The application of silencers in scenarios requiring both ventilation and sound insulation is extensive, and minimizing their size is an unremitting pursuit. This paper proposes a method to enhance the low-frequency sound absorption performance of silencer by adding thin plates on both sides of the resonant units to enhance its dissipation capability for sound waves. The addition of thin plates almost does not increase the size of the silencer but significantly lowers the peak frequency of the unit, achieving the goal of reducing the size of the silencer. As a demonstration, silencer was designed for target frequencies of 100 Hz, 200 Hz, 300 Hz, 400 Hz, and 500 Hz. Simulation result shows that the minimum transmission loss is not less than 16 dB, indicating excellent sound absorption performance, and is significantly better than ordinary silencers without baffles. This method provides an effective solution for reducing the size of silencers.