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Reduce the rumble

The security business spans many different branches.

September 12, 2017  By Peter Janis

One of the most interesting is in the area of mission critical environments such as military bases, regional utilities, large industrial plants and 9-1-1 call centres. These environments all share the need for security monitoring and the challenges of ensuring effective communication.

 When it comes to audio monitoring, the challenge comes when attempting to separate the dialogue from the ambient noise.  All too often, audio playback files end up being murky, or even impossible to comprehend. The problem is the microphone. The human brain and our auditory system are superbly crafted to distinguish between what is important and what is not. For instance, you can be at a concert and somehow manage to communicate with a friend even though the sound pressure level and ambient sound energy is significantly louder that the human voice. Our ears are able to focus on the source while ignoring sounds coming from other directions. This is combined with visual cues such as body language and lip reading.

When you consider the complexity, the human brain is truly a remarkable device. A microphone is different: it has no way of differentiating between the wanted conversation and the unwanted sounds from the air conditioning system, outside traffic, background dialogue between staffers, and the combined ambient noise. A microphone flattens out all of the information and delivers the amalgam of ambient noise that reaches the diaphragm.

The solution to the problem is simple. One must control the ambiance so that the “signal to noise” ratio is acceptable and reasonable intelligibility is achieved.


When noise is produced, the sound energy reflects off of hard surfaces such as windows, doors, walls, floors and furniture. To compensate, staffers naturally speak louder to raise their voices above the din.  As they do this, the energy in the room elevates as it reflects of the hard surfaces and the noise problem self-amplifies to the point where it becomes problematic. To solve the problem, one must decrease the ambient noise by providing a release valve for the energy. This is best done by mounting absorptive acoustic panels to between 15 and 25 per cent of the available wall space. An effective solution is to distribute 2” (5cm) thick high density glass wool panels around the room.

Placement is often not critical as the ambient noise is everywhere. Increasing the density of the panels in areas that produce a higher noise level will help contain it. If wall space is limited, suspending clouds or baffles from the ceiling is a highly effective option as sound energy penetrates the acoustic panel from both sides, thus effectively doubling the performance. One must simply pay attention during installation to ensure the acoustic panels do not interfere with the lighting fixtures, fire sprinklers and ventilation systems. Once installed, the ambient noise will be significantly reduced and the comfort level for staffers will be enhanced. This not only makes the space more comfortable, it also reduces communication errors.

It is worth mentioning that operators suffer a major health concern with their headsets when in noisy environments. There is a misconception that with a headset, one can better control the ambient noise as the voice and headphone is essentially connected to the operator. The problem here is that when multiple operators are speaking at the same time, their voices compete and they instinctively circumvent the problem by increasing the volume of the headset going to their ears.

What they do not realize is that they are almost always listening to sound pressure levels that far exceed the safety standards set by OSHA (Occupational Safety and Health) and this level of exposure can lead to permanent hearing loss.  Reducing the ambient noise is not only the best solution, but truly the only viable one.  

Peter Janis is the president of Primacoustic, based in Port Coquitlam, B.C. (www.primacoustic.com).

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