Measuring And Adding Sound Levels Together

What sound level do you get when you feed an EXAIR Super Air Nozzle at 80psig? What if there are two of them?  Or three?  Grab your scientific calculators, folks…we’re gonna ‘math’ today!

But first, a little explanation of sound power & sound pressure:

Strictly speaking, power is defined as energy per unit time, and is used to measure energy generation or consumption.  In acoustics, though, sound power is applicable to the generation of the sound…how much sound is being MADE by a noisy operation.

Sound pressure is the way acoustics professionals quantify the intensity of the sound power at the target.  For the purposes of most noise reduction discussions, the target is “your ears.”

The sound levels that we publish are measured at a distance of 3 feet from the product, to the side.  The units we use are decibels, corrected for “A” weighting (which accounts for how the human ear perceives the intensity of the sound, which varies for different frequencies,) or dBA.  Also, decibels follow a logarithmic scale, which means two important things:

  • A few decibels’ worth of change result in a “twice as loud” perception to your ears.
  • Adding sources of sound doesn’t double the decibel level.

If you want to know how the sound level from a single source is calculated, those calculations are found here.  For the purposes of this blog, though, we’re going to assume a user wants to know what the resultant sound level is going to be if they add a sound generating device to their current (known) situation.

Combined Sound Level (dBA) = 10 x log10[10SL1/10 + 10SL2/10 + 10SL3/10 …]

Let’s use an EXAIR Model 1100 Super Air Nozzle (rated at 74dBA) as an example, and let’s say we have one in operation, and want to add another.  What will be the increase in dBA?

10 x log10[1074/10 + 1074/10] = 77.65 dBA

Now, there are two reasons I picked the Model 1100 as an example:

  • It’s one of our most versatile products, with a wide range of applications, and a proven track record of efficiency, safety, and sound level reduction.
  • We proved out the math in a real live experiment:

Why do I care about all of this?  My Dad experienced dramatic hearing loss from industrial exposure at a relatively young age…he got his first hearing aids in his early 40’s…so I saw, literally up close and very personal, what a quality of life issue that can be.  The fact that I get to use my technical aptitude to help others lower industrial noise exposure is more than just making a living.  It’s something I’m passionate about.  If you want to talk about sound level reduction in regard to your use of compressed air, talk to me.  Please.

Russ Bowman
Application Engineer
EXAIR Corporation
Visit us on the Web
Follow me on Twitter
Like us on Facebook

Reduce Sound Level in your Factory, Improve Worker Safety and Comfort

Checking the sound level in your processes is an important aspect of ensuring a safe working environment for your employees. Loud noises and the exposure time can lead to significant health concerns. Permanent hearing loss, increased stress levels due to the uncomfortable work environment, and potential injury due to lack of concentration or inability to hear the surroundings are all examples of some risks associated with a noisy environment.

The Occupational Safety and Health Administration, known by most simply as OSHA, introduced Standard 29 CFR 1910.95(a) as a means of protecting operators from injury associated with high noise levels. The chart below indicates maximum allowable exposure time based on different noise levels. At just 90 dBA, an operator can operate safely for 8 hours. Open end pipe blowoffs and some air guns fitted with cross drilled relief holes will often result in noise levels in excess of 100 dBA. At 110 dBA, permanent hearing loss can be experienced in just 30 minutes!

OSHA Chart

The first step to lowering your sound level is to take a baseline reading of your various processes and devices that are causing the noise. EXAIR’s Sound Level Meter, Model 9104, is an easy to use instrument that provides a digital readout of the sound level. They come with an NIST traceable calibration certificate and will allow you to determine what processes and areas are causing the most trouble.

SoundMeter_new_nist225

From there, EXAIR has a wide range of Intelligent Compressed Air Products® that are designed to reduce compressed air consumption as well as sound levels. For noisy blowoffs where you’re currently using an open-ended pipe or a loud cross-drilled nozzle, EXAIR’s Super Air Nozzles are the ideal solution. Not only will they pay for themselves over time due to compressed air savings, but your operators will thank you when they’re able to hear later on in life!!

Drilled pipe is another common culprit of high noise levels. Rather than purchasing an engineered solution, the idea is that a simple drilled pipe is just as effective right? Not at all!! Not only does a drilled pipe produce exceptionally high sound levels, but the amount of compressed air used is also very inefficient. EXAIR’s Super Air Knife is available in lengths ranging from 3”-108” and has a sound level of just 69 dBA at 80 PSIG. At this sound level, operators won’t even require hearing protection at all!

SAK vs drilled pipe
EXAIR’s Super Air Knife is the ideal solution for replacing noisy, inefficient drilled pipe

With all of these products available in stock, EXAIR has the tools you need to reduce sound level in your processes. If you’d like to talk to an Application Engineer about any applications that you feel could benefit from a sound reduction, give us a call.

Tyler Daniel
Application Engineer
E-mail: TylerDaniel@EXAIR.com
Twitter: @EXAIR_TD