This section describes sound absorption and sound insulation, which are typical sound propagation prevention technologies.
What is Sound Absorption?
Sound absorption is the process of reducing the amount of sound reflected by a material.
The sound absorption characteristics of a sound-absorbing material are expressed by its sound absorption coefficient α and its frequency response. The sound absorption coefficient α is as shown in the equation below.
Since α depends on the incident conditions of sound on the material, the sound absorption coefficient incident from any direction is generally obtained from the reverberation room method measurement specified by JIS.
What is sound insulation?
Sound insulation is the blocking of sound propagation from the outside. The sound insulation performance of a material is expressed in terms of the frequency response of the sound transmission loss TL (dB). The sound equivalent loss TL is given by the following equation
Sound transmission loss (TL), like sound absorption coefficient (α), depends on the incident conditions of sound on the material.
Example of sound propagation prevention measures (soundproof covers) using sound absorption and sound insulation technologies
Soundproofing covers using sound insulation and sound absorption technologies (materials) are used to prevent interior sound from leaking outside and exterior sound from entering the room. In the former case, soundproof walls and soundproof covers are used on the sound source side to reduce the impact of the sound source on the sound-receiving point (outside). In the latter case, soundproofing covers, etc. are used to reduce the sound from the outside.
*References
New Pollution Prevention Technology and Laws and Regulations 2016 Noise and Vibration Edition Pollution Prevention Technology and Laws and Regulations Editorial Board, ed.