Pro-Ears Dimension 2 "Pro-Mag" Electronic Hearing Protection/Amplification System

The Case for Hearing Protection

A large percentage of that most critical skill known as safe shooting involves the safe handling of firearms.  But an equally large percentage has to do with managing the environment in which one shoots.  Hunters take pains to dress in such a way that the don't become accidental targets of other hunters.  Target shooters go to extremes to ensure that their backstops are substantial enough to safely stop their rounds.  That being said, there is one environmental factor that affects all shooters regardless of what they shoot or where.  Specifically, we're talking about the extreme levels of noise and blast produced by modern firearms.  Indeed, there really are only two types of shooters in the world:   Those who've made a point of wearing  the proper hearing protection and those who have suffered or will suffer hearing loss as a result of wearing either inadequate hearing protection or  no hearing protection at all.  It's a widespread problem whose magnitude approaches pandemic proportions:  In the United States, hearing loss

affects between 25 and 28 million people - that's nearly one out of ten, folks!  Ok, ok, we're being a little dire here; the most common cause of hearing loss is presbycusis (hearing loss due to aging).    But the second most common cause of hearing loss is what audiologists call "noise induced hearing loss (NIHL)."  This type of hearing loss is usually the result of prolonged exposure to loud noises, but it can also result from a singular impulsive sound event such as an explosion or gunfire.  Such hearing loss is also known as acoustic trauma.

Over the course of a lifetime, the human ear is exposed to a multitude of sounds.  These sounds are measured in decibels (dB) (the decibel is a measure of the relationship between two values of power).  To give an idea of the magnitudes under discussion, take this into account:   Normal conversational speech averages between 67dB at normal noise levels.  This is a level at which people can hear and understand easily, without straining.  As sounds increase in intensity (power), or dB, they move into a range where they can damage human hearing.  The average threshold of pain, or great discomfort for the average person is 90dB, or the amount of noise produced by a loud automobile engine.  The Occupational Safety and Health Administration (OSHA), has set standards indicating that 90dB is the level at which sounds begin to be unsafe.  (Any noise over 110dB will cause permanent damage.) Based on these standards, workers who operate in an  environment where the sound threshold is at or above 90dB of noise are not permitted to work longer than eight hours without hearing protection.  As the intensity of the sound increases the amount of time workers are permitted to operate within that environment proportionally decreases.

This relates directly to the dangers of the extreme sound levels produced by  gunfire.  Gunfire produces
impulse noise and contrary to information published in Rolling Stone magazine, impulse noise greater than 110 dB will cause permanent hearing loss.  A standard 2 3/4" 12-gauge shotgun shell produces 156dB of noise when fired, a 158 grain .357 Magnum, 164dB,  and a .22 LR pistol, 152dB.  All of these are significantly above the threshold for pain, and well into the area where damage occurs.  That's the long, drawn out, scientific way of pointing out that wearing the right type of hearing protection is crucial for those who shoot.

Hearing Protection Technology
There are a variety of hearing protection devices available on the market today.  You can choose from soft foam or premolded plastic plugs that are squeezed and inserted into the ear.  You can have custom molded earplugs made.  Or, you can use earmuffs.  While  earplugs and earmolds are helpful and have some advantages, they also have inherent problems and, on average, they don't provide the noise reduction rating (NRR) of earmuffs.  Additionally, they are often ill fitting and can be uncomfortable and cause irritation in the ear canal.  Earmuffs provide a more comfortable, safer, and generally more effective means of hearing protection.  However, standard earmuffs share a defect with plugs and molds.  Specifically, they reduce, or attenuate, sounds across the entire frequency spectrum including conversational speech.  As a result, there are conditions where shooters enhance safety in one sphere (hearing protection) and sacrifice it in another (environmental awareness).  In other words, you've managed to protect your hearing but you can't hear range commands, charging irate mama bears, or the spouse who's calling you for dinner.  The paradox is evident - we want to reduce some sounds and amplify others, all at the same time

There is, however, a technological solution at hand in the form of active, or electronic earmuffs.  The manufacturers of active earmuffs have borrowed technology from the hearing aid industry to develop a product that protects the wearer's hearing, but also allows the wearer to hear conversation.  They do this through the use of something called compression technology.

A brief survey of the history of the hearing aid might prove useful here.  Initially, hearing aids used linear circuitry.  This means a consistent amount of amplification was provided across a wide range of audio input levels.  This proved to be less than completely optimal.  Linear amplification resulted in very uncomfortable and even painful situations for the user when loud noises were further amplified by the hearing aid.  Because of this, peak clipping or limiting circuitry was developed.  With this type of linear amplification, a cutoff level was established, usually at the 90dB level.  When a noise above 90dB came into the circuit, it was automatically clipped, along with every other sound coming in at that moment.  This resulted in very perceptible distortion and poor sound quality, and in most cases the incoming sound shuts off completely.  Conversation was clipped along with the unwanted sound.  This was, again, a suboptimal solution.  As a result, compression amplification was developed in the late 1980's, and came into widespread use in the 1990's.

