Phase 1

• After identifying characteristics (ratio of sound absorption, a diffuser, a radiation ratio etc.) of a room that damages are expected, a type of sources generating noises and sound pressure are selected. The most exact data for sound pressure of sources generating noises are provided by a company and it may be obtained by calculation as necessary.

• Parameters required for calculating noises a static pressure, wind pressure, an output, a fan type, RPM, temperature for use, allowable pressure loss (mmAq)

Phase 2

• Natural noise reduction and the generated noise during noise is transmitted into the indoor space are reviewed.

• Check items for natural noise reduction an elbow, a chamber, a straight duct and a self noise

Phase 3

• The required sound reduction is calculated by calculating and comparing noise of a duct with the allowable noise level (NC, NR) of the determined room with reference to calculation data for characteristics of a room, the generated noise and natural noise reduction that were reviewed at the phase 1 and 2.

Phase 4

• After reviewing the allowable pressure loss based on the calculated required reduction of noise, the standard dimension proper for air volume is selected. The self noise may be prevented only when the passing-through wind speed of a sound absorber is equal to or less than the passing-through wind speed of a duct and the proper noise reduction performance of a sound absorber may be maintained.