Subterranean builds have many features and benefits. Wrapping a concrete barrier with earth and lots of it is a wonderful thing and very cost effective. Next to poured concrete, I can not think of a better barrier material. Surrounding your room with tons of earth can provide for high STC ratings and a very quiet room inside, Care must be taken to prevent vibration energy transmission from the earth itself but this is a small price to pay for the isolation capacities exhibited by tons of mother earth.
On the room inside, we must make sure we have the correct room size and volume to match the usage and as always paying particular attention to the low end. In rooms that above ground, low frequency energy cab bleed into adjacent rooms and structural openings. This “bleed” has the effect of providing a type of pressure release valve that lets some of the unwanted low frequency pressure escape from the room thus reducing amplitudes of modal structures. This will not occur with a subterranean build where the exterior of the room is wrapped in tons of concrete and earth. Care must be taken to make sure that this excess energy does not pass to other parts of the structure. Since less can energy can escape, we have more energy to manage within the room itself.
This project will be a two channel listening room with all surfaces properly manged for low middle and high frequency absorption along with ceiling, front/rear wall diffusion. Isolation technology will be employed to isolate energy from the structures above the listening room. Low frequency energy is like water, it will look for the weakest link in the structure and go through that weak area. With earth and concrete surrounding all the walls, we must pay particular attention to the density of the first floor flooring structure. Since this will be the weakest link because of its much lower density than earth and concrete, we must increase the density and mass in a manner that minimizes transmission of noise. We will provide more text, photo, and video updates as the project moves forward the second half of 2016.