scholarly journals Indicative Assessment of Classroom Acoustics in Schools Built in Reinforced Concrete Technology on The Example of a School Building in Zabrze

2021 ◽  
Vol 1203 (2) ◽  
pp. 022007
Author(s):  
Marcelina Olechowska ◽  
Artur Nowoświat ◽  
Michał Marchacz ◽  
Karolina Kupczyńska
Keyword(s):  
Reinforced Concrete ◽  
Room Acoustics ◽  
School Building ◽  
Reverberation Time ◽  
Concrete Technology ◽  
Classroom Acoustics ◽  
Low Frequencies ◽  
Level Of Knowledge ◽  
The Republic ◽  
Acoustic Conditions

Abstract In view of room acoustics in schools, not only noise level is extremely important, but also the reverberation conditions in a given room. Such conditions affect the intelligibility of speech, which determines the acquisition level of knowledge conveyed by the teacher. The article presents problems of school classroom acoustics for a building made in reinforced concrete technology on the example of a school building in Zabrze. For the research, we selected one of schools established in 1970s as a memorial of the Millennium Jubilee of the Republic of Poland. The obtained results of the reverberation time indicate poor acoustic conditions, which, regrettably, is quite common in Polish schools. For low frequencies, the reverberation time of a classroom for teaching mathematics was over 2 seconds, and for medium frequencies it was almost 2 seconds. The article presents the acoustics of the studied classrooms without proposals of acoustic adaptation.

scholarly journals Acoustics of a School Building Made in Wooden Technology on the Example of Building from the Second Half of the 19th Century

2021 ◽  
Vol 1203 (3) ◽  
pp. 032107
Author(s):  
Artur Nowoświat ◽  
Marcelina Olechowska ◽  
Rafał Żuchowski
Keyword(s):  
19Th Century ◽  
School Building ◽  
Reverberation Time ◽  
Low Frequencies ◽  
Acoustic Insulation ◽  
The 19Th Century ◽  
Typical School ◽  
Made In

Abstract The Władysław Matlakowski School in Zakopane was established in 1877. After the war damage, during the Communist rule in Poland the school was rebuilt and renovated. As a result, the original character of the classrooms was distorted. Fiberboards used for interior finishing changed the acoustic climate of the rooms. The reverberation time of the tested rooms considerably exceeds 2 seconds for low frequencies and is below 2 seconds for medium frequencies. Thus, the reverberation conditions do not differ from typical school classrooms in Poland. The tests of reverberation conditions were supplemented by the measurements of acoustic insulation of partitions separating the chool classrooms from each other and from the corridor. The studies allow to infer that the noise possibly comes from the corridors or adjacent rooms.

scholarly journals Increment of Steel Tonnage for Reinforced Concrete School Building Considering Seismic Design

2019 ◽  
Vol 8 (3S3) ◽  
pp. 351-355
Keyword(s):  
Reinforced Concrete ◽  
Seismic Design ◽  
Soil Type ◽  
Research Work ◽  
Variable Parameter ◽  
Peninsular Malaysia ◽  
School Building ◽  
Ground Acceleration ◽  
Seismic Fault ◽  
Moderate Earthquake

A series of Indonesian earthquakes, especially from Sumatra caused vibration on buildings in Peninsular Malaysia like Kuala Lumpur and Penang Island. In East Malaysia, Sabah state has been classified as a region with active local seismic fault. A moderate earthquake with Mw6.1 was occurred in Ranau on 5th June 2015 and caused damage on buildings either the structural or non-structural members. Hence, the implementation of seismic design on new buildings is important to ensure public safety. However, such action has its own pro and contra especially when dealing with cost. Therefore, current research work presents the influence of seismic design consideration on the increment of cost for steel reinforcement. For that purpose, a four storey reinforced concrete school building was generated and used as basic model for analysis, design, and taking off. Two level of seismicity representing by the reference peak ground acceleration, αgR equal to 0.07g and 0.10g has been taken into account in the structural analysis and seismic design process. Besides, three soil type namely as soil type A, soil type C, and soil type E also has been considered as variable parameter. Based on result, total steel tonnage in beams for models considering seismic design increases around 14% to 119% higher than the model without seismic design. For columns, the increment is around 13% to 155%. Generally, total cost of steel used as for concrete reinforcement of the whole structure increases around 13% to 131% depending on the level of seismicity and soil type.

scholarly journals THE PECULIARITIES OF THE SOUND FIELD ENERGY DECAY IN A ROOM WITH THE USE OF DIFFERENT PULSED SOUND SOURCES/GARSO LAUKO ENERGIJOS SLOPIMO PATALPOJE YPATUMAI, NAUDOJANT SKIRTINGUS IMPULSINIUS GARSO ŠALTINIUS

