Building Partitions Research Articles

Low-Frequency Airborne Sound Transmission through Single Partitions in Buildings – Part 2

Low-Frequency Airborne Sound Transmission through Single Partitions in Buildings – Part 2

Low-Frequency Airborne Sound Transmission through Single Partitions in Buildings

The low-frequency (20–250 Hz) airborne sound transmission of single partitions is investigated. Three theoretical models are used for the prediction: an infinite plate model, a baffled plate model and a room-plate-room model. The calculation models are verified by detailed comparisons with experimental results obtained in the laboratory. A parametric study is carried out to examine the influence of the dimensions of the room and the partition. The results demonstrate the strong modal behaviour of the low-frequency sound transmission. As a result, the low-frequency sound insulation depends not only on the properties of the test wall, but also on the geometry and the dimensions of the room-wall-room system.

Low-frequency airborne sound transmission through single partitions in buildings

The low-frequency (20–250 Hz) airborne sound transmission of single partitions is investigated. Three theoretical models are used for the prediction: an infinite plate model, a baffled plate model and a room-plate-room model. The calculation models are verified by detailed comparisons with experimental results obtained in the laboratory. A parametric study is carried out to examine the influence of the dimensions of the room and the partition. The results demonstrate the strong modal behaviour of the lowfrequency sound transmission. As a result, the low-frequency sound insulation depends not only on the properties of the test wall but also on the geometry and the dimensions of the room-wall-room system. In general, the large variation of the low-frequency insulation compromises the accuracy of prediction of the sound insulation in situ.

The longwave radiative heat transfer of the building envelopes

The longwave radiative heat transfer between outside surface of the building envelopes and the thermal environment, is treated in this paper as interesting from the point of view of the studies of the influence of the atmospheric counterradiation on the heat balance of low-sloped roofs and walls. This influence may be taken into account by means of introducing a correction that would lower outside air temperature values. This paper presents the way of calculating this correction (temperature depression) as well as the factors influencing its values. The paper submits also quantitative analysis of the influence of the longwave atmospheric radiation upon the net radiative heat loss of the low-sloped roofs and walls as a function: the thermal resistance of the building partitions, the emissivity of their outside surfaces, wind speed, the sky, the outdoor and the indoor air temperature values.

Noise control measures in the new Singapore International Airport

This paper describes some of the noise control measures incorporated in the passenger terminal building at the new Singapore International Airport at Changi. As the acoustics adviser to the Changi Airport Development Division of the Public Works Department, the overall consultant of this multi-billion dollar project, the author reviews some of the special steps taken to incorporate some of the latest acoustics techniques in this airport. These include the establishment of norms for various factors such as permissible background noise levels to each of the rooms, offices, arrival and departure halls, etc. Specifications called for include optimum sound absorption and reverberations times, airborne sound insulation for internal and external building partitions and structureborne sound insulation, as well as a sophisticated sound reinforcement system. Because of the stringent requirements following some of these specifications, the factor of the skill and workmanship of the contractors involved in the erection of the partitions had to be allowed for. As a result, all suppliers and contractors were requested to send their building proposals for testing. This was done in the newly established Acoustics Laboratory of the National University of Singapore at Kent Ridge. Some of the tests carried out, based on International Standards ISO R140 and ASTM E90 on sound transmission loss and ISO R354 and ASTM C423 on sound absorption, are evaluated.

Study of the sound transmission class system for rating building partitions: Another view

In an earlier paper titled “Subjective Study of the Sound Transmission Class System for Rating Building Partitions,” D. M. Clark concluded that his results showed that the ASTM E413 method for determining a rating from measured transmission-loss data yields conservative values even when there are large dips in the TL characteristic. Clark's experimental procedure had the subjects match the annoyance produced by a degraded STC shaped sound channel by increasing the level transmitted by a pure STC contour shaped channel. By this method, instead of having a fixed reference annoyance, the reference first established in the pure STC channel is increased in proportion to frequency, bandwidth, and depth of the degradation introduced into the so-called TL channel. If instead the reference annoyance had been kept fixed and the degraded TL channel had been readjusted to match the chosen criterion value of annoyance, quite different results would have been obtained. By using speech articulation index computations, it is shown that instead of being conservative, the rating procedure can overrate TL characteristics with high-frequency octave band dips as much as five points. Instead of abandoning the 8-dB limitation completely, it is proposed that a limitation of 16 dB for the sum of any three adjacent bands be substituted.

Racking Tests of High-Rise Building Partitions

The results of a program of racking tests of wall panels can be incorporated into the analysis of high-rise structures influenced by nonstructural partitions. Stiffness and energy-absorbing characteristics were obtained from racking tests of wall panels simulating lateral interstory displacements in high-rise buildings. These characteristics were combined with structural frame periods and damping to estimate overall building periods and damping. Illustrative examples are presented. The research program was part of the structural response research program being conducted for the U.S. Energy Research and Development Administration, Nevada Operations Office by URS/John A. Blume & Associates, Engineers.

Subjective study of the sound-transmission class system for rating building partitions.

The use of single number ratings in describing the acoustic performance of various building elements is very common. Examples of this are the sound-transmission class (STC) of a wall or the impact-noise rating of a floor. In the STC rating method, a transmission-loss (TL) curve of irregular shape is compared to a standard-reference curve. The contribution of various frequency bands depends on the shape of the standard curve and the method of comparison. An experiment has been carried out to determine the relative subjective importance of the various frequency bands and how the change in subjective rating due to irregularities in a TL curve compares with the rating obtained by using the standard curve and fitting rules. Results indicate that the present STC rating system is overconservative in rating changes in a TL curve and that narrow coincidence-type dips are not very important.

Numerical modelling of low frequency air-borne sound transmission through building partitions

A simulation of the experiments performed in the sound transmission laboratory is described. The air-borne sound transmission between two parallelipipedic rooms separated by a flexible partition is treated as a coupled structural-acoustic problem. It is shown how the sound fields in the rooms, as well as, the vibration of the panel due to acoustic excitation can be described in the Finite Element Method (FEM) and in the Modal Approach (MA). The results of numerical simulations are compared with the experimental data.

Vibration of a building partition at audio frequencies

A simple device for observing the vibration of a partition has been used for determining the resonance frequencies and associated resistance coefficients of a sheet of window glass.