Study and development of an in situ acoustic absorption measurement method

Tijs, Emiel

doi:10.3990/1.9789036535212

Cited by 5 publications

(5 citation statements)

References 52 publications

(160 reference statements)

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“…This way, using only one probe, it is possible to calculate the acoustic impedance. This approach has been proved valid, and its results are highly correlated with those obtained using the classic standards [22][23][24][25].…”

Section: Acoustic Testing Of the Samplesmentioning

confidence: 90%

Vibration Damping and Acoustic Behavior of PU-Filled Non-Stochastic Aluminum Cellular Solids

Carneiro

Puga

Meireles

2021

Metals

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Aluminum-based cellular solids are promising lightweight structural materials considering their high specific strength and vibration damping, being potential candidates for future railway vehicles with enhanced riding comfort and low fuel consumption. The filling of these lattices with polymer-based (i.e., polyurethane) foams may further improve the overall vibration/noise-damping without significantly increasing their density. This study explores the dynamic (i.e., frequency response) and acoustic properties of unfilled and polyurethane-filled aluminum cellular solids to characterize their behavior and explore their benefits in terms of vibration and noise-damping. It is shown that polyurethane filling can increase the vibration damping and transmission loss, especially if the infiltration process uses flexible foams. Considering sound reflection, however, it is shown that polyurethane filled samples (0.27–0.30 at 300 Hz) tend to display lower values of sound absorption coefficient relatively to unfilled samples (0.75 at 600 Hz), is this attributed to a reduction in overall porosity, tortuosity and flow resistivity. Foam-filled samples (43–44 dB at 700–1200 Hz) were shown to be more suitable to reduce sound transmission rather than reflection than unfilled samples (21 dB at 700 Hz). It was shown that the morphology of these cellular solids might be optimized depending on the desired application: (i) unfilled aluminum cellular solids are appropriate to mitigate internal noises due to their high sound absorption coefficient; and (ii) PU filled cellular solids are appropriate to prevent exterior noises and vibration damping due to their high transmission loss in a wide range of frequencies and vibration damping.

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Section: Acoustic Testing Of the Samplesmentioning

confidence: 90%

Vibration Damping and Acoustic Behavior of PU-Filled Non-Stochastic Aluminum Cellular Solids

Carneiro

Puga

Meireles

2021

Metals

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“…The relationship between P and U allows us to calculate the reflection coefficient and thus the absorption coefficient. A software controls the measurement and allows for the determination of acoustic parameters in the frequency range between 125 Hz and 4000 Hz [37,38]. This section presents methods for finding the optimal variables to make an insulation material with rice husk via the pulping method and for measuring their physical properties as thermal, surface analysis, fire behavior, and acoustic properties.…”

Section: Sound Absorption Measurementmentioning

confidence: 99%

Assessment of Elaboration and Performance of Rice Husk-Based Thermal Insulation Material for Building Applications

Rodríguez Neira,

Cárdenas-Ramírez,

Rojas-Herrera

et al. 2024

Buildings

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Developing environmentally friendly building materials with low environmental impacts is receiving more attention nowadays to face the global challenges of climate change; building insulation materials made from agricultural waste can be used for their low environmental impact and to generate responsible supplies that utilize natural resources adequately. The study aims to assess a panel made from rice husk using the pulping method. An experimental design established the proportion of rice husk, the percentage of additive (NaOH concentration), boiling time and blending time. Taguchi’s method was applied to investigate the effect on density and thermal conductivity; the final panel with optimum conditions was morphologically analyzed using scanning electron microscopy (SEM); the thermal behavior was studied by thermogravimetric analysis (TGA); fire reaction and smoldering behavior were analyzed; and characterization in water absorption and acoustic absorption performances were established. The results show thermal conductivity values between 0.037 and 0.042 W/mK, a smoldering velocity of 3.40 mm/min, and a good acoustic absorption coefficient in octave frequency bands between 125 Hz and 4 kHz greater than 0.7. These characteristics are competitive with other insulating bio-based materials available on the market. This study employed chemicals utilized by other biomaterials for the pulping process and in flame retardants. However, it is important to investigate natural treatments or those with a diminished environmental impact.

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“…Complex rooms. For scenes CR1-4, several surfaces were initially measured with a hand-held in situ device [13], consisting of a loudspeaker in a spherical enclosure and a combined sensor unit measuring sound pressure and particle velocity [14]. This method can deliver valid results for normal incidence if applied for porous absorbers in controlled scenarios, but faces several challenges otherwise.…”

Section: Reference Scenesmentioning

confidence: 99%