The word noise means any unwanted sound. In electronics, signal noise is a disturbance to a wanted signal. You experience this as ‘snow’ (pixelation) on a television or video image. In fiberoptics it’s the contravention of light. In audible (acoustical) sound it is excessive, displeasing tones. We live in a noisy world. On a daily basis we are being assaulted with sounds from cars, planes, and yes those subwoofers from the neighbor kid’s car stereo that knocks the glazing out of your windows.
Sound is sequence of oscillating pressure waves that propagate through a compressible media such as air or water Sound cannot travel through a vacuum. It is measured by the deviation of pressure on a logarithmic scale and calculated by the root mean square of the instantaneous sound pressure over a given interval of time and is expressed in decibel (dB). The scale starts at zero which is the lowest level of sound that a person can hear. Being logarithmic for every 3 dB reduction cuts sound energy in half, 10 dB reduction decreases sound energy by a factor of 10, and 20 dB reduction decreases sound energy by a factor of 100
Normal speaking voices are around 65 dBA. A rock concert can be about 120 dBA ( 120 dB is considered the human threshold for pain), and eardrum rupture can occur at 150 dB
These pressure variations cause our ear drums to vibrate and we interpret them as sound. The ear drum is a thin, sensitive membrane that can be easily damaged to extended exposure to high levels of sound. Studies have shown sustained exposure to high levels of noise can cause stress, hypertension, and even cardiovascular problems.
The Occupational and Health Authority has set the length of exposure for various sound levels (OSHA 29 CFR 1910.95(a) and is stated below.
TABLE G-16 – PERMISSIBLE NOISE EXPOSURES (1)
|hours per day||dBA|
|1/4 or less||115|
To keep your workplace in compliance a simple audit with a sound level meter is all that is needed.
EXAIR’s Model 9104 Digital Sound Level Meter measures and displays sound pressure levels in dB from 35 to 130dB. The LCD is backlit for viewing readings in dimly lit areas. User selectable features include Frequency Weighting (‘A’ and ‘C’), Response Time (Fast and Slow), Max Hold, and Range (High and Low).
Need some assistance? Call 1-800-903-9247 and ask to speak with one of our application engineers.