Tier 1 suppliers and car manufacturers want more than just noise-reducing solutions. Ideally, these should be low weight, be easy to work with and permit invisible installation.
Special acoustic absorbers made of a nonwoven mixture. The fibers are substantially thinner than a human strand of hair.
Anywhere there is space and it can vanish under lining. As the graphic shows, this applies to many areas of the vehicle: the door panels and trunk liners, the headliner, the A, B and C pillars as well as the wheel-arch liners (please see visualisation).
Many manufacturers still work with insulating barrier layers. These keep the sound away from the interior by reflecting it. In other words, it reverberates back into the environment. The lightweight acoustic absorbers from FPM absorb the sound and convert the sound energy into thermal energy. This reduces the noise level both inside and outside the car.
The pads can be customized based on the customer's requirements since the material thickness and the selected fibers alter the properties of the nonwoven material. The materials used are “fine-tuned” to ideally cover the specific frequency spectrum desired by car manufacturers.
In addition to the absorbing effect, one major benefit is the minimal weight of the absorbers. The more often they are used in the vehicle, the greater the impact of the lightweight design with maximum acoustic effect.
Because the acoustic absorbers can be used very effectively in high-frequency ranges, they are excellently suited for use in electric vehicles. After all, both the rolling noises of the wheels and the wind noise are significantly more noticeable in electric cars. Typical barrier layers are superior primarily in the lower-frequency range, which is more important for diesel vehicles but substantially less important for e-vehicles. As the automotive industry undergoes a gradual transition between drive types, the demands on acoustic components will change as well.
The high sound absorption of the acoustic pads is achieved by the specific ratio of fine and coarse staple fibers in the support layer, as well as the design and material of the flow layer. The interaction between these two layers is also precisely tailored. The support layer developed by Freudenberg Performance Materials is not mechanically sewn in comparison to conventional market products. This lowers weight while the volume remains the same: an important consideration in extending the range of electrically-driven vehicles since for example heat output in winter can be reduced.
The material of the flow layer which can also function as an oscillating mass offers further advantages in terms of absorption and weight. Given the special engineering, the inner nonwoven surface is increased, which improves absorption while keeping the weight low. The flow layer can be used to bond the support layer on one or both sides as needed.