NRC: Noise Reduction Coefficient

Introduction: The NRC, Noise Reduction Coefficient, is the average of the levels of absorptiveness in a material at four different frequencies; 250, 500, 1000, and 2000 Hz. If a material has an NRC of 0, it will reflect sound. If it has an NRC of 1, it is perfectly absorptive. These numbers can be converted into a percentage, therefore ranging from 0% to 100% in absorptiveness. (Noise Reduction Coefficients (NRC) Ratings for Common Building Materials & Products, n.d.) In order to soundproof a room, one must keep in mind that blocking an air path using a regular wall, ceiling, or door will not entirely reduce the sound. Vibrations will continue to travel through a solid, specifically when a material provides an unobstructed path for it to follow. Therefore, in order to control sound effectively, one must block sound paths and vibration paths. (Miller & …show more content…
The purpose of this experiment is to test these different soundproofing materials which might be applied in a music practice room at a home. Common soundproofing materials which can be found at every day home improvement stores will be tested for their abilities to absorb sound at different frequencies. The sound source will be placed in the box and measured externally for sound transmission. The different materials will then be lined along the interior of the box individually and tested for their respective levels of transmission at three different frequencies. This is done because the sound of different frequencies passes through different materials at a different rate. The independent variable is the material through which the sound is passing, while the dependent variable is the number of decibels passing through the material. Based upon a tactile observation and the NRC (Noise Reduction Co-Efficient) of 0.9, recycled batt insulation will absorb the largest number of decibels when encountering any