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

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

 

Air – What Is It?

Air… We all breathe it, we live in it, we even compress it to use it as a utility.  What is it though?  Well, read through the next to learn some valuable points that aren’t easy to see with your eyes, just like air molecules.

Air – It surrounds us – (Yosuke,1)
  1. Air is mostly a gas.
    • Comprised of roughly 78% Nitrogen and 21% Oxygen.  Air also contains a lot of other gases in minute amounts.  Those gases include carbon dioxide, neon, and hydrogen.
  2. Air is more than just gas.
    • While the vast majority is gas, air also holds lots of microscopic particulate.
    • These range from pollen, soot, dust, salt, and debris.
    • All of these items that are not Nitrogen or Oxygen contribute to pollution.
  3. Not all the Carbon Dioxide in the air is bad.
    • Carbon Dioxide as mentioned above is what humans and most animals exhale when they breathe.  This gas is taken in by plants and vegetation to convert their off gas which is oxygen.
    • Think back to elementary school now.   Remember photosynthesis?
      • If you don’t remember that, maybe you remember Billy Madison, “Chlorophyll, more like Bore-a-fil.”
    • Carbon dioxide is however one of the leading causes of global warming.

      Moisture In The Air – (Grant)2
  4. Air holds water.
    • That’s right, high quality H2O gets suspended within the air molecules causing humidity.  This humidity ultimately reaches a point where the air can simply not hold anymore and it starts to rain.  The lack of humidity in the air leads to static, while lots of moisture in the air when it gets compressed causes moisture in compressed air systems.
  5. Air changes relative to altitude.
    • Air all pushes down on the Earth’s surface.  This is known as atmospheric pressure.
    • The closer you are to sea level the higher the level of pressure because the air molecules are more densely placed.
    • The higher you are from sea level the lower the density of air molecules.  This causes the pressure to be less.  This is also why people say the air is getting a little thin.

Hopefully this helps to better explain what air is and give some insight into the gas that is being compressed by an air compressor and then turned into a working utility within a production environment.  If you would like to discuss how any of these items effects the compressed air quality within a facility please reach out to any Application Engineer at EXAIR.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

1 – Air – Creative Commons – Tsurutea Yosuke – https://www.flickr.com/photos/tsurutayosuke/47732716442/in/photolist-2fHYDBG-dd5e5z-5snidD-oaU8fm-68kqiz-8sMG3P-fnqYx7-9bkTrx-5P2BDv-6R75dG-9vi5xL-5yADR-8EAFci-9NQvER-8sMGoR-4Uybwo-9bNqfB-6N9qf8-6LZyG-7MF4aZ-dehz3-5h1wXk-6uJWNq-7eQCUU-6qoUm6-8sQHxo-uqDdE-6NDHW3-8sQMDQ-7wyCsV-dd5io5-5yAwX-ZmCdh2-BMZCW-agSno-bQ8UFK-6d8Pkz-ars544-novykD-3PF1FT-W13jE9-3GSRLj-7r9Msu-6yn1Ne-32iJKf-7CPqWv-8qhcn-4Eicvh-LLgb4-54ixko

2 – DSC_0750 – Creative Commons – David Grant – https://www.flickr.com/photos/zub/24340293/in/photolist-39Kwe-2cZxjuw-6ywctR-26b7Z2F-84vqJN-bpjRN3-6aDzQR-i84BUr-xbu1Us-fxyvn-5UPDBh-VDz7nD-8Be4fP-a6MVGC-nP4end-PA5nb9-3ddwtq-nRF2yr-j4XPzo-cd5CvJ-eoGFTQ-rYNapy-pKAJpQ-pVrbq6-21hFhHB-n8hpva-7uMwPs-4EZ9ok-jGahK-foR798-JP9rcG-cMRjhu-i74Qo-2d1nE-7nXj3e-9tMib1-6JrXP-9tMdnd-4o5ZCx-6uk2LG-9Gt8K4-5xksdV-9tJgMa-9tMh8b-kkZNy5-c8oM8C-8reqky-4KXe87-aFt7kn-MNNDwU

What Is A NEMA Rating?

With the Summer heat upon us here in Ohio the inquiries for our Cabinet Cooler Systems are increasing by the day.  A question we always ask customers with Cabinet Cooler Sizing Guides is, “What NEMA Type is your enclosure?”  There are quite a few times where no one truly knows what a NEMA rating is. So what exactly is a NEMA rating?

NEMA is the National Electrical Manufacturers Association, one of the many standards they publish is the NEMA rating standard for electrical enclosures up to 1000 Volts.  This standard is where NEMA Types such as 12, 4, and 4X come from (you will also see an international standard reference as “IP”, more on that later).  It categorizes the enclosures by their ability to protect the internal components from things such as corrosion, dust, oil, even external air quality. These standards are reviewed every five years and the last review was done in 2013.  The reviews are generally based on improving safety, clarity of the standard, and testing methods.

So what NEMA ratings does EXAIR offer?  For our Cabinet Cooler Systems, EXAIR offers three very common NEMA types to try an offer a selection to fit the needs that we most commonly encounter.  The NEMA types and their descriptions are below.   For a full list of the Non-hazardous location NEMA enclosure types, click on this link.

EXAIR NEMA 12 Cabinet Cooler System w/ Side Mount Kit

Type 12 (IP54): General purpose, indoor use.  Protects against falling dirt and circulating dust, lint, fibers, and flyings.  Protects against ingress of dripping and splashing water. Rust-resistant Type 12 enclosures do not include knockouts.

 

EXAIR NEMA Type 4 Cabinet Cooler System
EXAIR NEMA Type 4 Cabinet Cooler System

Types 4, 4X (IP66): Water-tight, dust-tight, sleet-resistant.  Resistant to windblown dust.  Indoor or outdoor use.  Also provides protection against splashing and hose-directed water.  The “X” designation indicates corrosion-resistance.

EXAIR's High Temp Cabinet Cooler Systems

The EXAIR Cabinet Cooler Systems also reference an equivalent IEC (International Electrotechnical Commission), IP code.   This is a code from the IEC system which specifies the ingress protection which classifies and rates the degree of protection provided against intrusion (body parts such as hands and fingers), dust, accidental contact, and water by mechanical casings and electrical enclosures. They are a two digit number that represents the level of protection against physical objects and he ingress of water.   Coorelation between NEMA ratings and IP codes is not always possible.  EXAIR has ensured that we also meet the equivalent IP codes shown in the NEMA descriptions above.

If you have a hot enclosure and you are not sure how much cooling is needed or what the NEMA type is, contact us.  We will gladly help you gather the information needed to calculate the heat load requirements and help determine the correct NEMA rating.

Brian Farno
Application Engineer Manager
BrianFarno@EXAIR.com
@EXAIR_BF