scholarly journals An Energy Model for the Calculation of Room Acoustic Parameters in Rectangular Rooms with Absorbent Ceilings

2021 ◽  
Vol 11 (14) ◽  
pp. 6607
Author(s):  
Erling Nilsson ◽  
Emma Arvidsson
Keyword(s):  
Model Comparison ◽  
Field Model ◽  
Energy Analysis ◽  
Sound Field ◽  
Acoustical Parameters ◽  
Acoustic Parameters ◽  
Reverberation Chamber ◽  
Additional Information ◽  
Classroom Configuration ◽  
Speech Clarity

The most common acoustical treatment of public rooms, such as schools, offices, and healthcare premises, is a suspended absorbent ceiling. The non-uniform distribution of the absorbent material, as well as the influence of sound-scattering objects such as furniture or other interior equipment, has to be taken into account when calculating room acoustic parameters. This requires additional information than what is already inherent in the statistical absorption coefficients and equivalent absorption areas provided by the reverberation chamber method ISO 354. Furthermore, the classical diffuse field assumption cannot be expected to be valid in these types of rooms. The non-isotropic sound field has to be considered. In this paper, a statistical energy analysis (SEA) model is derived. The sound field is subdivided into a grazing and non-grazing part where the grazing part refers to waves propagating almost parallel to the suspended ceiling. For estimation of all the inherent parameters in the model, the surface impedance of the suspended ceiling has to be known. A method for estimating the scattering and absorbing effects of furniture and objects is suggested in this paper. The room acoustical parameters reverberation time , speech clarity , and sound strength were calculated with the model and compared with calculations according to the classical diffuse field model. Comparison with measurements were performed for a classroom configuration. With regard to all cases, the new model agrees better with measurements than the classical one.

scholarly journals Pengaruh dari Direct Field Component pada Ruang Akustik dengan menggunakan SEA Model

2019 ◽  
Vol 5 (2) ◽  
Author(s):  
Al Munawir ◽  
Herri Darsan ◽  
Murhaban Murhaban
Keyword(s):  
Field Component ◽  
Model Comparison ◽  
Energy Analysis ◽  
Complex Structure ◽  
Sound Field ◽  
Coupling Loss ◽  
Model Assumption ◽  
Reflection Measurement ◽  
Acoustic Space ◽  
Good Agreement

Statistical Energy Analysis (SEA) is a well-known method to analyze the flow of acoustic and vibration energy in a complex structure. This study investigates the application of the corrected SEA model in a non-reverberant acoustic space where the direct  field component from the sound source dominates  the total  sound  field rather than  a diffuse field in a reverberant space which the  classical SEA model assumption is based on. A corrected SEA model is proposed where the direct field component in the energy is removed and the power injected in the subsystem considers only the remaining power after the loss at first reflection.  Measurement is conducted a box divided into two rooms separated by a partition with an opening where the condition of reverberant and non-reverberant can conveniently be controlled. In the case of a non-reverberant space where acoustic material was installed inside the wall of the experimental box, the signals are corrected by eliminating the direct field component in the measured impulse response. Using the corrected SEA model, comparison of the coupling loss factor (CLF) with the theory shows good agreement.

scholarly journals An Experimental Study of the Performance of a Crossed Rib Diffuser in Room Acoustic Control

2021 ◽  
Vol 11 (9) ◽  
pp. 3781
Author(s):  
Takumi Yoshida ◽  
Yasutaka Ueda ◽  
Norimasa Mori ◽  
Yumi Matano
Keyword(s):  
Sound Field ◽  
Wide Band ◽  
Scattering Coefficient ◽  
Scaled Model ◽  
One Dimensional ◽  
Broadband Absorption ◽  
Acoustic Control ◽  
Absorbing Layer ◽  
Speech Clarity ◽  
Reverberation Parameters

This paper presents a crossed rib diffuser (CRD) as an effective tool for room acoustic control. We performed an experimental investigation of its effectiveness using a specimen manufactured for this trial. The CRD is constructed by overlapping two one-dimensional (1D) periodic rib diffusers with different specifications so that they are crossed at non-right angles. The CRD achieves a higher scattering coefficient than 1D periodic rib diffusers in a wide band while maintaining the simple and friendly design of 1D periodic rib diffusers applicable to various architectural spaces. Moreover, inserting an absorbing layer between upper and lower ribs of the CRD, (CRD-A) yields a high broadband absorption coefficient. We first evaluated the random-incidence scattering coefficient of CRD using a 1/5 scaled model in comparison with those of 1D periodic diffusers assessed with a numerical method. Then, absorption coefficients for the CRD and the CRD-A were measured using a reverberation room. Subsequently, an experiment on a small meeting room with a 1D periodic rib diffuser, the CRD and the CRD-A was conducted to present performance of the CRD in room acoustic control. Impulse response measurements and evaluations of reverberation parameters (T20 and EDT) and speech clarity (D50) were conducted. Additionally, we present differences in structure of reflected sounds found for the flat wall, the CRD and the CRD-A visually using a four-channel sound field microphone.

