Acoustic performance

When a sound wave comes in contact with a soHd stmcture, such as a wall between two spaces, some of the sound energy is transmitted from the vibrating air particles into the stmcture causing it to vibrate. The vibrating stmcture, in turn, transmits some of its vibrational energy into the air particles immediately adjacent on the opposite side, thereby radiating sound to the adjacent space. For an incomplete barrier, such as a fence or open-plan office screen, sound also diffracts over the top and around the ends of the barrier. The subject of this section is confined to complete barriers that provide complete physical separation of two adjacent spaces. Procedures for estimating the acoustical performance of partial barriers can be found in References 5 and 7. 

Table 6. Acoustical Performance of Floor/Ceiling Constructions ...

Many finishes exhibit low maintenance requirements (e.g. plasticzed metallic sheeting, epoxy coatings, continuous tiling systems, etc.). Others may be more maintenance intensive and may provide lower durability. However, selection must also consider the other operating parameters such as acoustic performance (which may mandate heavier mass or more porous-surfaced materials) or load-bearing capabilities, etc. 

A practical consequence of architecture is to permit acoustical performances to large numbers of listeners by enclosing the sound source within walls. This dramatically increases the sound energy to listeners, particularly those far from the source, relative to free field conditions. A measure of the resulting frequency dependent gain of the room can be obtained from the EDR evaluated at time 0. This frequency response can be considered to be an equalization applied by the room, and is often easily perceived. 

As resultant flexibility requirements are increased on baffles, the design complexity is increased and the acoustic performance is diminished. The collected data clearly show this relationship between design... 

Chang, R.J., Riche, B Chiotis, A., "Design and Acoustic Performance of Baffles Based on Programmed Heat-activated Foams," SAETechnical Paper 1999-01-1673, 1999. 

Laboratory Measurement of the Acoustical Performance of Body Cavity Filler Materials," SAE Standard d2846. Issued 2010-05. 

A spectacular example of a ridge and valley textile structure, 320 m in length, covers the central concourse of Denver Airport Terminal (1994) and is intended to mirror the snow-capped Rocky Mountains in the distance (Brown, 1994). This is a double-layer membrane used to improve the thermal and acoustic performance of the space (Berger, 2000, pp. 220-221). It is particularly employed to reduce the impact of aircraft engine noise on the interior. As Fig. 7.12 shows, here the distinct contrast between the bright membrane (bright, even though it is double-layer) and the duller surfaces at concourse level can clearly be seen, as discussed previously in Section 7.6.2. 

Phillips S.M., P.M. Nelson, and G. Abbott. 1995. Reducing the noise from motorways The acoustic performance of porous asphalt on the M4 at Cardiff. Paper to Acoustics 95. Volume 17 Part 4, Proceedings of the Institute of Acoustics. St. Albans, Hertfordshire Institute of Acoustics. 

Acoustical performance depends upon wall design, its thickness and weight, and ultimately cost. Frequently it is not possible to optimize one factor without seriously compromising the others. 

Characteristics of the rubber (layer of 10 mm) can be found in (Wienerberger 2012) in terms of dimensions, acoustic and mechanical properties. Different densities of the rubber are available, depending on the acoustic performance targeted. It is herein equal to 810 kg/m. ... 

Two different walls are built for each aspect ratio. The first is an ordinary wall, while the second one includes soundproofing devices (rubber layers) at the bottom and the top (Fig. 6.1). This will allow the comparative study of the influence on dynamic seismic behavior of the rubber devices, basically used only to improve the acoustic performance. 

Smaller GSA-SDS specimens (29 mm diameter) comprising 1.7 mm aerogel granules are tested for acoustic performance in the small impedance tube for frequencies from 500 to 6400 Hz. The absorption coefficients and the TL in the higher frequency range are shown in Fig. 7.10a, b. 

GSA-SDS/FWMNT composites comprising of 1.7 mm granules doped with 0.025 wt%. FMWNT were evaluated for acoustic performance. The main objective was to determine whether the addition of FMWNT enhance the absorption coefficient of the composites, similar to improving the thermal conductivity, strain recovery and hydrophobicily of composites. Table 7.5 shows the snapshot of the results obtained for absorption coefficient and TL of the GSA-SDS/FMWNT composites. The addition of FMWNT in the GSA-SDS composites shows contrasting response in the absorption coefficient in Fig. 7.11 for both the low and high frequency range. It can be observed from Fig. 7.1 la that the absorption coefficients of the GSA-SDS/FMWNT composites are below that of GSA-SDS for lower frequency. But at higher frequencies, the absorption coefficients with FMWNT are drastically better than the GSA-SDS composites. 

Acoustic Performance of Silica Aerogel Composites GSA-SDS [20/80/0.56] Size 1.7mm... 

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