"My neighbors are noisy, so I pasted sound-absorbing sponges on the wall. But there’s no effect at all…"
This is the No. 1 common failure story in DIY soundproofing. Many people confuse the roles of “sound-absorbing materials” and “sound-insulating (blocking) materials.”
In baseball terms, these two are as different as a “pitcher” and a “catcher.” In this article, we’ll explain the basic knowledge for creating a correct soundproof wall.
The Role of “Sound-Absorbing Materials” that Many People Misunderstand#
Those bumpy urethane sponges sold on Amazon and elsewhere are “sound-absorbing materials.”
The Job of Sound-Absorbing Materials: “Reducing” Sound#
Sound-absorbing materials are made of porous (hole-filled) materials. When sound enters these holes, it turns into heat energy through friction, reducing reflected sound. In other words, their main role is “to suppress the resonance (echo) of a room.”
However, sound-absorbing materials are sparse, so they let sound “pass through (transmit).” If you only paste these on a wall, the sound will pass right through the sponge and reach the next room.
What Actually Stops Sound: “Sound-Insulating (Blocking) Materials”#
The Job of Sound-Insulating Materials: “Reflecting” Sound#
On the other hand, it’s the role of “sound-insulating materials” to prevent sound leakage to the neighbor. “Heavy and hard” materials such as lead sheets, sound-insulating rubber mats, and gypsum board fall into this category.
Sound-insulating materials reflect sound. By reflecting it, they keep sound from passing to the other side of the wall (increasing transmission loss).
However, if you only paste sound-insulating materials in a room, the sound will continue to bounce around inside, resulting in an uncomfortable room that echoes like a bathroom.
The Strongest Soundproof Wall Structure: A Sandwich of Insulation and Absorption#
To create an effective soundproof wall, you need to combine these two.
- [STEP 1] Insulate/Block: Paste “sound-insulating sheets” or “gypsum board” on the wall to create a wall that reflects sound. This prevents leakage to the next room.
- [STEP 2] Absorb: Paste “sound-absorbing boards” or “sponges” over the insulating material (indoor side). This absorbs the sound reflected by the insulating material and adjusts the resonance in the room.
Ideal Order#
[ Wall ] - [ Insulating Material ] - [ Absorbing Material ] - [ Human ]
By following this order, you can prevent sound leakage while creating a clear acoustic environment.
Summary: Understand Material Characteristics for Smart DIY#
Discard the superstition that “pasting sound-absorbing material will provide soundproofing.” If you want to stop sound, use “heavy things (insulating material)”; if you want to eliminate resonance, use “light things (absorbing material).”
Choosing and distinguishing materials according to your purpose is the shortcut to success in DIY soundproofing.