A Soundproof room like a Thermos

Others

Since there happened to be a Thermos on the author’s desk, I would like to discuss how the soundproofing effect might be if a soundproof room were designed in a shape similar to a thermos.

Hollow double walls

First, a thermos has a double structure with an outer layer and an inner layer. The space in between is said to be a vacuum. This design is for insulation purposes.

In soundproofing design, there is a term called “Hollow double walls”. It literally means having two layers of walls with an air gap in between.

Hollow double walls are said to be a concept that provides high soundproofing performance. While a thermos has a similar structure, unlike a thermos, hollow double walls are not vacuum sealed but are connected through air.

*A typical hollow double wall structure has various issues as a soundproofing design.

While these issues are not covered here, it is true that a soundproof room with a vacuum would offer high soundproofing effectiveness (though its feasibility is low)

What would happen if a cylindrical shape were applied to a soundproof room?

What would the soundproofing effect be if a cylindrical soundproof room were created, similar to a thermos? Since soundproofing involves reflecting sound, when noise from outside the cylindrical soundproof room hits the room, it would scatter due to multiple reflections.

I believe this would achieve high soundproofing effectiveness. Additionally, because a cylindrical shape involves bending panels into a curved, rather than flat, plane, it offers greater rigidity compared to flat panels. Higher rigidity generally means better soundproofing performance.

On the other hand, what about the interior?

If we represent the sound generated inside with arrows, it would reflect as shown in the diagram above. This means that the reflected sound may converge at a single point, creating areas where the echo is amplified.

This is undesirable in the design of a soundproof room.

Examples of a soundproof rooms using curved (R-shaped) designs

Previously, there was a design case of a spherical piano soundproof room by SONORA’s technical advisor, Mr.Mitsuru Yabushita (YAB Corporation)

As mentioned earlier, while this is not ideal for controlling internal reflections, the external shape is effective for soundproofing. By adding absorption and diffusion units on the interior, the design achieves pleasant indoor acoustics, as shown in the photo.

With such innovations, it is possible to turn a disadvantage into an advantage

Summary

• If there were a soundproof room with a vacuum between the walls, its soundproofing performance would likely be very high.
• A cylindrical shape is effective as an external soundproofing design
• A cylindrical shape is not suitable as an internal wall design
• It is also possible to design by leveraging the shape