In compression circuitry, three key parameters control the sound that the wearer perceives.

• The Kneepoint of Compression is the level at which the system begins to compress unwanted sound.
• The Compression Ratio indicates the amount by which the unwanted sound will be compressed.
• The Attack and Release Time, measured in milliseconds, indicates how quickly the sound is compressed and then released to the wearer at the lower level.  The shorter the attack time, the more effectively the user is protected.

Pro-Ears Dimension Earmuffs
Ridgeline, Inc. has developed one of the most advanced hearing protection systems on the market in the Pro-Ears Dimension series.  The design of these muffs overcomes many of the problems that occurred in other muff designs such as ill fitting ear cups and uncomfortable headband pressure.

The Dimension line starts from the ground up to provide the best hearing protection on the market, and this means starting with the muff itself.  In order for earmuffs to be most effective, the earcup must seal off not only the entire ear, but also cover the bony area behind the ear (the mastoid process).  This is needed because sounds can be transferred through the head via a phenomenon known as  bone conduction.  (The skull itself is one of the most effective sound transmitters, and should be covered to maximize hearing protection.)  The ear cups on the Pro-Mag series are large enough to cover both the ear and the mastoid process preventing harmful sounds from being transmitted though the bones.  The Pro-Mag Dimension series was also designed to permit the easy replacement of the sealing rings should they become damaged or cracked.  The headband is thickly padded to reduce pressure on the head.  The muffs alone provide a noise reduction rating of 26 dB.

The tremendous leap taken by the Dimension series is in the sound quality.  The Pro-Mag Dimension series has combined the latest technology in hearing protection with ambient sound amplification.  The kneepoint of these earmuffs are set at 70dB.   As a result, Any sound above 70dB is compressed using a technology known as Dynamic Level Compression (DLC).  This means all sounds in the frequency range above 70dB are compressed equally, resulting in a much more natural sound. The Pro-Mag Dimension series can also boast of the fastest attack time on the market.  The compression circuit of this device reacts in less than 2ms, minimizing the amount of harmful noise getting through is kept to a minimum.  In addition to attenuating loud sounds, amplification is provided across the entire frequency spectrum.  As a result, normal speech  and everyday sounds below the kneepoint are not muffled because you are wearing earmuffs; indeed, the wearer can make these sounds louder at will, up to a maximum 50 dB gain.  Also, since each muff is a separate unit, left and right input can be adjusted individually to compensate for the wearer's needs.

The Dimension series comprises a number of different product lines, each of them optimized for a particular purpose:

• The Pro-Slim, for outdoor shooting (NRR 21)
• The Pro-Mag, for indoor shooting, and shooting magnum or high power firearms (NRR 26)
• The Sporting Clays, for outdoor shotgun games (NRR 20)
• The Stalker, designed to protect hearing while adding enhanced hearing for hunters and outdoorsmen.  Any of the Dimension series can be set up to Stalker standards.

• 2ms reaction time
• Dynamic Level Compression
• 70 dB kneepoint
• 50 dB gain
• Stereophonic sound for true directional sound detection
• Independent volume controls
• 200 hour battery life using standard "N" size batteries
• Entirely made in USA
• Five year warranty

Field Test
That's all very nice, and it makes for interesting and educational reading.  The question that's probably wandering around in your mind, now that you've waded through more information about audio technology that you've ever really wanted to know, is "OK, but does it work?"

We took a pair of Dimension 2 Pro-Mag muffs and subjected them to a series of real world tests, including  pistol and rifle both indoors and outdoors, normal hearing amplification, and a couple of other "true-life" tests we think you'll appreciate.

Comfort
We had three staffers wear conventional muffs for two hours and then switch over to the Dimension muffs for two hours at a stretch.  All told, the reports were positive.  The Dimension muffs were much more comfortable, with far less pinching of the ears than the conventional muffs.  Moreover, the disembodied feeling one gets while wearing muffs due to muffling of outside sounds was absent.  While we wouldn't want to wear any sort of earmuff for extended periods, the Dimension muffs are the best of the breed.   The comfort factor is in itself an added safety factor.  We can't count the number of times we've been on a range when "Cease Fire" has been called, removed our hearing protection, and then had our ears ring for the next two days because someone further away from the range officer didn't hear the command and squeezed off a round from his .575 Nitro-Express-Ackley-Improved-Tympanic-Membrane-Splitter.  With the Dimension muffs, natural sound continues to come in and the muffs are much more comfortable; thus the impulse to tear the muffs off immediately is minimized.  As a result, the wearer continues to be protected from even unanticipated firing noise.

