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Developing a new Healdsburg Noise Ordinance

Classifying Noise Ordinances

Excerpts from: GUIDELINES FOR AN URBAN NOISE ORDINANCE Federico Miyara -- Acoustics and Electroacoustics Laboratory, Universidad Nacional de Rosario, Argentina  (Read full text: http://www.eie.fceia.unr.edu.ar/~acustica/biblio/ordinan1.htm )

Federico Miyara analyzed noise ordinances from around the world. His studies found that noise ordinances may be classified according to several criteria:

a) According to their object: environmental, building and entitling ordinances.

• Environmental ones usually deal with restrictions upon acceptable indoors and outdoors noise level at different areas or zoning districts.

• Building ordinances state requisites as to the acceptable noise and vibration insulation (horizontal and vertical) between dwellings, and sometimes also as to the reverberation times of rooms intended for specific uses (i.e., classrooms).

• Entitling ordinances regulate the acoustical conditions with which buildings, halls, shops, vehicles intended for specific commercial or public activities should comply in order to be allowed to operate.

b) According to their nature: preventative, punitive and declarative ordinances.

• Preventative ordinances prescribe actions to be taken in order to create favourable 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, 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."

"There are three different kinds of noise descriptors currently in use in noise ordinances.

noise peaks in a given time interval

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.

sound average level over time

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).

sound level which is exceeded in a percent of time

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."

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