GUIDELINES FOR AN URBAN NOISE ORDINANCE

Federico Miyara
Acoustics and Electroacoustics Laboratory
Universidad Nacional de Rosario
Riobamba 245 bis
2000 Rosario
Argentina

E-mail: fmiyara@unrctu.edu.ar

1. Introduction

Noise pollution in large cities is an ever-growing problem, due to several factors: the increase in demographic density, the increase in the number of per capita devices, appliances and vehicles capable of generating loud noise, the fact that society is getting used to higher noise levels, and the widespread ignorance regarding the consequences of noise as well as its remedies.

Most city regulations are quite ineffective since they start by making non-realistic goals for desired maximum noise levels without first taking action on the social, economic and technological causes of noise. It is, thus, virtually impossible to enforce those regulations without doing more harm than good. This, in turn, leads to a public perception of impunity from the laws, which is judicially undesirable.

In this paper a critical review of different aspects of noise ordinances is done, pointing out several contradictions and showing why they offer only partial solutions to the problem. Then a series of guidelines is proposed in order to prepare draft urban noise ordinances, along with their rationale. Since each city has its own characteristics which influence the way their regulations are written, no efforts were made in order to give an actual detailed ordinance draft.

2. Classifying Noise Ordinances

Noise ordinances may be classified according to several criteria:

a) According to their subject: environmental, building and entitling ordinances. Environmental ones usually deal with restrictions upon acceptable indoor and outdoor noise levels in different areas or zoning districts. Building ordinances state requisites as to the acceptable noise and vibration insulation (horizontal and vertical) between dwellings, and sometimes they also address the reverberation times of rooms intended for specific uses (i.e., classrooms). Entitling ordinances regulate the acoustical conditions of buildings, halls, shops and vehicles intended for specific commercial or public activities.

b) According to their nature: preventive, punitive and declarative ordinances. Preventive ordinances prescribe actions to be taken in order to create favorable conditions towards the reduction of environmental noise, such as education, research projects and monitoring. Punitive ones attempt to discourage noisy activities by the application of different types of punishment (fines, closures). Declarative ordinances state purposes, policies, and/or supports.

c) According to the noise descriptor used to set maximum allowable levels:

peak frequency, equivalent level, statistical parameters.

d) According to the criteria applied to loosen the acceptable maximum levels:

application of corrections (according to zones, day or night, season, type of noise), exemptions, exceptions and variances.

It should be noted that many ordinances cover more than one category for each criterion.

3. Fixed and mobile noise sources

Environmental ordinances usually consider two separate noise source categories: fixed and mobile. Fixed sources are any fittings, appliances or pieces of equipment permanently located at a definite site for their industrial, commercial or private use. Mobile sources are all kinds of vehicles.

This classification originates in the need to delimit clearly each party's responsibility in a dispute caused by noise. It is quite simple to check whether a specific fixed source is causing disturbance or not, but it is not so easy in the case of a single vehicle, because the responsibility is in this case distributed over all the vehicles circulating by a given location.

In the case of fixed noise sources, ordinances provide limits to be checked at the receiver's location (usually inside a bedroom). The owner or operator of the noise source is, thus, responsible for adjusting the noise emission (or the insulation) as required to comply with those limits. In the case of vehicles, limits are set at the source instead, depending on the vehicle's weight and power. In other words, the emission of a fixed source is only restricted by way of its effect on a neighbouring receiver, whereas a vehicle's emission should comply with specific limits depending solely on the source.

Interestingly, acceptable noise levels caused by fixed sources are often much lower than those resulting in practice from traffic, even if each of the individual vehicles which form it is within its respective limits. This contradiction arises because vehicular noise bounds are the result of a series of technological and economic compromises rather than desirable or safe community noise levels.

Besides, while the noise generated by a single transient vehicle would hardly constitute a severe nuisance, the noise coming from many simultaneous and successive vehicles certainly will.