Pistol, Indoor
We used several pistols to test the muffs, to include a Smith&Wesson M57, .41 Magnum, a Tanfoglio "Combat" in .38 Super, and an Argentine Sistema Colt Modelo 1927 in .45 ACP.  Results were similar for all three pistols.  Firing noise was as minimized as with high quality conventional muffs, and at the same time, normal conversation was easily maintained.  In fact the sensation was not unlike having a conversation while being able to hear the sounds of  gunfire at a range one or two hundred yards away.  No interruption in the conversational sound quality was detected.

Pistol, Outdoor
We used the same battery of pistols at an outdoor range.  The results were, if anything, more impressive.  The sound of the firing was almost completely dissipated while at the same time, we were able to hear conversation and the sounds of automobiles moving along a road some seventy five yards away quite clearly.

Rifle, Indoor
Shooting rifles indoors is tough on hearing protection.  Not only are the rifles significantly louder than pistols, but there are a great many surfaces that serve to reflect the sound and the muzzle blast back at the shooter.  We used four rifles to test the muffs, including a Hakim in 7.92mm Mauser, a FAL in 7.62mm NATO, a Tokarev SVT-40 in 7.62x54mmR, and an AK-74 in 5.45x39mm.  These rifles were selected not only because they fire modern high velocity cartridges, but because they all sport effective muzzle brakes that, while reducing recoil and muzzle rise, intensify muzzle blast and the volume of firing sound at or close to the shooter's location.  We used the muffs in both the firing position and while standing next to the shooter.  When firing, the sensation was similar to that experienced when firing the pistols, with the exception that the firing sound was somewhat louder.   Nevertheless, the firing sound never approached a level where it might have been considered uncomfortable, and at the same time, normal conversation was able to continue without any difficulty.  When standing next to the shooter, we had a similar experience, with the exception that the concussion generated by the muzzle blast made us feel the sound, not so much hear it.  Normal conversation was maintained, and the firing sound was effectively muffled, but the pressure wave from the muzzle blast was, well, jarring.  As an aside, the concussive sensations are something that NO earmuff can (or is designed to) minimize.  The best way to avoid them is to stand behind the shooter.

Rifle, Outdoor
As with the pistols, the effectiveness of the muffs increased when we took the rifles outdoors.  The sound of the firing was almost completely dissipated, with ambient sounds and conversation remaining clearly audible and distinct throughout the shooting session.

Ambient Sound Amplification
We had staffers wear the muffs in ordinary (non-shooting) environments to test the muffs' amplification abilities.  The amplification was impressive, to say the least.  We were able to hear high flying aircraft as many as twenty-five seconds prior to those not wearing muffs, crickets and birds inaudible to others, and the sounds of low-toned conversations around corners and in other rooms.

Entertainment
The Dimension 2 muffs we tested have input jacks for radio or personal entertainment electronics.  We wasted no time in assessing this feature.  Listening to Mozart from a Sony Discman or the Rolling Stones from a Walkman, one thing was very evident - the sound quality of the Dimension speakers was outstanding - far better than the headphones that had come with the entertainment devices.  Moreover, there's something sublime about chasing milk jugs about an outdoor range while listening to Beethoven!  As with the ambient noises and conversation, the quality of the music sound suffered not at all while the muffs were filtering firing noises.

Conclusion
At close to $270 retail, the Pro-Mag Dimension 2 series electronic earmuffs are certainly not the least expensive means to protect your hearing while shooting (Note:  The Dimension 1 models are slightly less expensive).  However they are certainly the best, and the most versatile, of the products that we've had the experience to use.  Muffs are more comfortable, and more likely to be used correctly than plugs or molds, and the design of the Dimension muffs makes them more effective at reducing noise than other muffs.  While noise abatement protects the shooter's hearing, the heightened situational awareness provided by the Dimension series' audio electronics protects the shooter and those around him or her.  No other product offers this combination of protection and awareness enhancement.

When one considers that the average collector and shooter may purchase five or ten firearms a year with an average value of $150 - $400, it's hard to justify not spending between two and three hundred dollars on a one time investment that offers a lifetime's worth of hearing protection and safe shooting.  As one of our staffers put it:  "I can always replace a rifle or a pistol.  My eyes and ears are a one shot deal."

We're inclined to agree.  The Pro-Ears Dimension series are an excellent product that should be considered the benchmark for shooter's hearing protection.  For more information on the Pro-Ears product line, please take a look at the Pro-Ears website, http://www.pro-ears.com

CRUFFLER.COM would like to offer sincere thanks and appreciation to audiologist F.M. Mace, M.A., CCC-A, without whose expertise and assistance this review would not have been possible.

And now, our Buy-O-Meter rating for the Pro-Ears Dimension Series Electronic Hearing Protection:
 
 

HOME