Design and Construction of a Small Reverberation Chamber Applied to Absorption and Scattering Acoustic Measurements

2014 ◽  
Vol 1077 ◽  
pp. 197-202
Author(s):  
D. Hernandez ◽  
E.J. Liu ◽  
J.H. Huang ◽  
Y.C. Liu
Keyword(s):  
High Frequency ◽  
Integration Method ◽  
Sound Field ◽  
Acoustic Measurements ◽  
Acoustic Characteristics ◽  
Reverberation Chamber ◽  
Scattering Coefficients ◽  
Reverberation Chambers ◽  
The Cost ◽  
Design And Construction

Reverberation chambers are used to create a diffuse incidence sound field, where multiple types of acoustic measurements can be performed. The chambers tend to have a large volume in order to extent the reverberation time. However, this requirement may be conditioned by the cost and the infrastructure limitations. This paper presents the design and construction of a small-scaled reverberation chamber of 3 m3 for middle-high frequency acoustic measurements. On the design, the acoustic characteristics of chamber are confirmed via finite element computer simulation. As case studies, absorption and scattering coefficients of several materials and diffusors are measured. The reverberation times needed for the measurements were obtained by the impulse response integration method. The small reverberation chamber demonstrated to be a reliable tool for middle and high frequency acoustic measurements.

The Effect of Direct Field Component on a Statistical Energy Analysis (SEA) Model

2013 ◽  
Vol 471 ◽  
pp. 279-284 ◽  
Author(s):  
Azma Putra ◽  
Al Munawir ◽  
W.M.F.W. Mohamad ◽  
J.I. Mohammad
Keyword(s):  
Field Component ◽  
Energy Analysis ◽  
Complex Structure ◽  
Sound Field ◽  
Injection Technique ◽  
Statistical Energy Analysis ◽  
Coupling Loss ◽  
Model Assumption ◽  
Power Injection ◽  
Acoustic Space

Statistical Energy Analysis (SEA) is a well-known method to analyze the flow of acoustic and vibration energy in a complex structure. The structure is divided into subsystems where the energy in each of the subsystem is assumed to be reverberant. This study investigates the application of SEA model in a 'damped' acoustic space where the direct field component from the sound source dominates the total sound field rather than a diffuse field in a reverberant space which the SEA model assumption is based on. A measurement was conducted in a scaled room divided into two acoustic spaces separated by a partition with an opening. Absorbent materials were installed on the room walls and the power injection technique was implemented to obtain the coupling loss factor (CLF) of the system. It is found that correction of the direct field component from the subsystem energy improves the prediction of the CLF of the system.

scholarly journals Archaeoacoustic Examination of Lazarica Church

Acoustics ◽  
2019 ◽  
Vol 1 (2) ◽  
pp. 423-438 ◽  
Author(s):  
Zorana Đorđević ◽  
Dragan Novković ◽  
Uroš Andrić
Keyword(s):  
Speech Intelligibility ◽  
Acoustic Analysis ◽  
Sound Field ◽  
Simulation Software ◽  
Central Dome ◽  
Acoustic Effect ◽  
Additional Information ◽  
Medieval Church ◽  
Transmission Index ◽  
Speech Transmission

The acoustic analysis provides additional information on building tradition and related indoor practice that includes sound, thus deepening our understanding of architectural heritage. In this paper, the sound field of the Orthodox medieval church Lazarica (Kruševac city, Serbia) is examined. Lazarica is a representative of Morava architectural style, developed in the final period of the Serbian medieval state, when also the chanting art thrived, proving the importance of the aural environment in Serbian churches. The church plan is a combination of a traditional inscribed cross and a triconch. After the in situ measurement of acoustic impulse response using EASERA software, we built a computer model in the acoustic simulation software EASE and calibrated it accordingly. Following the parameters (reverberation time (T30), early decay time (EDT) and speech transmission index (STI)), we examined the acoustic effect of the space occupancy, central dome and the iconostasis. In all the cases, no significant deviation between T30 and EDT parameter was observed, which indicates uniform sound energy decay. Closing the dome with a flat ceiling did not show any significant impact on T30, but it lowered speech intelligibility. The height of iconostasis showed no significant influence on the acoustics of Lazarica church.

