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1

Study of the Acoustic Suitability of an Open Plan Office Based on STI and DL2 Simulations

Passero C. R. M., Zannin P. H. T.

Archives of Acoustics

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2012

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Vol. 37, No. 2

237-243

EN

Many business offices around the world are organized as open plan offices. Therefore, studies about the acoustic comfort of the people who work in them have become increasingly important. The focus of this work is the acoustic evaluation of an open plan office combining several architectural characteristics and levels of ambient noise. This evaluation was performed through a computational model calibrated from a real office. The rate of spatial decay of sound pressure levels per distance doubling (DL2) and the speech transmission index (STI) were simulated for the acoustic evaluation of the office, allowing for the determination of the radius of distraction (rD). These parameters were simulated for 6 situations using different floor and ceiling covering materials and inserting or withdrawing screens between workstations. In addition, STI and rD were simulated under two conditions of ambient noise. The results indicated that the DL2 and rD are adequate acoustic parameters for the acoustic evaluation and improvement of an open plan office. The DL2 was strongly influenced by the presence or absence of screens between workstations and by the ceiling covering material. The rD was more sensitive to changes in ambient noise.

2

Evaluation of transportation noise in urbanised areas. A case study

Calixto A., Pulsides C., Zannin P. H. T.

Archives of Acoustics

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2008

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Vol. 33, No. 2

185-199

EN

The paper describes a study of noise emission levels by roads inside an urban setting. For this purpose simultaneous measurements were performed: a) noise levels Leq, L10 and L90, b) vehicle flow and c) traffic composition. Vehicle flow and traffic composition have been used to estimate sound emission levels using mathematical models. Models were developed for two different situations, either as a function of a single variable (vehicle flow, VF), or as a function of two variables (VF and percentage of heavy vehicles, HV). Results of the prediction models agreed well with measured noise levels, especially for the model considering the two independent variables, VF and HV.

3

Evaluation of performance of acoustic materials - a case study in Brazilian civil construction

Zannin P. H. T., Ferreira J.

Archives of Acoustics

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2006

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Vol. 31, No. 1

113-119

EN

Urban noises are emitted simultaneously by a wide variety of sources, such as, transportation and activities encountered in large cities. Many studies show that traffic noise followed by noise produced by neighbours are the main disturbing sources. Considering that both traffic and neighbour noise upset people inside their homes, it is possible to conclude that these homes do not display good performance of one of their purposes, which is the one of providing acoustic comfort. This fact is critical in Brazilian homes, as opposed to countries such as Germany and the USA, since these countries have specific rules for acoustic properties of materials used in civil construction, and Brazil does not. The goal of the present study is to show the acoustic performance of materials routinely used in Brazilian civil construction. Measurement procedures both in situ and in the laboratory are presented to determine acoustic performance of the materials, such as: insulation coefficient for air propagation. The results have shown that the acoustic performance of Brazilian constructions, are under international standard.

4

Parameter analysis of vibratory energy flow in a hermetic compressor by statistical energy analysis

Barbosa W. A., Lenzi A., Zannin P. H. T.

Archives of Acoustics

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2003

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Vol. 28, no. 3

151-159

EN

This work deals with the problem of vibratory energy flow from the internal electrical motor-compressor assembly (kit) to the shell of a hermetic compressor. The theoretical model is based on Statistical Energy Analysis. Shell and body vibratory energies have been measured at a standard operation condition, and the coupling loss factor thus obtained agreed well with predicted values calculated from impedance data. Several parameters, such as body and shell impedance, spring and shell loss factor, and model of the spring (tension and compression) were varied and their effects upon the compressor noise analyzed. Good agreement between theoretical and experimental results was observed.

5

Evolution of noise pollution in the Botanical Garden of Curitiba, Brazil: A case study

Zannin P. H. T., Szeremetta B., Diniz F. B

Archives of Acoustics

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2003

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Vol. 28, no. 2

101-107

EN

A study has been conducted in the Botanical Garden of the city of Curitiba, Brazil, regarding to noise pollution found in this park and generated by the nearly streets. In order to do so, measurements of noise levels have been carried out in 21 points spread troughout the park, and some local visitors were interviewed. It has been found out that 47.6% out of the measurement sites has presented noise levels that have excended 65 dB(A), which is considered as the maximum noise level one can be exposed to according to the Preventive Medicine, and 95% out of the measerement points have showed levels over the local legislation, the law number 8583 from 1995, which states the noise limits allowed for the several urban zones of the city.

