Acoustical materials in Ireland can be commonly, and especially, a material designed to absorb sound. Sound proofing/barriers and acoustic materials are used to attenuate, deaden, or control sound and noise levels from machinery and other sources for environmental amelioration and regulatory compliance. Sound barriers and acoustic materials can use either noise reduction or noise absorption. Noise reduction reduces the energy of sound waves as they pass through. Noise absorption suppresses echoes, reverberation, resonance and reflection.
Acoustic wave is a a longitudinal wave that consists of a sequence of pulses or elastic displacements of the material, whether gas, liquid, or solid, in which the wave propagates, It also can be associated with gases, consists of a sequence of compressions and rarefactions that travel through the gas, in liquids, consists of a sequence of combined elastic deformation and compression waves that travel though the liquid, and in solids, consists of a sequence of elastic compression and expansion waves that travel though the solid.
The speed of an acoustic wave in a material medium is determined by the temperature, pressure, and elastic properties of the medium. In air, acoustic waves propagate at 332 m/s (1087 ft/s) at 0°C, at sea level. In air, sound-wave speed increases approximately 0.6 m/s (2 ft/s) for each kelvin above 0°C. Acoustic waves audible to the normal human ear are termed. [From Weik '89]
Important specifications for noise reduction and noise absorption products include noise attenuation and noise reduction coefficient. Noise attenuation is the reduction in sound pressure level that an acoustic product provides. It is measured in decibels. Absorption coefficients range between 0 and 1 and are often evaluated at many frequencies in the audible range in order to create a performance curve for the material throughout the audio spectrum.
Many different types of sound proofing and acoustic materials are available. A vinyl acoustic barrier blocks airborne noise (street traffic, voices, music) from passing through a wall, ceiling, or floor. Because vinyl acoustic barriers are made of heavy, limp vinyl, they are usually built into the structure and then covered with a finished surface like sheet rock or paneling.
Sound proofing foam dampens noise by making sound waves pass through multiple foam cells and foam cell walls. A sound proof room contains soundproofing material in the walls, floors, and ceilings. Acoustic foam and acoustic ceiling tile absorb sound to minimize echo and reverberation within a room. They do not block noise from transmitting through walls and ceilings. Sound proof doors and sound proof windows are also designed to reduce the transmission of sound. Building techniques such as double wall construction and staggering wall studs can improve the soundproofing of a room. A sound proof wall can incorporate sound proofing and acoustic materials to meet desired sound transmission class values. To measure the sound absorption of sound proofing and acoustic materials, it is important to determine the frequency range of interest, for example from 100 Hz to 5000 Hz.
