IBANA is a new research project to develop a computer-based procedure for designing the sound insulation of a building against aircraft noise. Work in the 1970s led to a design guide that has been widely used in Canada to design the sound insulation of residential buildings against aircraft noise. Unfortunately it is now very much out of date. Aircraft noise has changed, construction techniques have changed and it is now possible to produce a more accurate and a more convenient computer based procedure. This paper is a status report of this ongoing new project.
In North America, both single-unit and multiple housing is frequently built using wood stud construction. The overall performance of many common wood stud constructions is limited by excess low frequency sound transmission and with these constructions indoor aircraft noise levels are dominated by low frequency sound. A study to develop improved methods for determining the sound insulation of buildings against aircraft noise has included laboratory sound insulation measurements of 41 wood stud wall constructions. The results demonstrate the relative importance of the principal parameters: mass of surface layers, details of the wood stud system, structural breaks, and cavity insulation. Optimum designs are shown to out-perform a brick wall, which is often cited as an ideal goal for exterior wall sound insulation. In some cases less material is shown to produce better sound insulation and hence a more cost effective solution. (A) For the covering abstract see ITRD E113232.
The work to be presented is part of a large series of measurements studying sound transmission through double panel walls. The wall surfaces in this work were of 16-mm gypsum board. Studs of 38-×89-mm wood or 90-mm light steel were used with spacing between stud centerlines varying from 30 to 120 cm. The spacing between screws used to attach the gypsum board was varied with the smallest separation used being 20 cm. Transmission loss was also measured for studless constructions. Transmission loss contours showed prominent dips at frequencies influenced by stud and screw spacing. Sound absorbing material added to the cavity had only a minor effect on these resonances suggesting that they are associated with panel resonances and not with the cavity between the panels. A selection of the data from this work will be presented and discussed.
A new software called IBANA-Calc is developed for calculating the effect of sound insulation against the aircraft noise. The software is more accurate and convenient than the previous approaches that emphasize on tables and single number ratings of sound insulation. The program also includes a large database of new sound transmission loss data of building facade components and the aircraft spectra. The program can also produce audible simulations of several scenarios.
Measurements were made according to the ASTM E90 procedure but with the frequency range of measurements extended from 50 to 5 kHz. The overall performance of the walls was rated using the ASTM Outdoor-Indoor Transmission Class (OITC). In general, it was found that the overall sound insulation of wood stud exterior walls is limited by poor performance at the low frequencies due to one of 2 types of low frequency resonance.
This work reports on the development of a simple model to explain the effects of adding resilient channels to a rigid double-leaf wall or floor system. The surface layers mounted on resilient channels are treated as a vibration isolator with a fundamental resonance frequency determined by the combination of the stiffness of the resilient channels and the stiffness of the air cavity along with the masses of the surface layers. The effective stiffness of various common forms of resilient channels is determined to be approximately equivalent to that of a 160-mm air cavity. The damping of constructions including resilient channels and cavities with sound-absorbing material is found to vary with cavity depth. The model does not attempt to explain high-frequency transmission through the resilient supports but does permit the optimization of the low-frequency performance of double-leaf constructions with resilient channels. It also demonstrates that the practical range of improvements is limited.
This article reports the results of a series of measurements of the sound transmission loss of exterior wood stud walls. The measurements were made using standard laboratory procedures in which the walls were built between two reverberation chambers. The outdoor–indoor transmission class is used to rate the relative effectiveness of the various constructions. The measurement results are used to illustrate the influence of key parameters of the constructions on measured sound transmission loss values and to give guidance for future designs. The overall sound insulation of these wood stud walls, to typical outdoor noises, is shown to be limited by two types of low-frequency resonances. An understanding of these low-frequency limitations can most effectively lead to superior sound insulation in similar wood stud walls.
Sound absorbing material placed in the cavity of a hollow wall reduces the transmission of sound through the wall. The influence of density of commonly used materials, such as glass fiber, has been the subject of some argument. Also, it is sometimes thought that the position of the sound absorbing material in the cavity is important. The work to be presented is part of a large series of measurements studying sound transmission through double panel walls. Several types of glass fiber and mineral wool were placed in the cavity formed between two sheets of 3-mm-thick Lexan. Densities ranged from 10 to 145 kg/m3 and airflow resistivity ranged from 5 to 50 krayl/m. For the materials studied, the influence of material type on sound transmission class (STC) was small: only one or two points. The influence on transmission loss varied with frequency. Largest effects on transmission loss (changes of about 8 dB) were seen at the frequencies around 1000 Hz. The thickness and position of the materials were varied. Highest transmission loss was obtained when the sound absorbing material covered the entire inner surface area of the specimen. The same volume of material filling the cavity width but only partially covering the inner surface area, filling the lower half for example, gave lower transmission loss values.
'%3e%3cpath fill='%23012169' d='M0 0v30h60V0z'/%3e%3cpath stroke='%23fff' stroke-width='6' d='m0 0 60 30m0-30L0 30'/%3e%3cpath stroke='%23C8102E' stroke-width='4' d='m0 0 60 30m0-30L0 30' clip-path='url(%23b)'/%3e%3cpath stroke='%23fff' stroke-width='10' d='M30 0v30M0 15h60'/%3e%3cpath stroke='%23C8102E' stroke-width='6' d='M30 0v30M0 15h60'/%3e%3c/g%3e%3c/svg%3e)