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Do you think that In-Ear Monitors would work for firefighters?

post #1 of 3
Thread Starter 

Firefighters sometimes have trouble hearing their radios because they are working in a high noise environment while wearing layers of headgear. In-ear-monitors may solve some of the problems firefighters now experience. What do you think?

Your experience and insights may make it possible for firefighters to make IEMs that are specifically designed for their work. (please note that this is non-profit effort...and if you want to get involved in making IEMs for firefighters then that might be a great help)


Some goals:
1] allow firefighters to hear radio traffic in high noise environments
2] stay in place
3] be cost effective (relatively inexpensive and/or have a long service life)


Some questions that you might be able to help answer include:

Do IEMs work well in high-noise environments?


Do some sizes and/or shapes of IEMs work better than others?


Once inserted, do IEMs stay in place?


If they don't, do you have any ideas or advice on how to ensure that they will remain in place?


How sensitive are IEMs to moisture (water), oil, and dirt?


Can they be cleaned?


Are there any ways to protect IEMs from damage that might be caused by water/oils/dirt?


How long (with proper care & handling) can a pair of IEMs be expected to last?


In what ways do IEMs fail?


What don't you like about IEMs?


How often do IEMs need to be refitted in order to ensure proper function?


Do you have any advice on how to improve the function & service life of IEMs?


Can IEMs be shaped to lessen or avoid the kinds of physical interference that might knock them loose?


Would something other than an IEM work better?


What other questions need to be addressed?


Please let me know (via the thread) if you need additional information.




The following images are intended to show some of the gear-related physical interference problems with wearing audio devices in or on the ears:



This is not fully geared-up (the SCBA tank, hoses, controls, and mask interface are not shown), but it may give you an idea of what is likely on top of a firefighter's ears.



The big beige sock is a fire hood - it's made of a soft fire resistant material and mainly acts to prevent flash burns.

Once the fire hood is on it may be difficult, impossible, or dangerous for the firefighter to access an IEM. If the firefighter is not in a safe area then removing gloves and opening the bunker coat (etc.) could result in a serious burn, so it's important that the IEMs remain in place.



This is one style of SCBA mask - there are many different designs - but you may be able to imagine how the mask straps might catch on an audio device.



These are some Orange County Fire Authority firefighters during a training exercise. They are preparing to use a gas powered saw to cut through a metal wall that is at the end of a concrete pipe. Firefighters use noisy equipment and work in environments that can be very noisy.

post #2 of 3

I think in general military and firefighting forces can use bone conduction audio devices instead of something like an IEM because they still need to hear commands, cries for help, etc.  The bone conduction process leads to poor sound quality, but most people in the business are more concerned about safety rather than sound quality.


Most police forces in my area use an IFB custom molded in-ear piece.  I think they have two way versions now which would be much more durable and have a better seal than almost any IEM out there.


As for fit I know Tyll rides his motorcycle with IEMs in sometimes.  He says that most customs will not fit with a low profile helmet and he usually ends up using a pair of Etymotic ER-4PT.


Here is a link:



Obviously due to wear and tear a headphone of any type used in firefighting conditions is going to have to be robust.  That means having strain reliefs at both ends of the cable, detachable cable, heat shrink around the strain relief, as well as a readily available repair service.

post #3 of 3
Thread Starter 

Yes, you are right, and there are various forms of tactical headsets available for use by military (particularly special operations forces), law enforcement, and firefighters.

In fact, one of the firefighters I am working with now uses a tactical headset from Peltor that is also used by special operations forces (see photos below). There are, unfortunately, various issues associated with the in-ear, over-ear, and bone conduction headsets that reduce their effectiveness in the most critical firefighting applications in which an SCBA is also used.


Before I go into that I'd like to point out that some of the currently available tactical headsets may be appropriate for certain firefighting use cases, such as wildland fire fighting. It's when a firefighter gears up with an SCBA, possibly in conjunction with a HAZMAT suit, that certain "human factors" problems rise to the surface.


Bone conduction transducers (for audio input and output) is a very interesting subject. Two of my favorite references on bone conduction transducers are from the US Army.
The excellent "Bone Conduction: Anatomy, Physiology, and Communication," available at: http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA468459
and "Bone Conduction Head Sensitivity Mapping: Bone Vibrator," available at: http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA436360


Three issues associated with bone conduction headsets are 1] Physical interference, 2] Discomfort, and 3] Sensation, Perception, and Cognitive workload

Bone conduction headsets are often larger than conventional "air interface" headsets in part because the transducers must be pressed against the head to effectively transfer sound energy. This usually involves some kind of spring device and harness. According to the US Army research (referenced above) the most sensitive location for transducer placement is an area in the upper jaw (the points are mapped in the report) that is, unfortunately, within the footprint of the SCBA mask seal. This presents a physical interference issue.


The spring loaded transducers that press against the head can result in hot spots - pressure points that become painful. While firefighters are tough people, like all humans they react to pain. In the case of equipment generated hot spots, there is a tendency to remove or adjust the equipment periodically to relieve the discomfort. This serves to reduce operational effectiveness in that time spent adjusting (or removing and replacing) equipment is a distraction from other activities. It may also mean that an important signal (such as a command issued by radio) is missed because the communications gear is not in place all the time.


Perhaps the biggest issue relates to "sensation, perception, and cognitive workload." Humans do not have an inherent ability to make sense of speech-based communications: we learn how to do this. Processing speech is a huge cognitive load, which is one reason why talking on the phone while driving can impair one more severely than being drunk. In a high noise environment, picking out the signal from the noise requires even more cognitive effort. For firefighters this means that more of their gray-matter resources must be focused upon hearing and processing sounds that may contain important information. This reduces their ability to develop and maintain the kind of mental models that provide situational awareness.


The thinking here is that by controlling which sounds reach the ear we can do something about the stress and cognitive workload of firefighters. With good sound control (such as the ability to block most ambient noise) we have the option of switching between signals (such as radio traffic and/or warning sounds) and environmental sounds. Does this make sense?


You mention using IEMs with a motorcycle helmet...can you describe the issues in more detail? Do the custom IEMs stick out too far, is it the connector, or some other issue that causes trouble?



In this image, a Peltor headset with a Push-To-Talk control is clipped on to a bunker jacket. Note how the wires are passed through various loops, etc., to keep things from dangling and tangling.



Here you can see the "earbuds" of the Peltor device. It is my understanding that this tactical headset, which is used by certain military units, filters out impulse noise...the type generated by weapons when they fire. Other sounds, such as might be experienced by firefighters, are not filtered out.


Below is an image borrowed from www.tacticalcommandstore.com  showing their TABC II Tactical Assault Bone Conduction Headset:


Notice the point of contact made by the transducer that is located forward of the ear.

This is a pretty cool design that probably works well for many applications - but it doesn't meet the needs of firefighters.


Thanks! I appreciate the response. Please feel free to critique anything I've said here...you won't hurt my feelings and it's important to get this stuff right.

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