Analysis and Control of Internal Flow Induced Noise of Rotor Oil Pump

2014 ◽  
Vol 529 ◽  
pp. 585-588
Author(s):  
Hao Cai ◽  
Jian Li ◽  
Li Ping Yu ◽  
Ya Fei Liu ◽  
Yu He Geng
Keyword(s):  
Sound Pressure ◽  
Field Model ◽  
Three Dimensional ◽  
Sound Field ◽  
Internal Flow ◽  
Flow Noise ◽  
Oil Pump ◽  
Infinite Element Method ◽  
Flow Induced Noise ◽  
And Control

The fluid noise of rotor oil pump is studied in this paper, and the turbulent and flow sound field model of rotor oil pump are built. Based on CFD software, three dimensional unsteady internal flow field numerical simulation of some type rotor oil pump is carried out. And, the velocity and pressure simulation results at different speeds are obtained. Based on acoustic finite element and infinite element method, CFD software and acoustic solver software are used to simulate the flow induced noise of rotor oil pump. And, the sound pressure level values of monitor points in the pump are obtained. This paper puts forward some methods to reduce noise, and the experiment shows these methods can reduce the flow noise effectively.

K-coronameter observations and potential field model comparison in 1976 and 1977

1984 ◽  
Vol 89 (A7) ◽  
pp. 5381 ◽  
Author(s):  
R. Bruno ◽  
L. F. Burlaga ◽  
A. J. Hundhausen
Keyword(s):  
Potential Field ◽  
Model Comparison ◽  
Field Model

scholarly journals pSNOWPACK: a forecasting tool for avalanche warning services

2011 ◽  
Vol 5 (4) ◽  
pp. 2253-2278
Author(s):  
S. Bellaire ◽  
J. B. Jamieson ◽  
C. Fierz
Keyword(s):  
Snow Cover ◽  
Model Comparison ◽  
Weather Forecasting ◽  
Meteorological Data ◽  
Single Point ◽  
Additional Information ◽  
Stability Data ◽  
Avalanche Warning ◽  
Warning Services ◽  
Model Chain

Abstract. Avalanche danger is often estimated based on snow cover stratigraphy and snow stability data. In Canada, single forecasting regions are very large (>50 000 km2) and snow cover data are often not available. To provide additional information on the snow cover and its seasonal evolution the Swiss snow cover model SNOWPACK was therefore coupled with a regional weather forecasting model GEM15. We assess the capability of this model chain (pSNOWPACK) to forecast three key factors of snow cover instability at a single point: new snow amounts, surface hoar formation and crust formation. The output of GEM15 was compared to meteorological data from Mt. Fidelity, British Columbia, Canada, for five winters between 2005 and 2010. Forecasted precipitation amounts were generally over-estimated. The forecasted data were therefore filtered and used as input for the snow cover model. Comparison between the model output and manual observations showed that after pre-processing the input data the snow depth, new snow events and amounts were well modelled. Relevant critical layers, i.e. melt-freeze crusts and surface hoar layers were reproduced. Overall, the model chain pSNOWPACK shows promising potential as a forecasting tool for avalanche warning services in Canadian data sparse areas and could thus well be applied to similarly large regions elsewhere.

scholarly journals Influence of Sound-Absorbing Material Placement on Room Acoustical Parameters

Acoustics ◽  
2019 ◽  
Vol 1 (3) ◽  
pp. 644-660 ◽  
Author(s):  
Jose Cucharero ◽  
Tuomas Hänninen ◽  
Tapio Lokki
Keyword(s):  
Speech Intelligibility ◽  
Sound Absorption ◽  
Sound Field ◽  
Acoustical Parameters ◽  
Open Plan ◽  
Absorbing Material ◽  
The Impact

The reverberation of a room is often controlled by installing sound absorption panels to the ceiling and on the walls. The reduced reverberation is particularly important in classrooms to maximize the speech intelligibility and in open-plan offices to make spaces more pleasant. In this study, the impact of the placement of the absorption material in a room was measured in a reverberation room and in a mockup classroom. The results show that absorption material is less efficient if it is mounted to the corners or on the edges between the walls and ceiling, if the sound field is more or less diffuse. If the room modes dominate the sound field, the most efficient location for the sound-absorbing material was found at one of the surfaces causing the modes. The results help acoustical consultants to place the absorption material in optimal locations and, generally, minimize the amount of material and save costs.

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