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Measurements are commonly displayed as dB(A) or dBA or as LAeq, LAFmax, LAE.Ĭ-weighting – (C-frequency-weighting). Any approved sound level meter meeting IEC 61672 is mandated to incorporate at least an A-weighting filter. The ‘A’ weighting adjusts the sound pressure level readings to reflect the sensitivity of the human ear and is therefore mandated all over the world for hearing damage risk measurements. The human ear is most sensitive to sound frequencies between 500 Hz and 6 kHz (especially around 4 kHz) whilst at lower and higher frequencies the human ear is not very sensitive. ‘A’ Weighted is the most commonly used and covers the full frequency range of 20Hz all the way up to high frequency 20 kHz. It is defined in various international standards such as the IEC 61672, as well as in various national standards such as ANSI S1.4. A sound level meter weighting that makes its readings conform to a notional human hearing response. What are ‘A’, ‘C’ and ‘Z’ weightingsĪ-weighting – (A-frequency-weighting). The three most commonly used decibel weightings are ‘A’, ‘C’ and ‘Z’ as defined in the sound level meter standards IEC 61672:2013 (BS EN 61672-1:2013), but which one do you choose? We explain this is more detail below, but if you own one of our Pulsar Nova sound level meters which measures all of these frequencies simultaneously, you need not ever worry about picking the wrong weighting. You may have noticed that some sound meters allow you to choose the frequency weighting you want to measure noise at. This is because picking the wrong sound level meter weighting on your sound level pressure meter could mean your results become irrelevant for the purpose and at worst invalid (not legally compliant). Understanding A-C-Z noise frequency weightings ad the differences between them is one of the most important things you need to know about when measuring sound. If you need to raise your voice to be heard at an arm’s length, the noise level in the environment is likely above 85 dB in sound intensity and could damage your hearing over time.What are the different frequency weightings and why do you need to know? The risk of damaging your hearing from noise increases with the sound intensity, not the loudness of the sound. For example, ten violins would sound only twice as loud as one violin. In general, to measure loudness, a sound must be increased by 10 dB to be perceived as twice as loud. A sound that seems loud in a quiet room might not be noticeable when you are on a street corner with heavy traffic, even though the sound intensity is the same. Loudness refers to how you perceive audible sounds. Two sounds that have equal intensity are not necessarily equally loud. Also, the intensity of a sound at 100 dB is one billion times more powerful compared to a sound at 10 dB. This means that a sound at 20 dB is 10 times more intense than a sound at 10 dB. Instead, the intensity of a sound grows very fast. The decibel scale is logarithmic, which means that loudness is not directly proportional to sound intensity. Sound intensity is the amount of sound energy in a confined space. How loud something sounds to you is not the same as the actual intensity of that sound.
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For more information, visit NIOSH’s website. The time estimates listed in the “Typical Response” column are based on the NIOSH exchange rate of 3 dB. Hearing loss possible in less than 2 minutes Hearing loss possible in less than 5 minutes The maximum volume level for personal listening devices a very loud radio, stereo, or television and loud entertainment venues (such as nightclubs, bars, and rock concerts) Sounds at these dB levels typically don’t cause any hearing damage.ĭamage to hearing possible after 2 hours of exposureĭamage to hearing possible after about 50 minutes of exposureĪpproaching subway train, car horn at 16 feet (5 meters), and sporting events (such as hockey playoffs and football games) Typical Response (after routine or repeated exposure) Sounds and Noises Everyday Sounds and NoisesĪverage Sound Level (measured in decibels)