Aviation Headset Facts

Aviation Headset Facts

When you are considering the purchase of headsets for use in your aircraft, the first thought that often comes to mind is comfort; however, this is not the most important consideration when buying a headset. Modern piston-powered aircraft and helicopters produce high sound levels, often in the range of 90-95db, and present a major challenge to provide both clear communication and adequate hearing protection.

Noise Reduction Methods:

With respect to noise reduction, the two most popular methods for noise reduction today are Passive Noise Reduction (PNR) and Active Noise Reduction (ANR).

Passive Noise Reduction relies upon clamping the earphone over the ear tightly which is accomplished with large ear muffs and strong clamping pressures.

Active Noise Reduction uses technology which allows the manipulation of sound and signal waves to reduce noise, improve signal-to-noise ratios, and enhance sound quality. The electronic coupling of a low frequency noise wave with its exact mirror image cancels this noise. However, active noise cancellation loses most of its effectiveness where it counts the most – in the speech frequencies of 400 Hz to 4,000 Hz. Active noise reduction really only provides effective protection against low frequency noise.

Options:

Ultimately the choice is yours, whether to reduce noise through covering the ears as thoroughly and tightly as possible, or to rely upon the introduction of more sound frequencies to cancel-out outside noise. I would suggest that before you invest a large amount of money into ANR technology you try it out first – you will probably find that PNR technology, uncomfortable as it may be at first, works best in today’s piston powered aircraft.
Today there are a wide range of aviation headset manufacturers. Among them are PilotUSA, David Clark, Bose, and Avcomm, as well as many more. Whatever your choice you can spend as little as $ 115.00 to over $ 1,000 for an aviation headset and still not be happy. When considering the purchase of an aviation headset make sure the dealer offers you the opportunity to try the headset before you can’t return it. Generally speaking you will be pleased with most of the above mentioned headsets, and they will serve you very well.

For extremely high noise conditions the combination of earplugs with earmuffs or communication headsets is recommended when the ambient noise levels are above 115dB. Earplugs, combined with active noise reduction headsets, provide the maximum level of individual hearing protection that can be achieved with current technology.

Passive headsets cancel sound by blocking sound waves. Sound can be blocked by 3 methods: Barriers, Absorption Material, and Damping Methods. In our aviation headsets, we use the ear cup as walls to enclose the ear and act as an acoustical reflector. The ear cups act as a barrier against the path of noise and eliminates energy of the noise wave. The hard barriers target high frequency noise. We also use different types of acoustical foams to absorb the sound waves and eliminate more energy from the sound waves. Vibration isolators which include spring steel equipment mounts, plastic and rubber based bushings and grommets all contribute to noise canceling by damping the noise. These vibration isolators absorb noise coming in through the headband and ear cup stirrups and also noise waves that are bombarding the ear cups.

Active Noise Reduction, or ANR, reduces noise exposure by introducing sound waves 180 degrees out of phase with the noise, resulting in destructive interference, causing a net reduction of noise at the ear. ANR headsets identify and reduce unwanted noise, allowing improved intelligibility of speech received through the radio and intercom audio and provides better hearing protection.

Aircraft noise has been a longtime problem for pilots when it comes to communicating with one another and protecting themselves from hearing loss. Experts say that persistent noise actually induces added fatigue on pilots. Noise canceling performance is far superior to passive noise protection alone, especially in the lower frequency ranges.

The principle of destructive interference of waves is to generate an inverse pressure wave or "anti-noise" to attenuate unwanted noise. The anti-noise is a sound pressure wave which is the exact opposite of the offending noise: it is the mirror image signal, exact in frequency and amplitude but 180 degrees out of phase or "anti-phase" with the unwanted noise. In order to maximize active noise cancellation, the canceling source always produces with great precision an equal but inverted replica of the signal to be canceled.

The graph below shows the noise and mirror image (Anti-Noise) which is 180 degrees out of phase. The result is noise cancellation.



Summary:

Keep in mind the following factors when evaluating headsets:

• Hearing is second only to vision as a sensory mechanism to obtain critical information during
the operation of an aircraft.
• All sounds have three distinctive variables: frequency, intensity, and duration.
• Normal conversation takes place in the frequency range from 500 to 3,000 Hz.
• Daily exposure to noise levels higher than 90dB can cause hearing impairment. This can go unnoticed initially because it occurs in the vicinity of 4,000 Hz (outside the conversational range)
• If the ambient noise level reaches 90dBA, you must use hearing protection equipment to prevent hearing impairment.
• Exposure to loud noise before flying (at home, while driving, at a party, etc.) can be as harmful as exposure to aircraft noise.

