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Ambiences & Acoustics: Improving Communication in 9-1-1 Centers

Author: Peter Janis

Copyright: Copyright 9-1-1 Magazine, Feature Content

Date: 2017-02-15
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The Hennepin County (MN) Communications Center in Minnesota. Photo via Winbourne Consulting, LLC

A 9-1-1 center is a hectic environment that never sleeps.  Calls simultaneously come in from multiple phone lines with dispatchers competing to hear themselves over the din. When a major event occurs, voices automatically raise as stress levels elevate. As more emergency phone calls come in, dispatchers further elevate their voices in an attempt to hear themselves over the other dispatchers and better communicate with the caller.  As the event intensifies, communication between dispatchers, emergency services such as police, fire, ambulance, and first response teams intensifies. Instructions from supervisors add to the already heightened levels of anxiety, and voice levels escalate further.


Our brain compensates for a noisy environment by combining clues such as the directivity of the sounds arriving at our two ears, lip reading and body language in order to discern the message.  For someone at the other end of a telephione line, all of these clues are lost. The headset microphone flattens out the information – mixing the important stuff with the noise - reducing intelligibility and hampering communication.


To make matters worse, many 9-1-1 centers follow typical office construction with hard – reflective surfaces such as walls and ceilings made from gypsum board, windows, large arrays of video screens and either tiled floors or concrete that is surfaced in a thin industrial carpet.  Sound from voices and other ambient polluters such as HVAC systems, outside traffic or even emergency alarms reflect off these hard surfaces, creating a dense echo known as the reverberant field. Because there are no walls separating the zones, the noise pollutes the entire facility. As more dispatchers log on with competing calls, the voices along with the ambient noise level in the room combine and ricochet off of the hard surfaces, elevating the noise levels and a cacophony self-perpetuates to the point of breaking. Communication becomes strained, patience wears thin and efficiencies suffers. Tempers flare, mistakes are made, disasters occur.

Depending on the size of agency and jurisdiction, 9-1-1 centers can consist of anywhere from three to four dispatch consoles to more than a hundred when servicing large metropolitan areas. The 9-1-1 center can be a standalone facility or part of a police or fire headquarters or other agency building.  Larger centers will usually have dedicated personnel to answer 9-1-1 phone lines, business lines, or handle the radio consoles while in smaller centers the personnel will be often be tasked with doing it all.  The primary mode of communication is through a head-worn headset. These are of course made up of a microphone and headphones.  The microphone is used to transmit the important message while somehow being tasked to ignore the ambient noise that abounds.  Although this sounds like a simple task, it is in fact a complex challenge. 

The human auditory system – ears and brain – is an amazing device that is able to discern what is important while ignoring what is not. We have all experienced the difficulty of having a conversation in a noisy restaurant where exceedingly loud conversations from nearby tables make it practically impossible to hear what is being said by the person across the table. Our brain compensates for the environment by combining clues such as the directivity of the sounds arriving at our two ears, lip reading and body language in order to discern the message.  For someone at the other end of the phone, all of these clues are lost. The headset microphone flattens out the information – mixing the important stuff with the noise - reducing intelligibility and hampering communication. Broadcasters have known of these problems for over 100 years and acoustically treat their studios for this very reason. They want to ensure the broadcast message is not only being effectively transmitted, but understood by the listener.  In 9-1-1 centers, the ‘communication’ problem is further exacerbated by poor cellphone connections, the caller’s extreme anxiety and reduced ability to focus and the commotion surrounding the emergency that may be at hand.

The noise within the room is not the only concern. In smaller 9-1-1 centers, the combination of first response teams opens the door to noise from emergency vehicles or other events that may be simultaneously occurring in other rooms. Noise transmits through ineffective T-bar ceiling tiles, into the plenum and then exits and pollutes other areas. This not only increases ambient noise in the call center, but also affects privacy in adjacent offices and meeting rooms.

The good news is that solutions exist to reduce noise and improve communication.  It comes in the form of acoustic treatment. By mounting high performance absorptive acoustic panels to between 17% and 25% of the wall surfaces, ambient noise can be greatly reduced. 

Care should be taken on selecting the type of panel as these differ significantly.  For instance, low-density open-cell foam panels are sometimes considered due to their low cost, but the low density means that they typically will only absorb higher frequencies, leaving the all-important voice range untreated.  The other problem is that foam panels are not Class-A fire rated for safe use in public places or in new construction. A better choice are panels made using glass wool. The most effective employ high-density 6lb per cubic foot glass wool that is encapsulated with micromesh and edges are resin hardened to prohibit dusting. Soundwaves or vibrations penetrate the panels causing the minute fibers to vibrate, which in turn generates heat. This energy conversion is known as thermodynamics.  Glass-wool panels are typically wrapped in an acoustically transparent polyester tweed and mounted to the walls using Impalers. Installation is as easy as putting up a picture. Credible manufacturers will provide flame spread and smoke development tests (ASTM-E84) along with acoustic tests that have been performed by independent laboratories.  By reducing the reverberation time below 0.7 seconds and absorbing sound energy in the voice range between 250 Hz and 2 kHz will assure maximum intelligibility.

Placement is not critical as the noise we are attempting to subdue is omnipresent. Panels are generally mounted wherever available wall space is at hand.  For facilities where wall space may be limited, acoustic panels known as ‘clouds’ are suspended from the ceiling, above the dispatchers using eye hooks, aircraft wire and height-adjustable hooks. Should the facility be constructed with a T-Bar ceiling, ineffective fiber-board panels may be replaced with high-density 6lb ceiling tiles that retrofit into existing T-bar systems without the need of tools.  These provide significantly greater absorption while generally being more esthetically pleasing. Where privacy or noise containment is needed, ceiling tiles are available that combine gypsum board with high-density glass wool. These panels work double duty by adding a mass component to stop and contain sound while controlling ambient noise via the absorptive surface.

Treating the room will reduce echo, lower ambient noise levels and improve intelligibility. It will also help localize the sound so that it does not travel and pollute adjacent areas.  This will improve communication between dispatchers, other team members and with the person on the other end of the phone.   Improving the work-place acoustics will ultimately help keep stress levels under control and improve overall efficiencies.


Peter Janis is the President of Primacoustic.  The company has been involved with acoustics for over 20 years, producing acoustic panels for use in all types of installations. Primacoustic clients include NBC Olympics, Target, Renault, Cisco Systems, US Armed Forces and Sony among others. For more information visit


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