SOFTWARE SUITE FOR ACOUSTICAL CALCULATIONS SOUNDBG

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Ecology and Environmental Protection

SOFTWARE SUITE FOR ACOUSTICAL CALCULATIONS SOUNDBG

Assoc. Prof. Nikolai Nikolov1, D.Sc.

Prof. Metodi Mazhdrakov2, D.Sc.

Dobriyan Benov3

Assoc. Prof. Georgi Trapov2

1 Institute of Building Physics, Technology and Logistics, Bulgaria 2 University of Mining and Geology “St. Ivan Rilski”, Bulgaria 3 ACMO-2006 LTD, Bulgaria

ABSTRACT

Developed is software package for acoustic calculations, named SoundBG. Described

program modules should be considered as a first step in creating a sufficiently complete

programming library for acoustic calculations, which will gradually replace the

traditional graphics, tables and approximate formulas.

Keywords: Acoustical calculations, urbanism, transport noise, software

The acoustic effects in urban environment are described with relatively complex

mathematical models received trough differential equations, which describe the

spreading of the sound waves in open and/or built-up areas. From this circumstance

come two problems. The first one is mainly theoretical and is relevant to definite group

of differential equations with set boundary conditions. The second problem is relevantto the development of the calculation device, which corresponds to the complex

mathematical dependence.

In the principal publications for acoustic issues in urban areas [for example 1]

normative documents [for example 2] the two problems are resolved through the so

called “engineering estimates”.

Engineering estimates represents a different class calculation methods for resolving

designing, managing and other tasks [3]. Engineering estimations do not require

powerful calculation tools. The calculations can be made with Scientific electronic

calculators with tables and nomograms or other graphics. We will draw attention to two

weak points of the engineering estimates. The first one is that the derived solutions areapproximate. The other one is that the engineering estimates in their essence restrain the

possibility for application of the complex mathematical models. The application of such

models requires relatively complex numeral methods, like recurrent calculations,

solving transcendent equations, finding extreme values, multiple calculations with

different input data, that cannot be realized with nomograms, tables or working

formulas. The conventional calculation means are an obstacle for the introduction of the

contemporary theoretical solutions. Therefore the estimates should be replaced faster

(radically) or slower (step-by-step) with the adequate computer programs respectively

automated systems for acoustic calculations.

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International Multidisciplinary Scientific GeoConference SGEM 2011

The widespread application of the new calculation technologies requires the

development and approbation of the respective, program module.

We will try to lay down some requirements for software suites for acoustic calculations.

In first place unreservedly is the adequacy of the algorithms in the program modules.

This allows the quick introduction of the models for spreading of sound waves in open

and/or built-up area with varied input data. Great importance has called "goodwill" of

the software - for information input, output ergonomic, anti-formal and logical errors.

Anyway, automation should not be limited to literal encoding of formulas.

As a result of the conducted theoretical and experimental studies [4] we have developed

a pack of applied programs for acoustic calculations SoundBG. The described program

modules should be examined as the first stage of the development of a library program

with enough data for acoustic calculations.

Depending on the tasks the modules can be divided in five groups.

1. The programs from group Space * calculate the noise level from the transportstreams in open areas.

2. The programs from group Street * resolve the same tasks in built-up areas.

3. The programs from group Train * calculate the noise level of train transport in

open areas.

4. The programs from group Screen * calculate the efficiency for designing noise

barriers.

5. The programs from the group Build * makes acoustic calculations of

surrounding constructions of the buildings.

Figure 1. Twenty-four-hour motion of the noise level on first class road I-9 (E-87),

Sarafovo, City of Burgas

Despite of the varied tasks, the input-output data is unified significantly. The input data

is entered in uniform shaped panels. The putput is presented in tables and/or graphics.

When solving a project task relevant documentation is generated.

Most of the programs are able to operate in three modes.

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1. Calculation at constant input data.

2. Calculation with changing of specific parameters.

3. Stochastically modeling with method „Monte Carlo“.

The group Space * includes nine modules. The most important of them are following.

The module Space BG calculates the noise level of the automobile stream according to

the Bulgarian normative documents.

The modules Space OS, Space OS 24 and Space OS MC calculate the noise level

through the formula of Osipov [1] when changing the parameters of the flow in time

(figure 1) and with stochastic modeling (figure 2).

Figure. 2. Distribution of the noise level when the indexes speed, intensity andmovement of heavy vehicles in the stream are changing

The modules Space QC and Space MC calculate the decrease of the noise from

automobile stream (source with endless duration), and the modules Space QC Lim,

Space QC Lim 3 and Space QC Lim 4 calculate the decrease of the noise from – train

transport (source with limited duration).