4. Noise descriptors

There are three different kinds of noise descriptors currently in use in noise ordinances. Early ordinances (city of Cordoba, Argentina) and those inspired by them are based on the concept of measuring the noise peaks (i.e., the relative maxima of the sound levels) in a given time interval. The "frequent peak level" is the A-weighted sound level which is exceeded by 7 to 60 peaks in an hour. Similarly, the "occasional peak level" is the A-weighted sound level exceeded by 1 to 6 peaks in an hour. These descriptors have the advantage of being readily measured by means of a simple sound level meter, and they also take into account the subjective effect of individual noisy events and their rate of occurrence. However, they provide neither equivalent levels, nor other statistical parameters.

More recent ordinances (such as Buenos Aires') take advantage of integrating sound level meters, nowadays readily available, which are capable of measuring the average level over time, i.e. the equivalent sound level. This descriptor has proved to be fairly well correlated with long-time exposure effects of environmental noise (see for instance Berglund, B., Lindvall, T., 1995).

Finally, some ordinances (Los Altos, California, USA) are based (explicitly or not) on the statistical parameters Ln (i.e., the sound level which is exceeded an n% of time). While these parameters take into account the statistical spread of noise levels, they provide no details as regards to individual noisy events.

5. Zoning districts

Noise ordinances often divide urban areas into different zoning districts, each with a different noise limit. These districts are usually defined as hospital, residential, commercial and industrial areas. The drawback of this approach is that it may be difficult to find geographically homogeneous districts. The mixed nature of many, if not most urban sectors, makes urban planning from a noise standpoint very difficult. It may also be very difficult to enforce the allowable noise levels, especially at the most critical areas.

6. Distributed responsibility

A unique feature of vehicular noise is that noise responsibility is distributed amongst all the vehicles which are circulating simultaneously and successively. Let Leq0 be the equivalent level of a single vehicle passing once by a given urban location at a speed v0. Then the equivalent level corresponding to k vehicles at a mean speed v may be approximated by

Leq = Leq0 + 20 log v/v0 + 10 log k

For v0 = 50 km/h and averaging over a one-hour time, we have

Leq0 = Lmax - 35 dB

where Lmax is the dynamic noise level measured by standardized procedures (for instance, IRAM-CETIA 9C standard), i.e., at a distance of 7.5 m from the vehicle's side, at full acceleration and an initial speed of 50 m/s.

The preceding formulas show that if we wish to keep Leq under a certain limit which can be reasonably considered acceptable in a given area, then it will be necessary to reduce the individual equivalent noise level, the speed, the number of vehicles, or all three. Individual vehicle's noise emission is usually regulated by national laws on traffic control (for instance the Traffic and Road Safety Act, Argentina, 1996), and for each type of vehicle a compromise is made between the available technology and cost. Urban ordinances often echo these values (or make reference to them) in their sections devoted to mobile sources. These values are usually too high to make unrestricted circulation acceptable, let alone the fact that not even the individual limits are adequately enforced. Restrictions on the amount of vehicles circulating along a street are thus mandatory if noise is to be reduced. This can be accomplished by rerouting public transport in order to avoid excessive concentration, and by limiting private vehicle. These measures would not only contribute to noise reduction but to atmospheric pollution reduction as well. Speed should also be limited to about 30 km/h.

As an example, consider a central street (commercial zone) with a limit of 60 dBA Leq, and a maximum speed of 30 km/h. If some type of vehicle has a dynamically measured noise of 80 dBA, then the preceding formulas yield a maximum flow of 88 such vehicles in an hour. In practice, a greater value could be acceptable since not all the vehicles would be in full acceleration, so perhaps the individual noise level may be confidently reduced by as much as 10 dBA. In any event, it should be noted that other types of vehicles might be circulating along that street, such as those belonging to the public transport system. Actual vehicular flow should be updated periodically.

