How to read this information:
Any manufactured product has some variation between units normally. The
same holds true with ear plugs. So rather than saying all earplugs will
produce the exact same noise reduction, the testing standards for
reporting require that two numbers are reported for each frequency: the
typical (MEAN) amount of noise reduction for any given pair out of the
manufacturing process, and the range of variation that can be expected
from that number (STANDARD DEVIATION).
About 68% of all units will be within 1 standard deviation of the mean; 94% will be within
two standard deviations of the mean.
Thus, if the data says that at 4000Hz the ear plug has a mean of 41.9dB and a standard deviation of 5.1dB,
then 68% of all the ear plugs of that type will block between
36.8dB and 47.0dB at 4000 Hz, and 94% will block between 31.7dB and 52.1dB at that frequency.
Follow this link to help you understand Standard
Deviation, if you still need a better explanation.
To understand the frequency ranges, human voices usually occur in the band from 800 Hz to 4000 Hz, with an exceptionally deep male voice usually being around 600 to 1000 Hz and a very high pitched female scream can be as high as 3400 to 4000 Hz. A normal telephone's audio range is normally 300Hz to 3400Hz.
| FREQUENCY (in Hz) |
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| ←← Mostly Exhaust Noises | BOTH | Mostly Wind Noise →→ | |||||||
| MEAN dB CUT | |||||||||
| STANDARD DEVIATION |
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| FREQUENCY (in Hz) |
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| ←← Mostly Exhaust Noises | BOTH | Mostly Wind Noise →→ | |||||||
| MEAN dB CUT | |||||||||
| STANDARD DEVIATION |
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| FREQUENCY (in Hz) |
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| ←← Mostly Exhaust Noises | BOTH | Mostly Wind Noise →→ | |||||||
| MEAN dB CUT | |||||||||
| STANDARD DEVIATION |
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Copyright 2004, all rights reserved. Material on this page may not be used or reused without express written permission from the copyright holder. For information on licensing, contact the webmaster. Marc Glasgow is a Macintosh "Mac" Consultant serving the Tampa Bay area since 1990. |