monitoring of the environmental noise level in san juan, puerto rico

8/11/2019 Monitoring of the Environmental Noise Level in San Juan, Puerto Rico

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Monitoring of the Environmental Noise Level in San Juan, Puerto Rico

Jos Alicea-PouOlga Vias-CurielWanda Cruz-Vizcarrondo

Osvaldo AlomarNoise Control Area, Puerto Rico Environmental Quality BoardBox 11488, San Juan PR 00910

Address for principal author (*): Envioronmental Quality Board, Nacional Plaza Building, 431Ponce de Len Avenue, Hato Rey, Puerto Rico 00910 Phone Number: (787)-767-8181Fax: 787-756-5831 e-mail: [email protected]

SUMMARY

The aim of the study was to describe the behavior of environmental noise levels in communitiesaround the city of San Juan, Puerto Rico. Fourteen noise stations were monitored for twenty-fourhours in order to describe the levels of environmental noise. The project is in progress with anexpected number of ninety stations by the end of 2005. The locations were selected using arandom protocol of quadrants in the city map. The sound levels were obtained with the use offour Norsonic Nor-121 sound analyzers. The different statistics (Leq, L10, L90, Lmax, Lmin, ect)

were plotted and the behavior of the graph described. Our current model for the behavior of thenoise graphs includes characteristics such as the "sustained noise level zone", the "noise dropzone", the "minimum reach level" and the "sonic rise zone". The study is part of the developmentof Puerto Ricos first Noise Action Plan. The Noise Plan will include as goals, the reduction of theaverage environmental noise levels in urban areas, the reduction of the difference between thesustained levels and the minimum reached level and the increase in the duration of the minimumreach levels.

Key Words: Environmental Noise, Urban Noise, Noise Criteria

INTRODUCTION

Until now the noise pollution problem in Puerto Rico has not been sufficiently documented andthe need for local environmental noise research (Finegold 2001) is required in order to takefurther action. The Noise Control Area (NCA) of the Environmental Quality Board (EQB) is in theprocess of conducting the first citywide noise study project with the purpose of documenting thecurrent decibel levels in various exterior locations around San Juan, Puerto Rico. In this phase ofthe project, NCA will determine the status of San Juans acoustic environment (soundscape)(Bronzaft 2000) as the first step towards setting plans to combat city noise and to educate peopleabout the quality of their acoustic environment.

To facilitate the sampling and monitoring, the research plans included dividing the city up into sixsections and randomly select various locations within these sections. Stations were set up at

each of the sites and the sound levels were monitored for 24 hours. So far, we have studiedtwenty-four sites and the project is expected to continue most of next year, expanding to othercities and rural areas of the country. By the end the project, the goal is to encompass severalhundred monitoring sites in order to create an accurate representative sound pattern of the citiesstudied.

To create effective noise legislation and understand how noise behaves in the urban areas ofPuerto Rico, it is necessary to measure different sounds types and sound intensities throughoutmultiple locations in the city. Although many possible methodologies can be used to accomplish


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these types of studies, and since the study of environmental noise can be complex, our idea wasto describe in a simple way what was the behavior of sound levels over time in different locations,and to use these characteristics to define concepts of environmental acoustic quality for PuertoRico (Figure 1). In the long run, we want this data and the results to be as simple as possible forthe general public and policy makers to comprehend and use in urban planning andpolicymaking.

METHODS

The main goal of the project was to create a sound level profile for the city based on the behaviorof the levels vs. time of the sound data for 24 hours. This profile contains information gatheredfrom randomly selected locations that were monitored for a period of 24 hours using four units ofthe sound analysis system Norsonic NOR-121. The stations where selected to ensure a sampleof all possible acoustic conditions and locations representative of the entire city. For San Juan,the city was divided into six areas and to each area a grid was applied, where each squareencompassing approximately one city block. Each square was numbered and then locationswere selected randomly from the map. The sites were then visited and evaluated for the safety ofthe location and types of possible attachment setting for the exterior microphones. After each sitewas selected as a monitoring location, one Norsonic NOR-121 unit was place and programmed tostart its analysis at 7:00 am, for a total period of 24 hours. Usually, four stations were placed on

each randomly selected day, which included weekends. Locations were residential properties,parks, highways, neighborhood streets, industrial zones, and even close to shore, among otherkinds of sites. The equipment came from the distributor with an exterior case, but we also built acase with fans, to control the temperature, and various sets of attachments for electric poles,fences and walls. We also configured a vehicle to carry the system inside, with the exteriormicrophone on the roof of the SUV vehicle; giving us the flexibility of locating the stationanywhere the vehicle could be parked.

Data was extracted from the Norsonic system and stored on a computer. The analysis started byplotting the sound levels of each monitored location on a line graph of time vs. L10or Leqsoundlevels. After each site was completed, each line was included into a multilane graph from all thelocations, creating a profile of the different sound patterns in San Juan. From this data, we canidentify periods during the day where sound levels need to be reduced and areas where the

behavior on the noise line could identify locations in need of specific actions to reduce noiselevels.

With the help of four students from the Worcester Polytechnic Institute that visited us on aninternship program, we also did multiple censuses of noise sources in each site, identifying theprominent sources and its level. With this information, we will make definitive suggestionsregarding what sources of noise are the primary causes of the noise pollution at that site and howthey can be controlled by immediate or long-term strategies. We use various units of Brel &Kjr 2236 sound level meters to describe the noise levels of these sources.