7. Performance halls, ballrooms, parties

Premises intended for dance, parties or concerts may cause three sorts of problems: a) an exceedingly high sound level inside, with consequences for patrons and personnel ranging from simple discomfort to auditory risk, b) acoustical leakage towards neighboring areas, due to insufficient insulation, and c) riots on leaving, caused by behavior alterations after the exposure to very loud noise, as in the case of discotheques and night clubs. The first action to be taken is to enforce rigorously the applicable labor health and safety regulations (such as No. 19,587/72 Labor Hygiene and Safety Act, Argentina), since the personnel is exposed to high noise levels during the whole working shift. More strict criteria should be adopted, however, according to the characteristics of the specific groups attending those places (including their susceptibility and vulnerability), and the type of activity considered. For instance, whereas in a discotheque patrons consider it acceptable and even desirable to have very loud music at the dance floor, at the cinema the sound level should be considerably lower in order to avoid the interference caused by loud sounds on the perception of images. At party rooms, the sound level should be kept low enough to allow comfortable speech. In the case of children parties, the sound level should be much lower, not only because of the greater vulnerability of children's auditory organs, but also because of the increased effect on the speech intelligibility, and, most importantly, as a preventive resource, discouraging from the very childhood the desirability of loud noise (and even the addiction to it). The same can be said, of course, as regards to school and kindergarten.

8. Recommended sound levels

The World Health Organization (WHO), through a careful review of a large number of reports, has published a series of recommended maximum sound levels applicable to various situations. Some of the WHO criteria are listed in Table 1 (Berglund, B and Lindvall, T, 1995). These figures should be taken into account when preparing a noise ordinance draft.

Table 1. Noise levels recommended by the World Health Organization

9. Preventative aspect

From the analysis of many national and foreign noise ordinances and regulations (see for instance those from Cordoba, Rosario, Buenos Aires and Los Altos) we can conclude that the preventative aspect, i.e., a series of measures and strategies in order to anticipate occurrences rather than cope with them, is almost completely absent.

Prevention creates the necessary conditions for society to adhere to regulations regarding any subject, in an adequate and voluntary manner.

The three mainstays for any preventative action are: education, control and rapid response to social demands, and research on better methods and procedures to deal with problematic situations.

Education works on the society, making it aware of the noise problem, its causes, its consequences, and its solutions. It helps to develop hygienic customs and attitudes regarding noise, both in an individual and social fashion (i.e., what individuals can do in order to protect themselves and to protect the acoustical environment). Finally, it stimulates people to undertake a proactive attitude to demand better living standards, both of which constitute important steps towards progress.

Control helps to locate problematic situations and to take the necessary actions in order to solve them. Environmental noise monitoring and prospects through predictive models are two valuable tools for control and assessment of different kinds of urban actions. In order to be effective, control should only be undertaken by skilled technicians supplied with high quality acoustical measurement equipment.

Research should be done at universities (or other prestigious academic centers) through general or specific agreements, and the necessary funding should be included in the municipal budget. An example is the development of models describing local problems in order to look for optimum solutions at minimal cost.

10. Transition criteria

From an ideal point of view it could be argued that the limit levels included in many current ordinances are adequate. Indeed, they are often taken or adapted (with minor changes) from international standards which in their turn are based on available scientific knowledge. However, those levels are very difficult to enforce because the difference between the current levels and the desirable ones is too large, requiring in most cases not only a major technical improvement but also a change of mind in the society.

The most effective way to achieve, in the medium term, the praiseworthy objective of reducing substantially the environmental noise, is to ask for a gradual decrease of the acceptable levels. For instance, a reduction at a rate of 1 dB each year would not be an impossible task, yet it would render after 10 years an impressive reduction of 10 dB in noise pollution.

11. Penalties

Even if one can reasonably expect that as a consequence of prevention many of the prescribed actions will be voluntarily accepted and taken on by the society, there will be others which will have to be specifically required and enforced, so it is likely that there will be offenders. The classical punishment is to fine offenders, but there is usually no mention of the destination of the fines. It should be stated clearly that those funds are to be applied to reinforce preventative action through formal and informal education, control and research. Alternative penalties such as the obligation to take courses on environmental topics, particularly related to noise, and to help in community duties such as noise monitoring, should be included.

12. Proposals for a noise ordinance

The following is a list of guidelines and suggestions which may prove helpful when working on a noise ordinance draft.

1) A new sort of noise source should be introduced, to be considered as a separate category from fixed and mobile sources: the traffic noise as a collective phenomenon. This category should be addressed according to its own characteristics. This means that it should be recognized that in this case the responsibility is distributed, hence it is not punishable. The effect of regulation should be then to achieve a better traffic and transport planning, and to adopt decreasing but affordable limits of individual noise emission for each kind of vehicle on a yearly basis.

