"A" Weighting - Typically used in both industrial and community noise applications. "A" weighted measurements are reported in dBA. This scale corresponds to the way the human ear hears across the speech frequencies.

"C" Weighting - Provides a flat frequency response with slight attenuation of the very high and very low frequencies. "C" weighted measurements are reported in dBC.

CE - The CE mark is a symbol of conformity on industrial safety products that have been approved for sale in the European Union (EU). CE conformity indicates that the safety product and systems within the manufacturer's company satisfactorily meet, or exceed, the established requirements of quality assurance, user information and on-going testing. Effective July 1, 1995, all safety products sold into the EU must be tested, approved and carry the CE mark.

Continuous Noise - The intervals of the sound waves are less than on second apart.

Decibel - A logarithmic unit of measure often used as the scale for sound pressure levels (SPL). This is perceived as "loudness or intensity".

Exchange Rate - The rate in which sound energy is averaged over time. Utilizing a decibel scale, every time the sound energy doubles, the measured level increases by 3 dB. This is the 3 dB exchange rate that most of the world uses.

External Ear - Consists of the Pinna or the visible portion of the ear and the external auditory canal.

Frequency - Represents the number of cycles of vibration that occur in one second. The number of cycles is designated in Hertz (Hz). This is perceived as "pitch".

Impulsive Noise - The intervals of the sound waves are greater than one second apart and are characterized by a high-amplitude, very short wave.

Inner Ear - Cochlea, semicircular canals and auditory nerve.

Mean Attenuation - The average attenuation value calculated received in each test frequency.

Middle Ear - Includes ear drum and ossicular chain (malleus, incus and stapes).

NIHL - Noise Induced Hearing Loss due to noise exposure.

NRR/Noise Reduction Rating- NRR, or Noise Reduction Rating is a rating system set up by the Environmental Protection Agency (EPA) as a guideline that indicates the amount of potential protection a hearing protection device will give in a noisy environment. All Howard Leight hearing protection devices are tested under the Real Ear Method as directed by the American National Standard Institute (ANSI) in accordance with test procedures established by the Acoustical Society of America. All testing is performed in a controlled environment. Consequently, posted NRR ratings are a qualified example of how the individual products compare with other similar hearing protection products in an uncontrolled noise environment. Test results do not evaluate the product reusability, comfort, adaptability or quality. In the final analysis, the user must make this determination.

Pinna - The visible, outer portion of the ear, which should be enclosed completely by ear muff cups.

Presbycusis - Type of sensory neural hearing loss due to aging.

PTS - Permanent Threshold Shift refers to a permanent change in hearing thresholds due to noise exposure.

SLC80 - The Australian standard for testing hearing protection products.

Sound Level Meter - An instrument for the measurement of sound level. It consists of a microphone, a frequency selective amplifier and an indicator. It measures sound level in dB SPL.

SNR - Single Number Rating is a rating system set up by the European Union (EU). Tests are conducted by independent testing laboratories with no direct participation by manufacturers. The independent testing laboratories meet all of the regulatory requirements as set out by the EU. The test results serve as a guideline to indicate the amount of potential protection a hearing protection device will give in a noisy environment. All Howard Leight hearing protection devices are tested according to the requirements established under EN 352.2 1993 (ear plugs) and EN 352.1 1993 (ear muffs). All tests are performed ant independent testing laboratories located at either B.I.A., Germany, or by Inspec Laboratories LTD, England at the University of Salford, Department of Acoustics.

Tinnitus - Presence of ringing, buzzing or humming in the ear which can be intermittent or continuous.

TTS - Temporary Threshold Shift refers to a temporary change in hearing thresholds due to noise exposure.