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Sound propagates from its source as a pressure wave, which then interacts with the structures around it through vibration. In the world of noise control, if the sound cannot be reduced directly at the source, the waves will continue on their journey in direct or reverberant paths. Understanding these sound paths is critical for reducing unwanted sound.
The most straightforward sound path is, appropriately, the direct sound path. When unimpeded, sound moves in a straight line directly to the listener. Direct sound is dominant while close to the source. As sound travels, the inverse square law comes into play. The energy twice as far from the source is spread over four times the area, creating one-fourth the intensity.
Clearly, distance can be used to mitigate noise on its own, but sound doesn’t only travel in one direction.
The reverberant sound path is one that soundwaves utilize only after being reflected.
In our previous blog article, What is Reverberation? Hear for Yourself!, we discuss how reverberation can be harnessed to create a better listening experience with the utilization of properly-tuned reflectors, diffusers, and optimally-placed absorbers (to limit reverberations after a first-order reflection).
Sound that transmits through other surfaces is also a noise concern. Walls, floors, ceilings, and other barriers, when not properly attenuated, allow sound into adjacent spaces. STC, or sound transmission class, is a number that describes how well partitions reduce sound transmission. While perceived speech intelligibility will always be dependent on more than one factor, STC provides a rule of thumb when it comes to how much a particular partition can mitigate the transmission of sound.
The final path to discuss is diffracted sound. Diffraction is the bending of sound waves around obstacles and through openings. As an example, if a listener is in a seat with an obstructed view at a theater, sound will bend around the object in front of the seat, and that listener will hear diffracted sound. Low frequencies are more easily heard around obstacles than high frequencies. While partitions can act as blockers as discussed above, it is important to consider that some sound can move around them and be heard in unwanted places.
There is much more to acoustic treatment than simply absorbing or blocking. To truly tune a space, it is best to have a discussion with an acoustical expert. Both knowledge and experience are key factors when designing an effective acoustic environment. The acoustic experts at Oeler Industries have the knowledge and experience to create a tailored solution for any noise mitigation needs. Want to make your building a great place for conversation? Get in touch with us at 412-884-3000 or click here.