Soundproofing

Sound-absorbing material controls reverberant sound pressure levels within a cavity, enclosure or room.

Both fibrous and porous absorption material are used to create acoustic panels, which absorb sound reflections in a room, improving speech intelligibility.

[6] Porous open cell foams are highly effective noise absorbers across a broad range of medium-high frequencies.

The exact absorption profile of a porous open-cell foam will be determined by a number of factors including cell size, tortuosity, porosity, thickness, and density.

Absorption in this sense refers to reducing a resonating frequency in a cavity by installing insulation between walls, ceilings or floors.

Acoustic panels can play a role in treatment reducing reflections that make the overall sound in the source room louder, after walls, ceilings, and floors have been soundproofed.

Adding dense material to treatment helps stop sound waves from exiting a source wall, ceiling or floor.

Materials include mass-loaded vinyl, soundproof sheetrock or drywall, plywood, fibreboard, concrete or rubber.

In an outdoor environment such as highway engineering, embankments or paneling are often used to reflect sound upwards into the sky.

[11] In the US, the FAA offers sound-reducing for homes that fall within a noise contour where the average sound level is 65 dB SPL or greater.

[12] Sealing gaps and cracks around electrical wiring, water pipes and ductwork using acoustical caulk or spray foam will significantly reduce unwanted noise as a preliminary step for ceiling soundproofing.

Spray foam insulation should only be used to fill gaps and cracks or as a 1-2 inch layer before installing mineral wool.

Mass loaded vinyl, in combination with open-cell rubber or a closed-cell foam floor underlayment, will further reduce sound transmission.

When it meets with an element such as a wall, ceiling, floor or window, which acts as a sounding board, the vibration is amplified and heard in the second space.

Restaurants, schools, office businesses, and healthcare facilities use architectural acoustics to reduce noise for their customers.

[19] The automotive environment limits the thickness of materials that can be used, but combinations of dampers, barriers, and absorbers are common.

Nowadays, multiple viscoelastic damping pads are usually attached to the body in order to attenuate higher-order structural panel modes that significantly contribute to the overall noise level inside the cabin.

In particular, laser vibrometer-type tests are often conducted on the body in white structures enabling the fast acquisition of a large number of measurement points with a good spatial resolution.

However, testing a complete vehicle is mostly infeasible, requiring evaluation of every subsystem individually, hence limiting the usability of this technology in a fast and efficient way.

Several studies have revealed the potential of particle velocity sensors for characterizing structural vibrations, which accelerates the entire testing process when combined with scanning techniques.

[23] Engineering techniques have been developed to predict an effective geometry for the noise barrier design in a particular real-world situation.