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Fig. 4 Initiation of Reverberation time in the Autodesk Ecotect software Regarding the data set by a designer, the closest attention is paid to the model imported into the Autodesk Ecotect software, because it provides the volume of the indoor space of the hall (Fig. 3-right). On the basis of this model Autodesk Ecotect is able to visualize propagation of sound via the sound rays (or waves) and to calculate reverberation time. The analysis of these factors in acoustics is initiated using Statistical Reverberation command in Calculate tab (Fig. 4). The space for the room volume parameter is interactive, so a designer can write some alternative volume value over it. It cannot affect the model, and thus the actual volume of the designed room, but manipulation of this value provides a good estimation of the required value of the volume required to achieve optimum reverberation time. The controlled manipulation of volume value is thus useful for the conceptual phase of the work on a lecture hall design. A designer can specify with how many seats a room has, of what material they are made (hardwood, leather or cloth upholstered (Fig. 5), what is the seat occupancy in percents.

Figure 4 Initiation of Reverberation time in the Autodesk Ecotect software Regarding the data set by a designer, the closest attention is paid to the model imported into the Autodesk Ecotect software, because it provides the volume of the indoor space of the hall (Fig. 3-right). On the basis of this model Autodesk Ecotect is able to visualize propagation of sound via the sound rays (or waves) and to calculate reverberation time. The analysis of these factors in acoustics is initiated using Statistical Reverberation command in Calculate tab (Fig. 4). The space for the room volume parameter is interactive, so a designer can write some alternative volume value over it. It cannot affect the model, and thus the actual volume of the designed room, but manipulation of this value provides a good estimation of the required value of the volume required to achieve optimum reverberation time. The controlled manipulation of volume value is thus useful for the conceptual phase of the work on a lecture hall design. A designer can specify with how many seats a room has, of what material they are made (hardwood, leather or cloth upholstered (Fig. 5), what is the seat occupancy in percents.

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Fig. 1 Different views of a structure in its physical characteristics. kinds of physical analyses, one of the being the reverberation time readout (Fig. 1). Due to good compatibility of two software packages, the models for the Autodesk Revit software are used, in which a models is designed and its materials are defined. Both software packages possess their own material databases, which are very poorly supplied with certain contemporary and technologically advanced materials.
Fig. 1 Different views of a structure in its physical characteristics. kinds of physical analyses, one of the being the reverberation time readout (Fig. 1). Due to good compatibility of two software packages, the models for the Autodesk Revit software are used, in which a models is designed and its materials are defined. Both software packages possess their own material databases, which are very poorly supplied with certain contemporary and technologically advanced materials.
Such fact is the consequence of the fact that companies dealing with the production of building materials often do not provide full specifications, thus protecting their manufacturing technology and the market. The Autodesk Ecotect software is primarily intended for the architects, and in essence it is compatible with the models of structures made in other software by Autodesk (such as AutoCAD, which is most often used by architects and other engineering.).
Such fact is the consequence of the fact that companies dealing with the production of building materials often do not provide full specifications, thus protecting their manufacturing technology and the market. The Autodesk Ecotect software is primarily intended for the architects, and in essence it is compatible with the models of structures made in other software by Autodesk (such as AutoCAD, which is most often used by architects and other engineering.).
Fig. 3 Window for calculation and display of reverberation time diagram in the Autodesk Ecotect software (left) and structural model with the marked out sound source (right) These formulae are provided in order to compare them with the Sabine formula, whereby a designer adapts the model in order to obtain as close values of the three formulae as possible. One must emphasize that, according to Parkin-Humphreys, all patterns for reverberation time contain a premise that sound surfaces of a room, which is a rare occurrence in energy is evenly distributed across all practice [3]. Such assumption is often a basic reason why the time calculated at lower frequencies often does not match the actual time. It is however clear, that the given formulae are, by nature, are intended for the statistics of behavior of rooms of various volumes, of reflective or absorbent materials (nature of absorbing means. It is necessary to indicate that Mi for measuring of reverberation time of a very large by negating their form (geometry), usage materials) and usage of special acoustic lington-Sette formula is most often used hall. When measuring reverberation time one may observe considerable discrepancy in the obtained results. Such reverberation deviations in the obtained graphs cannot be avoided. The window showing the results according to three given formulae simultaneously recommends the one formula considered by the software as the most relevant in case of the observed room (Fig. 3-left). The window for calculation of reverberation time contains commands for calculation and graphic presentation in the form of reverberation time statistics diagram for the octaves: 63Hz, 125Hz, 250Hz, 500Hz, 1000Hz, 2000Hz, 4000Hz, 8000Hz, 16000Hz.
