Analytical model for predicting transmission of vehicle horn sound using one-dimensional standing-wave model

Vehicle horns need to satisfy sound pressure level (SPL) regulations in each country. To adhere to SPL regulations, the sound transmission of a vehicle through openings in its front grille has to be controlled by adjusting the location of the horn within the vehicle. To assist with the adjustment of horn placements in the early stages of vehicle development, this study aims to clarify relationship between the horn placements and the SPL. Therefore, an analytical model based on a one-dimensional standing-wave model is proposed to simplify the complex acoustic fields within the vehicle. First, to express the spectral shift of the SPL in response to horn position, the formation of the standing waves within the vehicles were analytically formulated based on one-dimensional acoustic wave equations. The formulated phenomena were measured in sample commercial vehicles. Next, the parameters of the analytical model were determined to accurately represent the acoustic fields within the vehicles. Finally, the analytical model was validated using measurements obtained in sample commercial vehicles. The spectral shifts obtained by the analytical model agree well with those measured in the sample commercial vehicles.