Trane TRG-TRC007-EN manual Reflected Sound

period three

Acoustical Analysis

notes

Reflected Sound

Figure 50

Finally, some of the incident sound energy (Wi) bounces off of (or is reflected from) the material. Reflected sound becomes especially important when the sound source and the receiver are located in the same room.

Consider a mechanical equipment room that contains a water chiller, pumps, and other sound sources. Often the walls of the equipment room are constructed of masonry—either cement block or poured concrete. Neither of these materials absorb or transmit very much of the incident sound energy, so most of it is reflected back into the room. The reflected sound adds to the sound coming from the source, greatly increasing the sound level in the room. The best way to reduce reflected sound is to add an absorptive material to as much of the walls, floor, and ceiling as possible.

On occasion, reducing reflected sound may also lower the sound levels in adjacent spaces. Using the equipment room example, reducing the reflected sound energy lowers the sound level in the equipment room. Given a fixed transmission loss for the walls, this will result in a decrease in sound that travels to the adjacent space. Said another way, if it is quieter in the equipment room, it will be quieter in the adjacent spaces.

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