“Why does the sound disappear when you enter a soundproof room?” “Can’t I just use heavy walls for soundproofing?”
When you start considering buying a soundproof room, you might get confused by technical terms like “Sound Insulation” and “Sound Absorption”.
In conclusion, what protects the silence of a soundproof room is the combination of "weight (mass)" and "air layers".
In this article, we will explain the mechanism by which soundproof rooms stop sound and the “three major elements of soundproofing” that you should know to avoid failure, by breaking down technical terms.
Basics of Soundproofing: Two Powers that Stop Sound#
A soundproof room wall is not just a thick board. To stop sound, two powers with different roles are required.
1. Sound Insulation: Bouncing Back the Sound#
“Sound Insulation” is to prevent sound from passing through a wall. Specifically, it bounces back sound with heavy and hard materials such as gypsum board or sound insulation sheets.
- Image: A state where the ball (sound) is thrown at a concrete wall and bounces back without going to the other side.
- Important Law (Mass Law): The heavier the wall, the more the sound stops.
2. Sound Absorption: Absorbing the Sound#
“Sound Absorption” is to reduce the energy of sound by converting it into heat energy. Soft and porous materials such as glass wool (cotton-like material) or sponge entangle the vibration of sound.
- Image: A state where the ball (sound) is thrown at a cushion and the momentum is absorbed and it drops.
- Role: Since sound alone will echo in the room if only sound insulation is used, the sound is adjusted with sound-absorbing materials.
Point: A soundproof room is a hybrid structure that prevents sound leakage to the outside with “sound insulation materials” and clears the echoes inside with “sound-absorbing materials”.
“Strongest” Structure of Soundproof Rooms: What is BOX in BOX?#
Soundproof rooms with high performance (such as Yamaha’s Avitecs) adopt a structure called “BOX in BOX (a box within a box)”. Also, the key to that is the “Floating Structure”.
Air layers cut off the vibration#
Sound is transmitted not only through “air” but also through “floors and walls (vibration)” to the next room (solid-borne sound). To prevent this, soundproof rooms are made in a physically separated state from the walls and floors of the building.
- Floating Floor: The floor of the soundproof room rests on anti-vibration rubber, etc., and does not directly touch the floor of the building.
- Air Layer: There is always a gap (air layer) of several centimeters between the wall of the building and the wall of the soundproof room.
Thanks to this “floating state”, it is possible to drastically prevent vibration sounds like drums and footsteps from being transmitted to the next room.
Airtightness: Gaps are the Biggest Enemy of Soundproofing#
No matter how thick the wall you make, if there is a gap of just a few millimeters, the sound will leak out grandly from there. This is called “gap leakage”.
- Outlet: Since it makes a hole in the wall, it is a point that tends to be the biggest weakness.
- Ventilation Fan: A “soundproof ventilation fan (Lossnay, etc.)” that stops sound while allowing air to pass is essential.
- Door Packing: Soundproof doors are airtightly sealed with rubber packing like a refrigerator to block air.
The biggest reason why self-made (DIY) soundproof rooms tend to fail is because it is difficult to ensure this “airtightness”. Manufacturer-made soundproof rooms exhibit stable performance because they are sealed with factory precision.
Summary: Conditions for a Good Soundproof Room#
Summarizing the mechanism of soundproof rooms, the proof of performance is that the following three points are met.
- Weight (Sound Insulation): Using wall materials with solid weight.
- No Gaps (Airtight): Sealed with soundproof doors and dedicated ventilation fans.
- Floating (Anti-vibration): Vibrationally insulated from the floors and walls of the building.
Understanding the mechanism reveals “why soundproof rooms are heavy” and “why prices are high”. Next, let’s look at the “types of soundproof rooms” depending on the difference in these structures.
→ Related: Types and Selection of Soundproof Rooms | Differences in Unit, Assembly, and Construction → Back to Soundproof Room Basics Map (Top)