RESULTS

Based on some of the first stations studied, we defined a basic 24-hour sound pattern that is

summarized by the model shown in Figure 1. The line begins at a daytime level, with a steadylevel that starts dropping at some time after sun down, reaching a minimum level and increasingto a higher sound level as the sun rises. These are some of the characteristics of theenvironmental sound level behavior of our model. This model has become a very useful tool toexplain to the general public what is expected of the study, helps with the establishment of noisereduction goals at the city level and to educate people about how different acoustically it can beduring the day and night times, and what are the main reasons for these differences.


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Figure 1. Model of the 24 hours Behavior of Environmental Sound Levels.

After twenty-three stations monitored all over San Juan, the majority of the data followed thegeneral curve of the hypothesis for the sound profile proposed (Figure 1). Other locations hadlines that were mostly flat through the whole 24 hours period; characteristics that we feel are notideal and need further studies and stronger noise control strategies.

To form a general profile for the entire area we averaged all 30 minutes L10and Leqlevels for allthe station for all 24 hour, resulting on one line that collected of the data. These profiles areshown in Figure 2.

Average Leq and L10 values for all sites

with 5th order polynomial trendlines

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pressurelevel(dB)

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Poly. (Average Leq Values)

Poly. (Average L10 Values)

Figure 2: Sound Level Profile of San Juan Displaying the 24 Monitored Sites

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evles

Time (min)

dB(A)

Sustained level

Sonic DropSonic Rise

Minimum Level Reach

Time of Minimum reach


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After fitting the averaged data with a best-fit line, it is easy to see how similar the overall soundlevels of the city are with the anticipated profile. As a general concept, through the day, soundlevels remained fairly high (over L10= 63 db(A), until late into the night (around 11:00 pm), thenlevels reach a low level under and L10 value of 58 dB (A) around 3:00 am, dropping only for a fewhours. Additional to the behavior of the L10 and Leqlines, the data reflects the average levels thatpeople can potentially be expose in exterior environments around the city, representing this line apowerful, scientific base, awareness tool against noise. This levels could be considered highsince according to the World Health Organization (WHO), most people are moderately annoyedby levels above 50dB and seriously annoyed by levels around 55dB (WHO 2000).

One of our objectives, as explained to the general public, is to decrease the high decibel levelssustained during daytime hours to a lower average level. By explaining to the communities thatby taking multiple, site specific, noise control strategies, it could lower these daytime level, theycomprehended, in a simple way, how this would benefit their community. Another goal is toachieve that the drop in sound level occurs as early in the night as possible, especially inresidential areas. By increasing the duration of the reached minimum noise levels during thenighttime, would then result in quieter communities for longer periods of time at night. Anotherobjective is to take steps toward understanding all the factors (human activities) that couldcontribute to the abrupt increases in decibel levels as the night transitions into day time hours,and how to reduce that increase. Eventually we would like to study in more details the

contribution on nature (fauna, mainly amphibian) to the background environmental sound levels.

CONCLUSION

The preliminary data that we have collected reinforces our assertion of San Juans noise problemand suggests the necessity for noise reduction measures. The most pertinent verification of theproblem is displayed in the sound level database that we compiled which summarized the generalsound profile of the city. Of the twenty-three sites that have been monitored, we found that theLeqduring daytime hours remained around 64dB (A). With appropriate funding and cooperationfrom law enforcement and other agencies, the Environmental Quality Board can begin toestablish different short term and long term goals and plans of action to improve the acousticurban environment. Definitive legislation will lead to more efficient enforcement, while additionalfunding will provide other forms of noise reduction. At the culmination of this project, a reduction

of noise will create a more enjoyable and acoustically favorable environment for the residents ofSan Juan and Puerto Rico, ensuring both peaceful living and an increase in the quality of life.

Noise pollution is a serious problem that must be dealt with because it has numerous adverseeffects on personal health and community. A vital step in creating noise legislation is to firstassess and document noise levels throughout different areas of the city. This is crucial because itexpands the researchers knowledge of the studied city. As previously discussed, there are anumber of factors, such as the type of sound, the context of the sound, the location, the peopleinvolved, and their culture, that contribute to the perception of noise and must be taken intoconsideration when proposing legislation. Once all factors of noise pollution in a given region arestudied and assessed, any noise pollution problem can be efficiently managed using new ormodified legislation that is dependent on the needs and characteristics of that city. The soundlevels recorded and studied, the opinions of citizens through surveys and the analysis of our data

base of complaints (both not discussed in this paper) would all be incorporated with all otherconcepts needed to develop an effective, but reasonably simple, noise action plan for PuertoRico. By documenting each of these components of the noise pollution problem in San Juan,ideas and suggestions regarding more efficient legislation for the city will be easier to formulatebecause the future legislation will be based upon the characteristics of San Juans noise problemand data collected on the field.


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References

A. L. Bronzaft, Acoustic Ecologist and Environmental Psychologists: Working Toward a Quieterand Healthier Soundscape.Journal of Acoustic Ecology, Vol I, number 2 (2000).

L. S. Finegold, E. G. Henning, P. D. Schomer, B. F. Berry, Proposal for monitoring worldwidenoise exposure and assessing the effectiveness of noise exposure policies and noise controltechnologies. Noise Control Eng. J. 49 (4), 2001 July-Aug.

WHO, Guidelines for Community Noise, B. Berglund, T. Lindvall, D. Schewela, and Kee-Tai Goh,World Health Organization, Geneva, Ministry of the Environment, Singapore (2000).

monitoring of the environmental noise level in san juan, puerto rico

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