As a new functional material, foam aluminum is characteristic of sound absorption and vibration attenuation. A multiple structure is put forward which composed of foam aluminum and base blankets. The sound insulation performance is investigated. The method of sound transmission loss for normal wave incidence is developed. The influences of different thick foam aluminum on the multiple structures are analyzed by numerical method, also verified by experiments. The results show that experimental results are in good agreement with the theoretical predictions and the thickness of foam aluminum has a great impact on the multiple structure’s sound transmission loss.