PROCEEDINGS of the 22 nd International Congress on Acoustics Noise Mapping: Paper ICA2016-401 Noise propagation software comparison: A case of study between SoundPLAN and Code_TYMPAN Esteban Zanardi (a), Jorge Carrasco Henríquez (b), Jorge Torres (c) (a) DECIBEL SUDAMERICANA S.A., Argentina, estebanzanardi@decibel.com.ar (b) DECIBEL Chile Ingeniería Acústica Ltda., Chile, jorge.carrasco@decibel.cl (c) DECIBEL Chile Ingeniería Acústica Ltda., Chile, jorge.torres@decibel.cl Abstract In this research paper a comparison between the results obtained with SoundPLAN V7.3 and Code_TYMPAN V3.9 software, both based on calculation method specified in ISO 9613 norm, is made. Taking into account the differences between commercial noise propagation software and open source software, a calculation procedure is set to accomplish a fair comparison. A case study of industrial noise is presented with two different behaviour stages and a computer model for each one is developed. The main variation is the replacement of the old silencer with a new specially designed one. Noise measurements were carried out to compare results and to give initial values of sound power level from the industrial sources in the two stages. Conclusions are made according to the measured and calculated values. Keywords: Noise Map, Code_TYMPAN, Open Source, Noise Measurement.
Noise propagation software comparison: a case of study between SoundPLAN and Code_TYMPAN 1 Introduction Noise mapping is a well extended technique to represent and predict noise propagation behaviour. Nowadays it is a requirement for European s urban agglomerations [1]and other metropolitan areas around the world [2]. Therefore, noise propagation software is of common use and numerous commercially products are available. SoundPLAN is a well-established brand with a long trajectory on the market and several professional users all over the world. On the other hand, there are just a few open source software in development. Some of them are plug-ins of bigger Geographical Information Systems (GIS) [3,4]and others are standalone software with its own graphical user interface (GUI). The software Code_TYMPAN used in this analysis belongs to the second category and was developed especially by EDF s researchers to calculate industrial noise [5,6]. Previous studies on the topic have analysed different software packages comparing speed [7,8]and accuracy [8,9]of calculation, mathematical model used[10], user-friendliness[11], functions available [11], and documentation delivered[11]. Besides, validation procedures of the open source software Code_TYMPAN have been conducted in order to reinforce the correct behaviour of the mathematical model [12,13]. Moreover, International Standard Organization (ISO) 17534 normative recently published stated validation procedures and case of analysis to ensure the quality of computational calculation[14]. Nevertheless, there are no known papers comparing commercially and non-commercially noise propagation software. Therefore, the purpose of this research paper is to implement a case analysis between the two mentioned software programs in order to compare the results and make conclusions mainly about uncertainty issues. As a prior approach and because in situ measurements were available, an industrial plant disturbing the neighbourhood was selected as our case study. 2 Procedure 2.1 Case study Our case study was an industrial plant in the city of Goya, part of the state of Corrientes, Argentina. Since the industrial plant is located in the middle of the city, there were neighbours adjacent to the back of the factory complaining about some emergency equipment. 2.2 Measurements Measurements were carried out to get a detailed description of the sound pressure equivalent levels (L eq ) emitted by the noise sources and the existing sound pressure levels in some of the neighbour houses. The instruments used were atype 1 CESVA SC 310 sound level meter and CB006 field calibrator. 2
The main sources were two C32 ACERT diesel generator of 1000 kva used for emergency occasions. Each one had a radiator output and an exhaust emitting to the measurement location. While the radiator output was connected to a dissipative silencer, the exhaust had a specially designed reactive silencer. Measurement procedure near the sound sources has been carried out following the guidelines of ISO3746 [15] (Figure 1). A survey value of the sound power level (L w ) of the noise source was obtained, which is used as an entry data in the software model. Figure 1: Measurement points close to sound sources. Table 1: Levels measured at points close to the sources (Figure 1). Point L Aeq [dba] Point L Aeq [dba] P1 88.6 P6 87.7 P2 88.2 P7 86.7 P3 85.7 S1 88.6 P4 86.9 S2 88.2 P5 86.2 S3 85.7 Final values were calculated according to the normative taking into account tonal deviation. Therefore, exhaust power level with A weighting (L W A) was 102 dba and radiator output was 104 dba. On the other hand, measurement methodology used for the neighbour dwelling was in accordance with IRAM 4062 Argentinian normative[16]. 3
