Experiments and theoretical simulation were performed to study the acoustic characteristics of a planar KrCl excilamp driven by a dielectric barrier discharge (DBD) with a mixture ratio of Kr:Cl2 = 400:1 at a pressure of 20 kPa. The acoustic spectrum of the excilamp bulb was measured and resonances at 4.96, 5.36, 9.92, 10.8, and 21.6 kHz were detected. The natural frequency of the bulb walls and the acoustic frequency of the gas were calculated. The acoustic energy of the gas was determined depending on the vibration frequency of the bulb walls. Comparison of the experimental and simulation data shows that in the frequency range >10 kHz, acoustic peaks occur at natural frequencies of the gas in the excilamp bulb.