In certain situations, an outside space must be protected from the surrounding outside noise. Encapsulation, barriers, increased distance or masking the noise source are some possible solutions.
General rules of thumb for controlling outside noise:
- By doubling the distance from a noise source,
the level is reduced by 6 dB, a clearly noticeable amount. The
reduction will not be experienced to this extent with a line source,
such as a railroad or freeway (the reduction is around 3 to
- A barrier must block the line-of-sight between
the source and the receiver in order to be effective.
- You will typically not need a barrier with
a surface weight/density greater than four-pounds/square foot,
as long as there are no openings in the wall.
- It is difficult to reduce the noise by more
than 10 dB with a barrier wall.
- Noise barriers can be solid walls, berms
or a combination of the two.
- The noise wall must be continuous with no
openings to be effective. If air is going through the wall, so
- Vegetation, such as trees and bushes, provides
very little, if any, noise reduction.
Area of concern: A column burial area with a meandering path
Additional information: This space needed to facilitate a solemn and contemplative setting while minimizing distractions from a nearby street. Originally, a concrete block wall was used, but the results were not sufficient.
Questions to ask client:
- Describe the problem.
- Describe the ambient noise conditions.
- Are there any existing barriers?
- What is the desired result?
- The cemetery is next to a relatively busy road. The traffic noise is distracting to visitors who expect a quiet, intimate setting.
- Aside from the traffic noise, there are no
other major noise sources in the area.
- A concrete block wall was used, but the results were not sufficient.
- The desired result is a relaxed, meditative atmosphere that is aesthetically consistent with the rest of the space.
Evaluation: Since it was not feasible to increase
the barrier wall height, a sound masking system (that is typically used
in an office environment) was implemented in this case. To blend in with
the atmosphere, rock speakers that generated pink noise were placed
along the meandering path. Water features served as additional atmosphere
enhancers, and helped to make the masking system sound more natural. These fountains
also eliminated hot and cold zones and created a consistent noise
through the entire space. Water features alone would only work when a visitor was standing directly next to the water.
Additional comments: In many cases, the best outdoor solution is a barrier wall. Other solutions include encapsulating a noise source (such as an emergency generator) and adding distance between the receiver and the noise source.