Liquid sloshing is becoming a major source of noise in hybrid and high-end luxury cars, especially during acceleration/deceleration driving conditions. This is due to the reduction in noise from other sources, namely, engine, transmission system, road–tyre interaction and so on. Sloshing noise is highly dependent on fluid motion in the containers. Based on the fluid motion in the containers, sloshing is classified into different regimes. The present experimental study discusses the noise generation mechanisms for various sloshing regimes. It is done by emulating different sloshing regimes in a partially filled rectangular tank by imposing longitudinal periodic excitation. The effect of fill level on noise generation phenomenon in each regime is analysed, individually, using dynamic response parameters and high-speed camera images. In this study, the measured dynamic response parameters are pressure, force, acceleration and sound pressure levels as a function of time. The fundamental reasons for the cause of sloshing noise in partially filled rectangular tanks are identified in terms of fluid motion and its interaction with the surrounding objects. The excitations upto the sloshing resonance condition cause hydraulic jumps along the tank walls leading to hit noise. Excitations beyond the sloshing natural frequency cause the predominant interaction of surface waves with surrounding fluid leading to splash noise. © IMechE 2018.