2) A measuring procedure should be introduced in order to assess the noise emission of a vehicle while in a normal street, without the need for a special and hence difficult to find place.

3) A gradual plan of urban noise reduction to be applied over a period of several years should be explicitly adopted. The successive steps should be small enough as to be feasible.

4) The introduction of some tax reductions or subsidies in order to encourage companies to invest in noise control improvements should be seriously considered.

5) Municipal inspection, control and approval of manufacturing processes should be introduced as a legal requisite for any model of vehicle intended for public transport, and noise control techniques should be carefully scrutinized in order to insure their effectiveness and sustainability.

6) A permanent educational campaign on noise, its causes, effects and solutions, involving school and mass media (formal and informal education) should be explicitly provided for. Although the details of such a campaign might be left to the local authority, important issues such as its objectives, the allocated funds, and the office(s) or department(s) in charge of implementing it should be contained in the ordinance.

7) Since vehicles are among the main sources of urban noise, knowledge as regards to noise should be an important requirement in order to receive a driving license.

8) Three types of penalties should be considered: a) The obligation on the part of the offender to take a short course on urban noise. If the offence is repeated, an active participation as a member of the task force in charge of the dissemination of noise-related information would be offered as an alternative to more severe punishment. b) Fines. It is of the utmost importance that the destination of this revenue be clearly stated. An important percentage should be devoted to fund noise-related research and preventative activities, for example to provide the enforcement office with state of the art measurement equipment. c) The obligation to deposit money in a special account until the technical problem causing the noise has been fixed. Accrued interests would have the same destination as fines.

9) Piped music at public places should be kept at a low enough level so that sensitive or hearing-impaired individuals do not feel uncomfortable. Its use as a means to mask environmental noise or to increase privacy at restaurants (by masking other people's speech) should be strongly discouraged.

10) Owners and/or managers of recreational places such as discotheques or cinemas should be required to keep the sound level of the audio at or below the accepted limit, by inserting into the signal path an electronic controller capable of adjusting automatically the system's gain. Warning messages such as "exposure to exceedingly loud sounds may cause hearing damage" should be placed in areas with sound levels near the limit. Sufficient acoustical insulation is another important requirement in order to insure minimal (and hence negligible) noise leakage towards neighboring areas or dwellings.

11) Automatic noise monitoring systems should be installed at discotheques and other places where very loud music is played. This system should contain a noise data logger which could be periodically checked in order to detect infringements. This device should be capable of detecting attempts to tamper with its operation; for instance by unplugging it or covering the microphone.

12) Enforcement officers should be highly trained technicians and should take updating courses on a periodical basis in order to get in touch with the state of the art as regards to urban noise control. Their income should be in proportion to their responsibility.

13) Environmental noise monitors should be placed in streets in order to establish a permanent record of information, useful to assess the state of noise pollution.

14) The sale of toys capable of emitting very loud sounds (see Table 1) should be forbidden because of the risk to children's hearing. Toys emitting acceptably loud sounds should anyway be sold with an accompanying label warning against loud sounds (for instance: "This toy is capable of producing loud sounds which might produce irreversible hearing damage to susceptible children"). Similar warnings with recommendations on its proper use should accompany every device, appliance, tool or audio system capable of producing dangerous sound levels.

15) Public transport in hospital areas should be kept at the minimum necessary to an adequate service, and it should be routed in a way causing the least disturbance to the most critical areas.

16) Limits should be imposed also on vibrations, since they propagate easily along large distances causing noise emission, but also because when large enough, (such as those generated by high power audio equipment or some industrial machines) could damage buildings.

17) No new airports should be allowed to operate inside urban areas, and flights from and to existing ones should be rerouted so that their effect as regards to noise be minimized as far as possible.

18) Finally, a Noise Control Committee or Office, or Department should be created in order to coordinate all the efforts towards urban noise reduction, including research, enforcement, education, consulting, etc., which would work in conjunction with other public and private organizations such as universities, other cities, etc.

Rosario, Argentina, October 1997

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