Tag: dB

EXAIR Product Overview: Mufflers

Published on by codybiehleLeave a comment

Noise, we all hate it to some extent. From the hustle and bustle of crowed streets to the whine of a jet engine noise has plagued the world for eons leaving people to search for a way to escape into a moment of peace and quiet. The majority of people that I know pack their massive over sized backpacks and head deep into the mountains for days on end to escape the noise sometimes traveling for 10+ miles at a time. But how can we help eliminate this monstrosity that we have created in our manufacturing environments? The answer is mufflers, and no I don’t mean your car muffler (although they do the same thing) I mean compressed air mufflers. Compressed air can be a loud utility inside of a plant environment and exceed the OSHA guidelines for personnel noise exposure. But this noise can easily be mitigated with the use of Intelligent compressed air products and mufflers.

Big Sandy Lake Trail – Wind River Range State Park, WY

OSHA Standard 29 CFR 1910.95(a) outlines the total noise exposure to a particular noise level per day and dictates that noise exposure at or above 85 decibels require ear protection. By placing a muffler on the end of the pipe one can reduce the sound level significantly to the point it could be the difference between having to wear ear protection and not having to. With that being said EXAIR offers four different types of mufflers to choose from and they are Reclassifying, Sintered Bronze, Straight-Through, and Heavy Duty.

Reclassifying mufflers offer the best noise reduction at 35 dB and have the added benefit of removing oil mist from the air line. This means that the Reclassifying mufflers are ideal for pneumatic cylinders. Per OSHA Standard 29 CFR 1910.1000 worker shall not be exposed to more than 5mg/m3 of oil by volume in a 40-hour work week. The patented design of the removable element separates oil from the exhausted air and meets or exceeds the OSHA Standard.

The quick pick chart for easily choosing which muffler you need

Sintered Bronze Mufflers are an excellent low-cost solution which can be easily installed into your current existing ports. These mufflers also come in the largest variety of different sizes ranging from thread sizes of #10-32 to 1.5” NPT. Also, the Sintered Bronze Mufflers are specifically designed to provide the minimal amount of back pressure and restriction. The main difference between these mufflers and the reclassifying is that the Sintered Bronze Mufflers cannot collect oil out of the exhaust.

The quick pick chart for easily choosing which muffler you need

If the process air needs to be directly plumbed away from personnel, then the Straight-Through Muffler is the way to go. Straight-Through Mufflers are ideal for situations that require both a threaded inlet and exhaust. In most applications you will see the Straight-Through Muffler pair with our E-Vac vacuum generators or Vortex Tubes to provide noise reduction of the unit. All in all, the Straight-Through Muffler can reduce noise levels up to 20 dB.

Model 3913 Straight-Through Muffler

Lastly, the Heavy Duty Muffler provides a corrosion resistant aluminum outer shell with a stainless steel inner screen. This design allows the muffler to catch any contaminants such as rust from being ejected potentially causing harm or quality defects. Typically, this muffle will reduce noise levels up to 14 dB.

Model 3903 Heavy Duty Muffler

If you have any questions or want more information on EXAIR’s E-Vacs and their Accessories. Give us a call, we have a team of application engineers ready to answer your questions and recommend a solution for your applications.

Cody Biehle
Application Engineer
EXAIR Corporation
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Understanding Noise: Sound Power Vs. Sound Pressure

Published on by Jordan T ShouseLeave a comment
Sound Power and Sound Pressure have been covered a few other times here on the EXAIR Blog. Once here by Brian who made the visual correlation in regards to a speaker and a musical instrument. And here by Russ who breaks down how you calculate sound power level with the below equation!
Sound Power Equation
too lou Sound Power Level Equation
All machines generate sound when they are in operation. The propagated sound waves cause small changes in the ambient air pressure while traveling. A sound source produces sound power and this generates a sound pressure fluctuation in the air. Sound power is the cause of this, whereas sound pressure is the effect. To put it more simply, what we hear is sound pressure, but this sound pressure is caused by the sound power of the emitting sound source. To make a comparison, imagine for example a simple light bulb. The bulb’s power wattage (in W) represents the sound power, whereas the bulb’s light intensity represents the sound pressure.
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Light Bulb
Sound power does not generally depend on the environment. On the contrary, the sound pressure depends on the distance from the source and also on the acoustic environment where the sound wave is produced. In the case of indoor installations for example, sound pressure depends on the size of the room and on the sound absorption capacity of the surfaces. For instance, say the room walls don’t absorb all the sound but reflect parts of it, then the sound pressure will increase due to the so called reverberation effect. (reverberation time is broadly defined as the time it takes for the sound pressure to reduce by 60 dB after the sound emitting source has been shut off). OSHA puts the following limits on personnel exposure to certain noise levels:
Working in areas that exceed these levels will require hearing protection.
EXAIR’s line of Intelligent Compressed Air Products are engineered, designed, and manufactured with efficiency, safety, and noise reduction in mind.  If you’d like to talk about how we can help protect you and your folks’ hearing, call us. Jordan Shouse Application Engineer Send me an email Find us on the Web  Like us on Facebook Twitter: @EXAIR_JS Light Bulb image courtesy of  josh LightWork  Creative Commons License

Measuring And Adding Sound Levels Together

Published on by Russ BowmanLeave a comment

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
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Sound: What Is It … More Importantly, Weighted Scales of Frequencies

Published on by Brian FarnoLeave a comment

We’ve blogged about sound and what exactly it is before, see the link. Understanding that sound is vibration traveling through the air which it is utilizing as an elastic medium.  Well, rather than me continue to write this out, I found a great video to share that is written in song to better recap how sound is created.

Now that we have that recap and understand better what sound is let’s dig a little deeper to better understand why some sounds may appear louder to a person when they may not appear different on a sound scale that is shown by something like a Digital Sound Level Meter.

Loudness is how a person perceives sound and this is correlated to the sound pressure of the frequency of the sound in question.  The loudness is broken into three different weighing scales that are internationally standardized. Each of these scales, A, C, and Z apply a weight to different frequency levels.

  1. The most commonly observed scale here in the USA is the A scale. A is the OSHA selected scale for industrial environments and discriminates against low frequencies greatly.
  2. Z is the zero weighting scale to keep all frequencies equal, this scale was introduced in 2003 as the international standard.
  3. C scale does not attenuate these lower frequencies as they are carrying the ability to cause vibrations within structures or buildings and carry their own set of risks.

To further the explanation on the A-weighted scale, the range of frequencies correlates to the common human hearing spectrum which is 20 Hz to 20kHz. This is the range of frequencies that are most harmful to a person’s hearing and thus were adopted by OSHA. The OSHA standard, 29 CFR 191.95(a), that corresponds to noise level exposure permissible can be read about here on our blog as well.

When using a handy tool such as the Digital Sound Level Meter to measure sound levels you will select whether to use the dBA or dBC scale.  This is the decibel reading according to the scale selected. Again, for here in the USA you would want to focus your measurements on the dBA scale. It is suggested to use this tool at a 3′ distance or at the known distance an operator’s ears would be from the noise generation point.

Many of EXAIR’s engineered compressed air products have the ability to decrease sound levels in your plant. If you would like to discuss how to best reduce sound levels being produced within your facility, please contact us.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

 

1 – Fun Science: Sound – @charlieissocoollike – https://youtu.be/xH8mT2IQz7Y