6

Effects of traffic composition on noise generated by typical Brazilian roads

Lenzi A., Filho J. M. A., Zannin P. H. T.

Archives of Acoustics

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2003

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Vol. 28, no. 1

19-28

EN

The effects of traffic composition on the noise generated by typical Brazilian roads are analyzed in this work Composition is defined as the percentage of heavy vehicles (trucks and buses) with respect to the overall number of vehicles. Noise measurements were made at 10 m from lane edges of three typical roads at the city of Florianópolis, SC. All sites had indentical characteristics, such us, long and horizontal straights, free of reflections from buildings and walls, traffic flowing average speed of 80 km/h, and distant from traffic lights and round abouts. Measurements were made on the same days of the week and at the same time (from 06:00 to 10:10 h). On these three roads a total of 149 measurements were made and for each of them the percentile level L10 and the equvalent level Leq were calculated. These levels were plotted against the composition of the traffic from which were obtained empirical expressions, with reasonably good correlation indexes, which can be used for predicting road traffic noise levels based on the knowledge of traffic parameters. Information obtained in this work will help authorities to foresee the response of communities to typical Brasilian road traffic noise.

7

Vibratory energy flux study in a hermetic compressor by statistical energy analysis

Barbosa W. A., Lenzi A., Zannin P. H. T.

Archives of Acoustics

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2002

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Vol. 27, no. 1

23-30

EN

This paper presents a study of the vibratory energy transmission from the block to the shell of a hermetic compressor by the statistical energy analysis. The loss factor and modal density have been obtained experimentally. The vibratory energy of the block and shell, and the sound power radiation were also measured. The coupling loss factors from the block to shell and from the shell to the reverberation chamber have been calculated from the parameters above.

8

Acoustic two-dimensional scattering from cylinders using the method of source simulation technique

Zannin P. H. T.

Archives of Acoustics

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2002

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Vol. 27, no. 2

127-146

EN

In this work the Method of Source Simulation Technique was used to calculate the scattering of a plane wave by a circular cylinder with random distribution of the surface impedance. The scattering and radiation from vibrating bodies can be expressed by a source system that is located within the envelope of the scatterer or radiator. The Method of Comparative Sources, as is shown in this work, provides an appropriate prediction of the sources strength and consequently of the sound field. The efficiency of the method was verified through the comparison between numerical results and experimental data. The calculation of the scattering was performed for the variants of the method: the single-layer method and the one-point multipole method.

9

Factors that influence the calculation of acoustic scattering by the method of source simulation

Zannin P. H. T.

Archives of Acoustics

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2000

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Vol. 25, no. 3

317-329

EN

In this work the source simulation technique was used to calculate the scattering of a plane wave by a cylinder with radial or elliptical transverse section. The basic idea of the source simulation technique is to replace the scattering (or radiating) body with a system of simple sources located within the envelope of the scatterer (or radiator). The extent to which the simulated field reproduces the original one depends on the degree of correspondence between the simulated and the given boundary conditions. Numerical simulations have shown that: 1) the shape of the auxiliary surface; 2) the number of sources, and 3) the way the sources are distributed are the most relevant parameters to ensure an accurate solution of the problem. In the case of the single-layer method, the sources should not be positioned close to the surface or to the center of the body, because the problem becomes ill-conditioned. The auxiliary surface and the acatterer should be as similar as possible in order to minimize the boundary error. With respect to the number of sources (N), there are two opposite effects: 1) if (N) is too small, the sound field is not reproduced accurately; 2) if (N) is too large, the computing time increases and the solution accuracy decreases. The method breaks down when the excitation frequency coincides with the eigenfrequenciec - a narrow range of frequencies - of the space formed by the auxiliary surface. As the auxiliary surface is frequently represented by simple surfaces (cylinder, sphere), one can easily calculate the eigenfrequencies and therefore avoid them.