (in particular, human noise) more of a nuisance than during the day. |
| Lden | 'Lday-evening-night'. An equivalent noise unit (see LAeq) which, like the Ltwenty-four hours, gives a higher weighting for noise in the evening and at night than for noise during the day. However, an important difference with the "Dutch" Ltwenty-four hours is that periods of twenty-four hours (weighted according to duration) are included and that the period of twenty-four hours with the highest value is not the sole basis. The Lden is set out in an EU directive for ambient noise for the appraisal of noise from road and rail traffic, aviation and industry. This directive requires member states to determine the noise situation in large urban agglomerations and close to large (busy) infrastructure facilities. |
| dB(A) | The A-weighted decibel value - dB(A) - is the most common unit of noise measurement. The A-weighting takes into account the sensitivity of the human ear to pitch. Halving or doubling the noise sources corresponds to 3 units. People experience a decrease or increase of 10 units of noise exposure as respectively a halving or doubling of the volume of the noise. A selection of values: - 40 dB(A): natural background level; maximum value for noise abatement zones; - 50 dB(A): noise in a quiet residential street; - 70 dB(A): noise of an average main road at a distance of 10 metres. http://www.rivm/nl/geluid/informatief/ |
| Kosten unit (Ke) | Unit linked to B65. Ke stands for Kosten Unit ("Kosten eenheid"). The name comes from Professor Kosten, who conducted research into nuisance from aircraft noise in the Schiphol airport area in the 1960s and 1970s. |
| B65 | Unit for noise exposure around an airport to passenger and cargo aircraft. The B65 value in Ke is not calculated in the same way as the equivalent noise exposure from rail and road traffic and industry. The main difference is that the calculation only includes maximum (peak) levels. Aircraft with peak levels lower than 65 dB(A) are not included in the calculation. This means that noise exposure in Ke cannot be converted to noise exposure in dB(A). |
