[Soundproofing knowledge] About the loudness of sound and the four sounds that are targeted for soundproofing

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This time, which is the first time, I would like to briefly explain "soundproofing".

1. ㏈ (sound volume)

First of all, before explaining soundproofing, I would like you to relate the number of sounds you feel in everyday life in units of ㏈.

(Source: Types of sound level meters and guidelines for noise levels )

As you can see from the table above, many people feel that it is "noisy" around 70 to 80 ㏈, such as in the subway. Even in a quiet office, there is about 60㏈ (libraries are about this level), and even in a residential area late at night when there is almost no sound, there is about 40㏈ . Until I studied soundproofing, I once had the idea that "completely soundproofing will result in 0cc ". About 60 ㏈ occur in everyday life.

If you search the internet for examples like this, you will find many, so if you are interested, please take a look. There are various degree examples, and if you can see more than one, I think you will gradually understand the feeling of ㏈.

2. There are 4 types of sound that are subject to soundproofing

Soundproofing is a general term that summarizes four types of meanings: sound absorption, sound insulation, vibration isolation, and damping. I will briefly explain each.

Sound absorption

Sound absorption refers to the mechanism by which sound generated by shaking air passes through a sound absorbing material and is internally converted into heat energy by friction with the sound absorbing material, thereby attenuating the sound. This means that it is not reflective. As a familiar example, glass wool, which is also used in houses, can be used as a sound absorbing material. Also, perforated boards with many holes in the walls of school music rooms and gymnasiums are sound absorbing. It has a structure in which the sound is allowed to enter the interior through the opening of the holes, and is attenuated by the internal sound-absorbing material and air layer. General sound-absorbing materials are composed of porous or interconnected air bubbles, so energy cannot proceed in a straight line inside. Therefore, frictional heat is generated by repeated collisions, but the sound absorbing material itself does not become hot. Conversely, it can be said that the sound absorption coefficient is low if the material is not porous but composed of closed cells.

②Sound insulation

While sound absorption attenuates sound as it passes through, sound insulation refers to a mechanism that reflects sound generated by shaking the air without allowing it to pass through. Concrete will be the most familiar material, but if you speak out in a tunnel, it will reverberate. Concrete does not have small holes that allow sound to pass through like sound absorbing material, nor does it have sound absorbing material or air inside to attenuate sound, so sound can bounce back and prevent sound leakage to and from the outside. prevent.


Vibration isolation refers to a mechanism that reduces the vibration (sound) transmitted by the vibration of an object, which is different from the sound generated by shaking the air. For example, suppose the colliding material is the foot and the colliding material is the floor. At this time, the impact from the foot is directly transmitted to the floor, and the sound of walking is transmitted to the floor vibration and reaches the room and the room below. By placing carpets and cushions on the floor as anti-vibration measures, the vibrations transmitted from the feet to the floor can be suppressed, thereby mitigating the vibrations in the room and the room below.


Vibration damping is a mechanism that suppresses sound by absorbing vibration (sound) generated by the vibration of an object and preventing it from vibrating. In contrast to vibration isolation, which prevents the sound of a vibrating object from being transmitted to other objects, damping refers to preventing (suppressing) the vibration of the object itself. A cymbal produces sound by vibrating, but the principle is that if you suppress the vibration with your finger, the sound disappears. As an example of damping material, I think there is something like rubber on the four corners under the washing machine in your house. This will act as a damping material to reduce the shaking of the washing machine.

 The above is a simple explanation, but if you want to take measures against noise caused by vibrations in the air, such as the voice of cicadas or the sound of a motor, sound absorption and sound insulation are the way to go. If you want to take measures against noise such as footsteps and vibrations of machines such as outdoor units that are transmitted to the ground, it is important to identify and combine four types of soundproofing measures, such as anti-vibration and damping measures. In the case of an outdoor unit, for example, it can be said that there is both air propagation and vibration coming from the motor itself, so it is effective to take two measures, sound insulation and vibration isolation, to reduce the noise to the next house. It can be said.

There is also something to be aware of. For example, when playing a musical instrument in a room, there is a case where only sound insulation material is installed to block the sound from the room out of consideration for the neighbors. It is true that the sound insulation effect can reduce the sound outside the room, but the sound insulation will cause the sound to reverberate excessively inside, making the room quite noisy. In the concrete tunnel I used as an example when explaining sound insulation, the sound that passes through the tunnel echoes and becomes louder than the sound that a normal car passes through. Such excessive reverberation can actually make the sound louder than the sound of the instrument itself, making the room quite noisy, and the amplified sound can end up being a nuisance to the neighbors. Therefore, by combining sound absorbing material on the inside and sound insulating material on the outside, it is an optimal measure to suppress the reverberation inside the room and also suppress the transmission to the outside.

Products on our site corresponding to four types

<Sound absorption>

<Sound insulation>

<Sound absorption>


Acoustic articulator panel

<Vibration isolation/damping>

The above is just an example, and we have a wide variety of colors and sizes, so please check the product page and try it out.

I hope that this article has been of some help to you.

We will continue to distribute information to help everyone in the future, so thank you for your support. Excuse me for this time. thank you very much.


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