1999 ◽  
Vol 5 (2) ◽  
pp. 135-140
Author(s):  
Vytautas Stauskis
Keyword(s):  
Noise Level ◽  
Sound Field ◽  
Maximum Energy ◽  
Reverberation Time ◽  
Frequency Range ◽  
Sound Sources ◽  
Low Frequencies ◽  
High Frequencies ◽  
The Difference ◽  
Field Decay

The paper deals with the differences between the energy created by four different pulsed sound sources, ie a sound gun, a start gun, a toy gun, and a hunting gun. A knowledge of the differences between the maximum energy and the minimum energy, or the signal-noise ratio, is necessary to correctly calculate the frequency dependence of reverberation time. It has been established by investigations that the maximum energy excited by the sound gun is within the frequency range of 250 to 2000 Hz. It decreases by about 28 dB at the low frequencies. The character of change in the energy created by the hunting gun differs from that of the sound gun. There is no change in the maximum energy within the frequency range of 63–100 Hz, whereas afterwards it increases with the increase in frequency but only to the limit of 2000 Hz. In the frequency range of 63–500 Hz, the energy excited by the hunting gun is lower by 15–30 dB than that of the sound gun. As frequency increases the difference is reduced and amounts to 5–10 dB. The maximum energy of the start gun is lower by 4–5 dB than that of the hunting gun in the frequency range of up to 1000 Hz, while afterwards the difference is insignificant. In the frequency range of 125–250 Hz, the maximum energy generated by the sound gun exceeds that generated by the hunting gun by 20 dB, that by the start gun by 25 dB, and that by the toy gun—by as much as 35 dB. The maximum energy emitted by it occupies a wide frequency range of 250 to 2000 Hz. Thus, the sound gun has an advantage over the other three sound sources from the point of view of maximum energy. Up until 500 Hz the character of change in the direct sound energy is similar for all types of sources. The maximum energy of direct sound is also created by the sound gun and it increases along with frequency, the maximum values being reached at 500 Hz and 1000 Hz. The maximum energy of the hunting gun in the frequency range of 125—500 Hz is lower by about 20 dB than that of the sound gun, while the maximum energy of the toy gun is lower by about 25 dB. The maximum of the direct sound energy generated by the hunting gun, the start gun and the toy gun is found at high frequencies, ie at 1000 Hz and 2000 Hz, while the sound gun generates the maximum energy at 500 Hz and 1000 Hz. Thus, the best results are obtained when the energy is emitted by the sound gun. When the sound field is generated by the sound gun, the difference between the maximum energy and the noise level is about 35 dB at 63 Hz, while the use of the hunting gun reduces the difference to about 20–22 dB. The start gun emits only small quantities of low frequencies and is not suitable for room's acoustical analysis at 63 Hz. At the frequency of 80 Hz, the difference between the maximum energy and the noise level makes up about 50 dB, when the sound field is generated by the sound gun, and about 27 dB, when it is generated by the hunting gun. When the start gun is used, the difference between the maximum signal and the noise level is as small as 20 dB, which is not sufficient to make a reverberation time analysis correctly. At the frequency of 100 Hz, the difference of about 55 dB between the maximum energy and the noise level is only achieved by the sound gun. The hunting gun, the start gun and the toy gun create the decrease of about 25 dB, which is not sufficient for the calculation of the reverberation time. At the frequency of 125 Hz, a sufficiently large difference in the sound field decay amounting to about 40 dB is created by the sound gun, the hunting gun and the start gun, though the character of the sound field curve decay of the latter is different from the former two. At 250 Hz, the sound gun produces a field decay difference of almost 60 dB, the hunting gun almost 50 dB, the start gun almost 40 dB, and the toy gun about 45 dB. At 500 Hz, the sound field decay is sufficient when any of the four sound sources is used. The energy difference created by the sound gun is as large as 70 dB, by the hunting gun 50 dB, by the start gun 52 dB, and by the toy gun 48 dB. Such energy differences are sufficient for the analysis of acoustic indicators. At the high frequencies of 1000 to 4000 Hz, all the four sound sources used, even the toy gun, produce a good difference of the sound field decay and in all cases it is possible to analyse the reverberation process at varied intervals of the sound level decay.

scholarly journals Cooperative principles in practice: Experiences of Serbia

2021 ◽  
Vol 3 (2) ◽  
pp. 97-110
Author(s):  
Marija Nikolić ◽  
Ivan Božić ◽  
Dragica Božić
Keyword(s):  
Theoretical Consideration ◽  
Business Practice ◽  
Agricultural Cooperatives ◽  
Current Form ◽  
Low Level ◽  
The World ◽  
Level Of Knowledge ◽  
The Republic ◽  
Different Levels ◽  
Cooperative Principles