Fig. 3 Window for calculation and display of reverberation time diagram in the Autodesk Ecotect software (left) and structural model with the marked out sound source (right) These formulae are provided in order to compare them with the Sabine formula, whereby a designer adapts the model in order to obtain as close values of the three formulae as possible. One must emphasize that, according to Parkin-Humphreys, all patterns for reverberation time contain a premise that sound surfaces of a room, which is a rare occurrence in energy is evenly distributed across all practice [3]. Such assumption is often a basic reason why the time calculated at lower frequencies often does not match the actual time. It is however clear, that the given formulae are, by nature, are intended for the statistics of behavior of rooms of various volumes, of reflective or absorbent materials (nature of absorbing means. It is necessary to indicate that Mi for measuring of reverberation time of a very large by negating their form (geometry), usage materials) and usage of special acoustic lington-Sette formula is most often used hall. When measuring reverberation time one may observe considerable discrepancy in the obtained results. Such reverberation deviations in the obtained graphs cannot be avoided. The window showing the results according to three given formulae simultaneously recommends the one formula considered by the software as the most relevant in case of the observed room (Fig. 3-left). The window for calculation of reverberation time contains commands for calculation and graphic presentation in the form of reverberation time statistics diagram for the octaves: 63Hz, 125Hz, 250Hz, 500Hz, 1000Hz, 2000Hz, 4000Hz, 8000Hz, 16000Hz.
Fig.7 Interior surfaces finish materials of A amphitheatre The volume of the A amphitheatre interior space is V=853.69m’, so according to the Harrison-Knudsen graph, the optimum reverberation time is 0,78s. In the Autodesk Ecotect software, the measure of 200 planned seats is entered, which yields the unit volume result of 4,268m’ per seat. It was already mentioned that the range of these values of lecture halls should be from 2,8m? to 42m’. The materialization of the interior surfaces of the A amphitheater (Fig.7). has the following composition: CEILING - GK ceiling plasterboard, imperforated dp = 12.5mm
Fig.7 Interior surfaces finish materials of A amphitheatre The volume of the A amphitheatre interior space is V=853.69m’, so according to the Harrison-Knudsen graph, the optimum reverberation time is 0,78s. In the Autodesk Ecotect software, the measure of 200 planned seats is entered, which yields the unit volume result of 4,268m’ per seat. It was already mentioned that the range of these values of lecture halls should be from 2,8m? to 42m’. The materialization of the interior surfaces of the A amphitheater (Fig.7). has the following composition: CEILING - GK ceiling plasterboard, imperforated dp = 12.5mm
Table 1 Measured values of reverberation time TR (s) for various frequencies f (Hz) According to the results obtained by the measuring in an empty amphitheatre, it can be concluded that there is a high value of reverberation time which starts to decrease beyond the frequency of 800Hz. The measured values are shown on the graph (Fig.10) with thick dotted lines.
Table 1 Measured values of reverberation time TR (s) for various frequencies f (Hz) According to the results obtained by the measuring in an empty amphitheatre, it can be concluded that there is a high value of reverberation time which starts to decrease beyond the frequency of 800Hz. The measured values are shown on the graph (Fig.10) with thick dotted lines.
Fig. 8 Equipment used during the reverberation time measurements Measurements of reverberation time of the A amphitheatre of the faculty of Civil Engineering and Architecture of NiS was performed according to standardized methods by measuring reverberation time on site using; building acoustic analyzer B&K 4418, sound source B&K 4224, % inch microphone type B&K 4166 plus microphone preamplifier type B&K 2639 and microphone boom B&K 3923 (Fig. 8).
Fig. 8 Equipment used during the reverberation time measurements Measurements of reverberation time of the A amphitheatre of the faculty of Civil Engineering and Architecture of NiS was performed according to standardized methods by measuring reverberation time on site using; building acoustic analyzer B&K 4418, sound source B&K 4224, % inch microphone type B&K 4166 plus microphone preamplifier type B&K 2639 and microphone boom B&K 3923 (Fig. 8).
Fig. 9 Wire model A amphitheatre adapted to the Autodesk Ecotect software for physical analyses Calculated reverberation time, obtained using the Autodesk Ecotect software in case when the amphitheatre is empty is also presented on the following graph (Fig.10). The software adopted the Sabine equation as the most suitable one, whose graph of function is more prominent. In the text below are marked the values for all three graphs of function. It is evident that the closest values to the values measured on site are those obtained with the equation favored by the software — the Sabine one. On the graph is also labeled (grayed area) the reverberation time range that enters the range close to the optimal reverberation time for speech in the case of a given room.
Fig. 9 Wire model A amphitheatre adapted to the Autodesk Ecotect software for physical analyses Calculated reverberation time, obtained using the Autodesk Ecotect software in case when the amphitheatre is empty is also presented on the following graph (Fig.10). The software adopted the Sabine equation as the most suitable one, whose graph of function is more prominent. In the text below are marked the values for all three graphs of function. It is evident that the closest values to the values measured on site are those obtained with the equation favored by the software — the Sabine one. On the graph is also labeled (grayed area) the reverberation time range that enters the range close to the optimal reverberation time for speech in the case of a given room.
‘ig. 10 Comparison of the graphs obtained by measuring (dotted lines) and the graph obtained by the Autodesk Ecotect software (thick line marks the function graph obtained by the Sabine equation)
‘ig. 10 Comparison of the graphs obtained by measuring (dotted lines) and the graph obtained by the Autodesk Ecotect software (thick line marks the function graph obtained by the Sabine equation)
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