page_title: Soundproofing
section_title: Automotive Soundproofing
hierarchical_section_title: Soundproofing / Automotive Soundproofing
caption_attribution_description: English: Sound visualization of a car floor with and without damping treatment attached to the structure
context_page_description: Soundproofing is any means of reducing the sound pressure with respect to a specified sound source and receptor. There are several basic approaches to reducing sound: increasing the distance between source and receiver, using noise barriers to reflect or absorb the energy of the sound waves, using damping structures such as sound baffles, or using active antinoise sound generators.
  There are 5 elements in sound reduction. The "Absorption" aspect in soundproofing should not be confused with Sound Absorbing Panels used in acoustic treatments. "Absorption" in this sense only refers to reducing a resonating frequency in a cavity by installing insulation between walls, ceilings or floors. Acoustic Panels can play a role in a treatment only after walls or ceilings have been soundproofed, reducing the amplified reflection in the source room.
  Two distinct soundproofing problems may need to be considered when designing acoustic treatments—to improve the sound within a room, and reduce sound leakage to/from adjacent rooms or outdoors. Acoustic quieting and noise control can be used to limit unwanted noise.
context_section_description: Automotive soundproofing aims to decrease or eliminate the effects of exterior noise, primarily engine, exhaust and tire noise across a wide frequency range. When constructing a vehicle which includes soundproofing, a panel damping material is fitted which reduces the vibration of the vehicle's body panels when they are excited by one of the many high energy sound sources caused when the vehicle is in use. There are many complex noises created within vehicles which change with the driving environment and speed at which the vehicle travels. Significant noise reductions of up to 8 dB can be achieved by installing a combination of different types of materials.
  The automotive environment limits the thickness of materials that can be used, but combinations of dampers, barriers, and absorbers are common. Common materials include felt, foam, polyester, and Polypropylene blend materials. Waterproofing may be necessary based on materials used. Acoustic foam can be applied in different areas of a vehicle during manufacture to reduce cabin noise. Foams also have cost and performance advantages in installation since foam material can expand and fill cavities after application and also prevent leaks and some gases from entering the vehicle. Vehicle soundproofing can reduce wind, engine, road, and tire noise. Vehicle soundproofing can reduce sound inside a vehicle from five to 20 decibels.
  Surface damping materials are very effective at reducing structure-borne noise. Passive damping materials have been used since the early 1960s in the aerospace industry. Over the years, advances in material manufacturing and the development of more efficient analytical and experimental tools to characterize complex dynamic behaviors enabled to expand the usage of these materials to the automotive industry. 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. Traditionally, experimental techniques are used to optimize the size and location of damping treatments. 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 unfeasible, requiring to evaluate every subsystem individually, hence limiting the usability of this technology in a fast and efficient way. Alternatively, structural vibrations can also be acoustically measured using particle velocity sensors located near a vibrating structure. Several studies have revealed the potential of particle velocity sensors for characterizing structural vibrations, which remarkably accelerates the entire testing process when combined with scanning techniques.
caption: Spatially averaged particle velocity spectra (left) and broadband colormaps of a car floor without (middle) and with (right) a damping treatment.
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