Sound Absorption is a technique where in various absorbent materials are strategically used to absorb sound to avoid unwanted reflected sound waves within a room or space. The main reason to use this technique is to reduce reverberation time (RT) for making the speech clearer. There are two rating methods prominently used across the world.

(a) NRC (Noise Reduction Coefficient): The term is majorly used within United State and defined as part of American Standards. The rating is unitless and it is a coefficient and the ranges are from 0 to 1. Higher the average NRC is the better will be the absorption property of the product.

(b) Weighted Absorption Coefficient: It is prominently used across the world and defined as part of ISO Standards. Similar to NRC, the rating is unitless and the ranges from 0 to 1.

Sound Insulation is a technique used to stop sounds transmission from one room to another. The main reason for this technique is that it ensures privacy within the room, cabin, studio, cinema, home theatres, conference rooms, auditoriums, sports auditoriums, halls etc. Sound insulation is required to stop the sound going out from the said premise or the area as the excessive sound going out could disturb the surrounding atmosphere. Like sound absorption, there are two main rating methods.

(a) STC (Sound Transmission Class) : As per American Standards which is used across the world, majorly within United States, STC is the capacity of any product to block the sound. It is a single number rating and measured in Decibels (dB).

(b) RW (Sound Reduction Index) : It is majorly used outside the United States and is a part of ISO standards. It is again similar to STC and it is a single number rating measured in Decibels (dB).

Vibration Isolation is a technique, where in resilient materials such as rubber, springs etc. are used to stop transmission of vibrations from source to other mediums. The main reason of using this technique is to isolates the source from spreading extra vibrations, indirectly blocking or reducing noise or sound emission. There are two main methods for measurement of vibrations.

(a) PPV (Part Particle Velocity): It is measured in m/s (meter/second) and is used to measure vibration transmission from source to other mediums.

(b) VDV (Vibration Dosage Value): It is measured in m/s^(-1.75) and is used to measure dosage value in context to humans.