Sound levels are an important safety consideration in most industrial facilities. OSHA has guidelines on allowable noise levels and exposure, covered in OSHA Standard 29CFR – 1910.95 (a). Sound levels are measured in decibels, or dB. It makes sense that a higher decibel value means a louder sound (as illustrated in the graphic below). What is not intuitive is how multiple sound levels interact and combine, or how they compare to one another.
The first thing to understand about sound levels is that they aren’t measured on a linear scale. Instead, they’re measured on a logarithmic scale. This can really throw off our intuition. For instance, a sound at 20dB is actually 10 times stronger than one at 10dB, and a sound at 30dB is 100 times stronger than 10dB. If it were a linear scale, 20dB and 30dB would only be 2 and 3 times stronger than 10dB, similar to how mass works—like 20kg being double the mass of 10kg.
You can see why this is the case with the formula for calculating sound levels, which is as follows:
It’s important to note that the sound pressure levels calculated using this formula are unweighted. To really grasp how loud something will seem to us, we have to consider how our ears pick up various frequencies. This means that low and extremely high frequencies are given less weight than on the standard decibel scale. This adjusted measurement is referred to as dBA. You can check out some typical sounds and their dBA levels in the chart below:
Because of this logarithmic scale, combining two sounds can be pretty counter-intuitive too. Our Model 1100 Super Air Nozzle generates a sound level of 74 dBA, but when you place two of them side by side, the sound level jumps to 78 dBA (and not 148dBA). This is determined using the formula below:
The specifics of this calculation are explained in this blog here, but OHSA provides a quick and easy way to calculate, as shown in the table below:
To see if you need to tackle the noise levels in your facility, you should start by taking a baseline measurement of the different processes and devices that are making the noise. EXAIR’s Sound Level Meter, Model 9104, is here to help. It’s super user-friendly and gives you a digital readout of the sound level (no need to deal with logarithms!).
If you would like to discuss sound levels in your facility, or any of your other compressed air needs, give us a call!
Al Wooffitt
Application Engineer
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