In 2008, the Chilean Ministry of the Environment (MMA) started the Noise Maps’ program for cities in Chile. In 2011, the first version of the Noise Map of Greater Santiago was completed, and during 2016, this Noise Map was updated, published and made available to the general public.

Santiago de Chile Noise Maps as of 2016

Figure 1: Daytime noise map of Chile. Source: Convergence InstrumentsFigure 1: Daytime noise map of Chile. Source: Convergence InstrumentsFigure 2: Nightime noise map of Chile. Source: Convergence InstrumentsFigure 2: Nightime noise map of Chile. Source: Convergence Instruments

What is a noise map?

A noise map is an environmental management tool that makes it possible to identify the noise levels present in a city. There are several ways to develop a noise map. The most common is by predicting noise levels, using urban variables and information on land and transport traffic. A noise map is a mathematical model and a function of transit flow and city shapes. Traffic noise is considered the main source of environmental noise in a city. Traffic can be terrestrial, aerial or maritime.

A noise map is useful because it helps to:

  • Identify places with higher or lower levels of environmental noise.
  • Diagnose and quantify populations exposed to environmental noise problems.
  • Design environmental noise control measures.
  • Evaluate the effectiveness of the environmental noise control measures.
  • Disseminate the problem of environmental noise to the public.
  • Promote public policies for the management of environmental noise.

Although noise maps are calculated based on vehicular traffic — which is also measured — it is necessary to carry out many measurements in different spots around the city. It is not enough to measure just a few minutes. It is necessary to measure for at least one continuous week, and thus collect data about both day and night, business days and weekend to measure noise behavior. These data sets are then used to verify the fitness of predictive models selected by the scientists in charge. For this project, the entity in charge of implementing and carrying out the measurements was the Acoustics Institute of the Universidad Austral de Chile.

Why and how to use NSRT128 for noise mapping?

For the Greater Santiago Noise Map, a total of eight Convergence Instruments’ NSRT128s were mounted on light poles around the city at different streets, looking at relevant vehicle flow rates, speeds and street width, among other relevant parameters. Each NSRT128 was left in place for a week to gather the data needed for the noise map modeling process. These measurements were complemented by spot measures made with hand-held sound level pressure meters from other diverse brands.

NSRT128 was right for the job because of its smart sound level meters, which are small enough for a week of unattended measurement; its highly accurate SPL data logging capabilities; and its local support and assistance through local representative Vitglobal Instrumentation Services, which supported field engineers during the measurement campaign.

Cast to the community

Finally, the map is available online for the public and as an extra layer on some mapping/gis websites, and used by authorities to plan for city pollution management.

Noise sentry has been used in some other maps, for instance, Coronel, Chile, and today is the most used noise datalogger in Chile. Universities, authorities and many consulting firms rely on Convergence Instruments’ solutions for their noise datalogging needs.