Tech Papers

[32] Combined Effect of Beads and Carpet on Structureborne Sound Radiated from an Automobile Floor

This paper discusses the effect of adding beads to a floor panel in respect to radiated sound inside a vehicle. It also describes the combined effect of using beads and a carpet to meet a predefined SPL (Sound Pressure Level) target at the driver’s ear location. It has been widely demonstrated in the literature that adding beads to a floor panel reduces vibration levels at low frequency by shifting the first few modes to a higher frequency. The gain can be significant specially to reduce the peaks at the first few modes of the unbeaded panel. In many cases, design decisions are taken based on vibration levels in conjunction with the so-called ERP (Equivalent Radiated Power) assumption that assumes a direct relation between radiated power and vibration levels. In fact, using ERP assumes that radiation efficiency is equal to 1 over the whole frequency domain. This is not the case in reality and care must be taken when designing beads to ensure that the radiated sound inside the car is not greater due to increased panel stiffness, increased radiating area and increased radiating edges provided by the beads. This papers presents a case study where beaded and unbeaded floor panel vibration, radiation efficiency and radiated sound power into an automobile interior cavity are compared. It also describes the impact of such beadings on the carpet design in order to meet SPL targets

2011 – Automotive Acoustics Conference, 1st Int. ATZ Conference, Zurich, Switzerland
Denis Blanchet (ESI Group, Germany)
Arnaud Caillet (ESI Group, Germany)

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