Abstract Dash panel is the most important path of structure-borne and air-borne interior noise for engine-driven vehicles. Reinforcements, which are added to dash panel, are mainly designed in order to suppress the structure-borne noise contribution from the dash panel. However, the effects of dash reinforcements do not seem clear in the viewpoint of air-borne noise. In this paper, the insulation performance of a dash structure with spot-welded reinforcements is studied through several STL (Sound Transmission Loss) tests and STL simulations. The results of this study could be utilized for increasing the sound insulation performance of vehicle body structure. Introduction Vehicle interior noise is consisting of structure-borne and air-borne noise, and dash panel is considered as the most dominantly contributing panel both for structure-borne and air-borne noise. Dash panel has to be designed to efficiently block these two paths [1, 2, 3, 4, 5]. Reinforcements could be added to the dash panel region with weak stiffness by applying spot-welding in order to reduce the structure-borne noise from dash panel. This region is mainly between the cowl structure and the dash lower structure with several underbody frames. In order to give higher structural damping performance to this region, vibration deadening pads, such as asphalt pads, are inserted between dash panel and reinforcements. Because of the spot-welding, the vibration deadening pad could be applied only partially, not covering all the reinforcement area. This means, empty air gap space exists between dash panel and reinforcements.In this study, the effects of the air gaps between dash panel and reinforcements are studied by test and simulation in the view point of STL performance Test Study of Dash Structure Having Flat and Large Reinforcement A dash buck for sound transmission loss (STL) measurements is prepared from a production vehicle, which has a large and nearly-flat reinforcement on dash panel in the center of dash. Between the reinforcement and dash panel, vibration deadening pads are partially inserted and for the remaining space, there is existing thin empty space. Figure 1 is showing the conceptual view of dash panel, the reinforcement, the deadening sheet, and spot-welding positions. Along the edge of the reinforcement, the air gap space has open-end to the receiver room with 1 ∼ 3mm height. Figure 1. Conceptual view of dash panel (yellow), reinforcement (cyan), and deadening sheet for the dash structure (white). Figure 2. Test facility for STL measurements of dash buck.Study on Sound Insulation Performance of Vehicle Dash Reinforcements2014-01-2085 Published 06/30/2014 Ki-Sang Chae, Seung Hwan Lim, Ji Woo Yoo, and Seok-Gil Hong Hyundai Motor Company CITATION: Chae, K., Lim, S., Yoo, J., and Hong, S., "Study on Sound Insulation Performance of Vehicle Dash Reinforcements," SAE Technical Paper 2014-01-2085, 2014, doi:10.4271/2014-01-2085. Copyright © 2014 SAE InternationalDownloaded from SAE International by University of New South Wales, Sunday, August 19, 2018STL measurements [6] were performed for the original condition, and also for the case when mastic sealant is applied along the edge of the reinforcement in order to block the noise from the air gap space (Figure 2 and Figure 3). When the sealant is applied, STL of all the dash area is improved about 1 dB (Figure 4). Figure 3. The edge of reinforcement for which sealers are added (blue line). Figure 4. STL curves of original condition and of sealer-added condition along the reinforcement's edge. Test Study of Flat Panel With Wood Block Having Air Gap Space Between Them An idealized condition was designed and realized for a flat panel in order to investigate the sound transmission phenomena of dash panel with reinforcement. A wood block is installed above the flat panel and the distance was designed to be varying. The wood block is not directly connected to the flat panel