Figure 2: Measurement points in the neighbour dwelling and inside industrial plant. 2.3 Calculation Settings and Test Model A computer-aided design (CAD) model was developed to import to SoundPLAN. However, it is not possible to import any type of CAD related file to the open source software, so a different model had to be developed for this analysis. Caution was taken to accomplish an identical sample and to avoid minimum differences that could influence noise propagation results. Since our test case corresponded to an analysis of an industrial plant and was not related to road or railway traffic noise, ISO 9613-2[17]was the only calculation method used. In the case of Code_TYMPAN, calculation was made with the DefaultSolverincluded. According to the manual the method is based on the ISO 9613-2 with some modifications. The most important differences are the procedure to calculate the reflections on the ground, the directivity of volumetric sources and the possibility of taking into account interferences. Atmospheric attenuation term (A atm ), which is expected to depend on the meteorological conditions was calculated in order to represent the real measurement situation depicted in Table 2. Table 2: Weather conditions[18]. Weather parameter Value Temperature 28 C Relative Humidity 94 % Static Pressure 997.8 hpa According to the recommendations in ISO 1996-2 [19], noise maps were developed using a 1 x 1 m matrix in order not to exceed 2 db variations between adjacent points. Additionally, because these noise maps were related to the aim of assessing a community noise problem, a 4
height of 1.5 m have been used. Any efficiency set up which could diminish accuracy was not selected. The color chart used was extracted from the proposal of [20] to establish a common representation. a) b) 3 Results Figure 3: Noise Models. a) Code_TYMPAN, b)soundplan Results obtained in receiver points selected are depicted in Table 3. Table 3: Comparison of dba L eq values obtained. Receiver Measured SoundPLAN ΔSP Code_TYMPAN ΔC_T E1 65.0 66.3-1.3 66.1-1.1 E2 62.3 65.6-3.3 66.5-4.2 E3 63.4 66.3-2.9 67.3-3.9 EM 64.0 65.5-1.5 65.1-1.1 I1 86.7 88.5-1.8 87.3-0.6 I2-89.1-90.7 - I3 89.1 88.0 1.1 86.8 2.3 V1 58.9 61.5-2.6 58.4 0.5 V2 58.2 61.6-3.4 57.0 1.2 VA - 62.6-58.7 - Since the estimated accuracy stated in 9613-2 is expected to be between ± 3 db [17] for this kind of geometric model, there is a correct agreement between the three situations. In addition, the extreme meteorological conditions could be a significant factor of uncertainty. Furthermore, changing the ground configuration had an important impact onthe final value, as can be seen in Table 4. As was expected, soft ground reduced resulting values in approximately 3 db. Table 4: Comparison of results obtained in Code_TYMPAN with differenttype of ground selection. Receiver Soft Ground Hard Ground Difference E1 63.2 66.1 2.9 E2 63.7 66.5 2.8 E3 64.3 67.3 3.0 EM 62.1 65.1 3.0 5
Figure 4: Code_TYMPAN noise map. Figure 5: SoundPLAN noise map. Calculation time per computer software was annotated in order to compare their behavior. The values depicted in Table 5show that SoundPLAN is 46 to 50 times faster Code_TYMPAN per calculation point. It is also important the difference between the calculation time per point regarding the noise map tracing or the punctual receivers. 6
4 Discussions Table 5: Calculation time percomputer software. Values in [m:s:ms]. Type SoundPLAN Code_TYMPAN Receiver Points 00:00:151 00:07:000 Per calculation point 00:00:015 00:00:700 Map 00:23:461 13:58:224 Per calculation point 00:00:002 00:00:099 According to the obtained values and normative references, the two propagation computer models obtained a good relation with measured values and were within the expected uncertainty range. However, caution has to be taken in selecting different ground surfaces. The calculation time was up to 50 times smaller in the case of commercial package. Therefore, it could be an important factor when considering the analysis of large areas with many emittingsources. Open source software could be used without inconvenient in smaller community noise assessment evaluations with well-defined punctual noise sources. However, modeling of large industrial plants with complex architecture or agglomerations would take too much time to be feasible. Another issue is related to the graphical user interface and the existent reference manuals. SoundPLAN has a user friendly interface and manuals in several languages whereas Code_TYMPAN is not so well documented (only written in French) and the interface is only in English or French with some bugs. One important factor is the possibility to import CAD or other types of GIS files in SoundPLAN, which is not supported on Code_TYMPAN and implies a limiting issue regarding large planning areas. 5 Conclusions In conclusion, the two simulations have shown a good level of accuracy compared one to the other and regarding the measurement situation as well. The open source software Code_TYMPAN is not optimum to calculate large areas or planning urban noise because of its time demanding algorithm, but this first analysis supports its use to small sized projects regarding punctual well known noise sources. A more detailed validation should be done with the recently developed international normative to accomplish for it correct behaviour on different kind of situations and the expected range of uncertainty. Acknowledgments The authors would like to thank Decibel Sudamericana S.A.and DECIBEL Chile Ingeniería Acústica Ltda. for their financial support. 7
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