Room pressurization is a compliance effect that fades in unsealed rooms

Evidence

Keep in mind that there is a “Zeroth” order mode 0,0,0, commonly known as room gain or, more accurately, room pressurization mode that contributes to the modal sum. This represents a first-order compliance effect caused by an enclosed space, occurring below the first axial mode. In our graphs, we illustrate the room pressurization mode for a theoretical sealed room. However, since most rooms are not sealed, this effect will be less pronounced, and the response would actually go to zero at the lowest frequencies. — Toole, Floyd E, Sound reproduction- the acoustics and…, 1531

Categorization

• DEFINE: Clarifies the 0,0,0 mode as room pressurization/room gain, a first-order compliance effect below the first axial mode.
• QUESTION: What is the practical magnitude of the unsealed-room loss, and does door/window leakage meaningfully defeat pressurization?