Figure 3. Relatively decrease of the nose level when the distance is doubled

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On figures 3 and 4 are displayed implementations of the program Space QC Lim. The

graphics show relatively decrease of the noise level when the distance is doubled (figure

3) and the decrease of the noise level when moving away from the source (figure 4)

when the distance between the separate point sources in the stream is different. In both

cases the number of the single sources is constant.

Фиг. 4. Summary decrease of the nose level when moving away from the source

The modules Street H and Street HV calculate the contribution of the reflected sound

and the decrease of the noise level when changing the place of the calculation point by

the height of the buildings or the height and the speed of the automobile stream.

The module Street Max detects the height of the calculation point on the front of the

building where the noise level is maximal (figure 5).

Figure 5. The graphic displays two peaks, that correspond to the height of the

calculation point from 4 m and 27 m

The group Train * unites 14 modules.

Модулите Train BG EQ, Train BG SU and Train Max calculate the equivalent, general

and maximal level of noise when different types of trains are passing.

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The module Train 90 Move shapes the level of noise of a moving train in relation to

immovable observer (figure 6). The program detects the direction coefficient,

characteristic of sources with limited duration.

Фиг. 6. Noise level of a moving train in relation to immovable observer

The module Train LR calculates the decrease of the noise level from source with limited

duration depending on the number of single sources and the distance between them.

The group Screen * has 14 modules.

The modules Screen 0, Screen HB and Screen M XY calculate the decrease of the noise

level of thin screen the modules Screen M, Screen K and Screen PRS 1 and thick screen

Est-screen on overhead road.

The modules Screen H Var and Screen M Uni calculate the acoustic efficiency of a thinscreen at traffic stream (figure 7) and single source (figure 8).

For the design of the screens are developed the following modules: Screen HL Var, Screen

Project and Screen Project B [5],[6].

Figure 7. Connection between the efficincy and the height of the screen at different

heights of the calculation point (noise source with endless duration)

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Figure 8. Connection between the efficincy and the height of the screen at different

heights of the calculation point (single noise source)

The group Build * is designed to find the frequency response and the index of isolation from

the noise of the surrounding structures.

Developed are modules for the following types of surrounding structures:

- single-monolayer ;

- single-double layer - with sound absorbing material or vibration-fade layer;

- single-tier - from three different materials or sandwich (figure 9);

- double-walled with an air gap (figure 10).

Figure 9. Type of construction: silicate glass with a thickness of 4 mm and air gap 1-15

mm; 2-25 mm; 3-50 mm; 4-100 mm

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Figure 10. Triple glazing with different thickness of glass

The described modules can be used to resolve many tasks.

1. Obtain results in certain input data, expected level of noise in the computational

point of view efficiency of a given size, etc.

2. Acoustic assessment of architectural and building design solutions, such as

locating buildings around highways, construction of noise protection screens, etc.

3. Preparation of noise maps.

4. Evaluation of noise pollution in the production of reports on evaluation of

environmental impact assessment.

5. Studying the impact of various factors on the noise level in research, design and

training specialists.

6. Get probabilistic assessment of the modeled process, the basis of urban planning

and administrative decisions.

REFERENCES

[1] Осипов Г.Л., Прутков Б.Г., Шишкин И.А., Карагодина И.Л.Градостроительные меры борьбы с шумом. – Москва: изд-во Стройиздат. 1975. –

215 с.

[2] Наредба № 6 от 26 юни 2006 г. За показателите за шум в околната среда,

отчитащи степента на дискомфорт през различните части на денонощието,

граничните стойности на показателите за шум в околната среда, методите за

оценка на стойностите на показателите за шум и на вредните ефекти от шума

върху здравето на населението. – София. ДВ, 58/2006.

[3] Маждраков М.Г., Николов Н. Д. Особености на инженерните изчисления. //

7ма Международна научна конференция SGEM 2007, рез. докл. – Албена. 2007. –

С. 76.

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[4] Николов Н.Д. Градоустройствена акустика. – София: Университетско

издателство „Св. Климент Охридски”, 2006. – С. 236.

[5] Николов Н.Д., Писарски А.М., Маждраков М.Г., Бенов Д.М. Проектиране на

транспортен шумозащитен екран на естакадата на бул. Брюксел, гр. София. сп.

Индекс Пътища, София, бр. 1, 2011, под печат.

[6] Nikolov N.D., Mazhdrakov M.G., Benov D.M. Design of transport noise barriers.

11th International Geoconference SGEM 2011, Albena, Bulgaria, 2011.

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SOFTWARE SUITE FOR ACOUSTICAL CALCULATIONS SOUNDBG

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