What is Sound Insulation (Transmission Loss)?
What is Sound Insulation (Transmission Loss)?
Transmission Loss (TL) refers to the ability of a material, such as a wall, to prevent sound from passing through. When sound waves hit a wall, the portion that doesn’t penetrate the wall and instead reflects is known as “reflected sound energy,” while the portion that does pass through is called “transmitted sound energy.” This balance affects noise control and sound leakage within spaces.
In English, transmission loss is denoted as “TL” and is commonly calculated to measure sound insulation effectiveness. Materials like sound-insulating panels, concrete walls, metal sheets, and boards are examples of effective barriers.
Units and Standards
Sound levels are now internationally standardized and measured in decibels (dB).
For specific information on “Noise Regulation Laws” or “Occupational Safety and Health Regulations,” please contact us directly.
The “Mass Law” Principle
The effectiveness of a material in blocking sound (transmission loss) increases with its weight and thickness. This basic principle, known as the “Mass Law,” suggests that denser and thicker materials provide better sound insulation.
The formula to calculate transmission loss is as follows:
TL = 18 log(f・M) − 44
(where f = frequency, M = surface density)
The transmission loss increases with both material weight and sound frequency. At higher frequencies, transmission loss tends to be greater, making it easier to block high-frequency sounds.
Key Points to Consider
- Heavier and thicker materials typically offer greater sound insulation.
- Achieving results beyond the mass law is challenging.
- Effective lightweight soundproof materials don’t exist.
- Terms like “sound insulation,” “soundproofing,” “sound absorption,” and “vibration” each have distinct meanings.
- A safety margin is crucial to guarantee sound insulation performance.
- High-frequency sounds are easier to insulate, often with lower installation costs.
- Low-frequency sounds are harder to insulate and often incur higher installation costs.
- Analyzing the frequency of the sound source and selecting materials accordingly is essential.