Cooperative principles represent one of the three elements of cooperative identity. In their current form, they have existed since 1995, when they were adopted by the International Cooperative Alliance, and they represent a recommendation to cooperatives around the world on how to organize their business. Adherence to these recommendations in everyday business practice of cooperatives is extremely challenging. In fact, there is a consensus in the literature that deviation from cooperative principles is inevitable. The paper analyzes the experiences of the Republic of Serbia in the implementation of cooperative principles from time of the first cooperatives until today, with special emphasis on agricultural cooperatives. The aim of this paper is to examine the extent to which cooperative principles are respected in the business of cooperatives in Serbia, what factors led to deviations from these recommendations and what consequences this had on the success of these organizations. The paper presents a synergy of theoretical consideration of the problem and examination of experiences of agricultural cooperatives in Serbia in the implementation of cooperative principles. Conducted research indicate that during the development of cooperatives, different levels of deviations from cooperative principles in the practice of agricultural cooperatives were recorded, from very mild to extremely significant deviations that led to the suppression of true cooperative nature. Modern cooperative practice in Serbia is marked by a low level of knowledge of the elements of cooperative identity by the members and management of cooperatives, which further stipulates the posibility of their implementation in practice.

Determination of stresses and dynamic coefficients when testing railway overpasses

2021 ◽  
Vol 2 (80) ◽  
pp. 229-237
Author(s):  
M.Ya. Kvashnin ◽  
◽  
I.S. Bondar ◽  
S.S. Khasenov ◽  
G.S. Bikhozhaeva ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Dynamic Coefficients ◽  
The Republic ◽  
Concrete Girder

This paper presents some results of instrumental measurements of dynamic coefficients and fiber stresses of reinforced concrete girder spans of railway overpasses under mobile load. The results obtained can be used for further monitoring of similar structures on the main railway lines of the Republic of Kazakhstan, to identify damage in the structures of bridges.

Quantifying Non-Linearity in Early Decay Curves of Measured and Computer-Modeled Room Impulse Responses of a Highly Non-Diffuse Room Exhibiting Flutter Echo

2020 ◽  
Author(s):  
Heather L. Lai ◽  
Brian Hamilton
Keyword(s):  
Linear Regression ◽  
Computer Modeling ◽  
Impulse Response ◽  
Decay Curve ◽  
Sound Field ◽  
Energy Decay ◽  
Room Acoustics ◽  
Reverberation Time ◽  
Sound Fields ◽  
Regression Curves

Abstract This paper investigates the use of two room acoustics metrics designed to evaluate the degree to which the linearity assumptions of the energy density curves are valid. The study focuses on measured and computer-modeled energy density curves derived from the room impulse response of a space exhibiting a highly non-diffuse sound field due to flutter echo. In conjunction with acoustical remediation, room impulse response measurements were taken before and after the installation of the acoustical panels. A very dramatic decrease in the reverberation time was experienced due to the addition of the acoustical panels. The two non-linearity metrics used in this study are the non-linearity parameter and the curvature. These metrics are calculated from the energy decay curves computed per octave band, based on the definitions presented in ISO 3382-2. The non-linearity parameter quantifies the deviation of the EDC from a straight line fit used to generated T20 and T30 reverberation times. Where the reverberation times are calculated based on a linear regression of the data relating to either −5 to −25 dB for T20 or −5 to −35 dB for T30 reverberation time calculations. This deviation is quantified using the correlation coefficient between the energy decay curve and the linear regression for the specified data. In order to graphically demonstrate these non-linearity metrics, the energy decay curves are plotted along with the linear regression curves for the T20 and T30 reverberation time for both the measured data and two different room acoustics computer-modeling techniques, geometric acoustics modeling and finite-difference wave-based modeling. The intent of plotting these curves together is to demonstrate the relationship between these metrics and the energy decay curve, and to evaluate their use for quantifying degree of non-linearity in non-diffuse sound fields. Observations of these graphical representations are used to evaluate the accuracy of reverberation time estimations in non-diffuse environments, and to evaluate the use of these non-linearity parameters for comparison of different computer-modeling techniques or room configurations. Using these techniques, the non-linearity parameter based on both T20 and T30 linear regression curves and the curvature parameter were calculated over 250–4000 Hz octave bands for the measured and computer-modeled room impulse response curves at two different locations and two different room configurations. Observations of these calculated results are used to evaluate the consistency of these metrics, and the application of these metrics to quantifying the degree of non-linearity of the energy decay curve derived from a non-diffuse sound field. These calculated values are also used to evaluate the differences in the degree of diffusivity between the measured and computer-modeled room impulse response. Acoustical computer modeling is often based on geometrical acoustics using ray-tracing and image-source algorithms, however, in non-diffuse sound fields, wave based methods are often able to better model the characteristic sound wave patterns that are developed. It is of interest to study whether these improvements in the wave based computer-modeling are also reflected in the non-linearity parameter calculations. The results showed that these metrics provide an effective criteria for identifying non-linearity in the energy decay curve, however for highly non-diffuse sound fields, the resulting values were found to be very sensitive to fluctuations in the energy decay curves and therefore, contain inconsistencies due to these differences.

Sign in / Sign up

Export Citation Format

Share Document