Because headsets are an important purchasing decision, I urge you to consider carefully your choice before committing to something that may not serve the purpose you intend it for. If at all possible, buy from a reliable supplier who will allow you to “test fly” the headset first, and give you the option to return it for a full refund without hassle. Price is certainly important, but not as important as getting the right headset for YOUR situation.

At Aviation Sources we are pleased to provide a 30-day Test Flight, and provide a 100% Money-Back Guarantee with each purchase. Check us out today for Your Pilot Supplies ... Delivered!

Sunglasses for Pilots: Beyond the Image

For most people sunglasses fulfill one, or both, of two purposes: as a fashion statement to look “cool”, and to help cope with bright sunlight. The choices available are seemingly endless, and can range from polarized to photo chromic to colorful tints and shades. But for pilots sunglasses are much more than a fashion statement.

Sunglasses help safeguard a pilot’s most important sensory asset in flight – vision. A quality pair of sunglasses is essential in the
cockpit environment to optimize visual performance. They help reduce the effects of harsh sunlight, decrease eye fatigue, and protect ocular tissue from exposure to harmful solar radiation. Additionally, they protect the pilot’s eyes from impact with objects such as flying debris from a bird strike, sudden decompression or an aerobatic maneuver.

TINTS

The choice of tints for sunglasses is almost infinite, but the three most common tints are gray, gray-green, and brown, any of which would be an excellent choice for the aviator. Gray is recommended the most because it distorts color the least. Many pilots, however, report that gray-green and brown tints enhance vividness and minimize scattered blue and violet light, thus enhancing contrast in hazy conditions.

LENSES

For a pilot, sunglass lenses should screen out only 70-85% of visible light and not appreciably distort color. Any tints that block out more than 85% of visible light are not recommended for pilots due to the possibility of reduced visual acuity which could result in difficulty seeing the flight instruments, written checklists and data inside the cockpit.

While polarized lenses are very popular, they are not recommended for use in the aviation environment. While they are useful for blocking reflected light from horizontal surfaces such as water or snow, polarization can reduce or eliminate the visibility of flight instruments that incorporate anti-glare filters like the new glass cockpit environments. These polarized lenses may also interfere with visibility through an aircraft windscreen by enhancing striations in laminated glass and mask the sparkle of light reflected off of another aircraft’s fuselage or wings, which in turn can reduce the ability of pilots to “see-and-avoid” other aircraft.

Photo chromic lenses automatically darken when exposed to ultraviolet light and become lighter in dim light. The majority of the darkening takes place within 60 seconds, while lightening may take several minutes. While most photo chromic lenses can get as dark as regular sunglasses, direct sunlight or warm temperatures above 70 degrees Fahrenheit can seriously limit their ability to darken, and reduced ultraviolet light exposure in a cockpit can further limit their effectiveness. Further, the faded state of photo chromic lenses may not be clear enough to be useful when flying in clouds or at night.

FRAMES

The selection of frames is more a matter of personal preference; however, bayonet style temples are the most popular because they are easy to put on or remove while wearing headsets or a helmet. Smaller lenses may not be practical because they allow too much visible light and ultraviolet radiation to pass around the edges of the lenses. Finally, use of a strap is recommended to prevent the sunglasses from being accidentally dislodged.

SUMMARY

In summary, while sunglasses may add to the mystique of a pilot, sunglasses are the most important method to protect the pilot’s eyes from glare associated with bright sunlight and the effects from exposure to solar radiation. Since sunglasses are such an important asset, careful consideration should be used when selecting an appropriate pair for flying.

Since 1982, Randolph Engineering has been standard issue for U.S. military pilots. Not only are their sunglasses made in the USA, but quality of materials and the precision of manufacturing the Randolph Aviator, their flagship product, actually surpass the exacting standards of the military. So when NASA Astronauts lift off the launch pad and head for outer space, Randolph is right there with them. When America's Top Gun Pilots step into the cockpit of a sleek jet fighter or the magnificent Stealth Bomber, Randolph is the priceless pair of sunglasses that helps those pilots safely navigate the skies.

To find the internet’s best selection of Randolph Engineering sunglasses see:

Randolph Sunglasses at Aviation Sources .

Blogarama