Soundproofing ventilation devices can block sound while allowing free airflow simultaneously, which have many important applications in daily lives. In this work, we theoretically design and experimentally implement a broadband low-frequency acoustic meta-window. The meta-window is composed of a central rectangular open area and 12 surrounding identical channels. The total ventilation area is 220 cm2. Interestingly, with a deep subwavelength thickness of 4 cm, such a meta-window can exhibit a large acoustic bandgap, leading to the effective blocking of more than 90% of the incident sound energy in the broad range of 605–1050 Hz. By cascading such acoustic devices, the sound blocking effect can be further improved. Our work realizes a large-area and ultrathin ventilative meta-window with the function of broadband low-frequency acoustic insulation. [ABSTRACT FROM AUTHOR]