Sound Power Level and Sound Pressure

Energy…all day (and night) long, we humans are surrounded by – and bombarded by – all kinds of energy. Sometimes, the effects are pleasant; even beneficial: the warmth of the sun’s rays (solar energy) on a nice spring day is the sure-fire cure for Seasonal Affective Disorder, and is also the catalyst your body needs to produce vitamin D. Good things, both. And great reasons to get outside a little more often.

Sometimes, the effects aren’t so pleasant, and they can even be harmful. Lengthy, unprotected exposure to that same wonderful sun’s rays will give you a nasty sunburn. Which can lead to skin cancer. Not good things, either. And great reasons to regularly apply sunblock, and/or limit exposure if you can.

Sound is another constant source of energy that we’re exposed to, and one we can’t simply escape by going inside. Especially if “inside” is a factory, machine shop, or a concert arena. This brings me to the first point of today’s blog: sound power.

Strictly speaking, power is energy per unit time, and can be applied to energy generation (like how much HP an engine generates as it runs) or energy consumption (like how much HP a motor uses as it turns its shaft) For discussions of sound, though, sound power level is applied to the generation end. This is what we mean when we talk about how much sound is made by a punch press, a machine tool, or a rock band’s sound system.

Sound pressure, in contrast, is a measure of the sound power’s intensity at the target’s (e.g., your ear’s) distance from the source. The farther away you get from the sound’s generation, the lower the sound pressure will be. But the sound power didn’t change.

Just like the power made by an engine and used by a motor are both defined in the same units – usually horsepower or watts – sound power level (e.g. generation) and sound pressure (e.g. “use” by your ears) use the same unit of measure: the decibel.  The big difference, though, is that while power levels of machinery in motion are linear in scale, sound power level and pressure scales are logarithmic.  And that’s where the math can get kind of challenging.  But if you’re up for it, let’s look at how you calculate sound power level:

Sound Power Level Equation


Wis reference power (in Watts,) normally considered to be 10-12 W, which is the lowest sound perceptible to the human ear under ideal conditions, and

W is the published sound power of the device (in Watts.)

That’s going to give you the sound power level, in decibels, being generated by the sound source.  To calculate the sound pressure level:

Sound Power Level to Sound Pressure Equation


Lis the sound power level…see above, and

A is the surface area at a given distance.  If the sound is emitted equally in all directions, we can use the formula for hemispheric area, 2πrwhere r=distance from source to calculate the area.

These formulas ignore any effects from the acoustic qualities of the space in which the sound is occurring.  Many factors will affect this, such as how much sound energy the walls and ceiling will absorb or reflect.  This is determined by the material(s) of construction, the height of the ceiling, etc.

These formulas may help you get a “big picture” idea of the sound levels you might expect in applications where the input data is available.  Aside from that, they certainly put into perspective the importance of hearing protection when an analysis reveals higher levels.  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.


Dollar Savings: Open Pipes vs EXAIR Air Nozzle

Early one morning we received a call from a local metal stamping company that had a problem. They had outstripped the volumetric capacity of their (2) 50 HP air compressors.

They were using open copper tubes to facilitate separating the part from the die on the upstroke and then blow the part backwards into the collection chute. The (5) 1/4” copper tubes were all connected to a single manifold with a valve to control each tube.  Compounding their compressed air shortage was that this setup was duplicated on approximately (8) presses.  Per the plant they run the presses for approximately (4) hours per day.  The volume of air required for one press was calculated as:

One 1/4” open copper pipe consumes 33 SCFM @ 80 PSIG, therefore:


Due to the award winning design of EXAIR’s engineered air nozzles the plant achieved faster separation of the part from the die and greater efficiency moving the part to the collection chute, while averting the need to purchase a larger air compressor. They are saving air, reducing energy costs and lowering the noise level in their facility.

If you would like to discuss saving air and/or reducing noise, I would enjoy hearing from you…give me a call.

Steve Harrison
Application Engineer
Send me an email
Find us on the Web 
Follow me on Twitter
Like us on Facebook



EXAIR’s Flat Nozzles: Safe, Reliable, and Efficient

Here on the EXAIR Blog we frequently discuss dead-end pressure as explained in OSHA Standard 1910.242(b). This directive states that the when compressed air is used for cleaning purposes, the dead-ended pressure must not exceed 30 psig. When pressures greater than this occur, there is potential for an air embolism. This animation shows and explains how an air embolism can affect the body.

EXAIR’s Flat Nozzles adhere to this OSHA directive. The Flat Nozzles consist of three primary components: the body, the cap, and the shim. The thickness of the shim will dictate the flow and force through the nozzle and can be easily adjusted. The cap slightly protrudes from the body and shim, creating a gap when it is pressed up onto the skin. By ensuring that there is always an avenue for that air to escape, there is no potential for it to be dead-ended.

From top to bottom: Model 1126, 1126SS, 1122, and 1122SS

EXAIR’s flat nozzles are available in two sizes: 1” and 2”. Each size has a shim set that can be purchased for adjusting both the flow and force from the nozzle. These nozzles are available in both zinc/aluminum alloy as well as 316 grade Stainless Steel. They can be used by themselves, installed on our Safety Air Guns, or in conjunction with our Stay Set Hoses that allow for easy re-positioning.

You may have seen (or used) the plastic flat nozzles that come in a variety of different colors. EXAIR’s flat nozzle is a safe, efficient, and more robust replacement that will maintain a similar airflow pattern at a dramatically reduced operating cost. Where plastic nozzles may become damaged or break off, the rigid construction of EXAIR’s Flat Nozzle will not. In addition to be safe, durable, and reliable, EXAIR’s flat nozzles also offer a reduced sound level compared to these styles of nozzle. Reducing sound is another directive that OSHA 29 CFR 1910.95 covers. If you’re using an unsafe nozzle in your facility, OSHA can quickly begin assessing fines for each violation. They don’t announce their visits beforehand, so make sure you do your due diligence and assess your compressed air blowoff products yourself!

EXAIR 2″ Flat Super Air Nozzle “blows” away the competition!

If you would like to discuss how to make your compressed air use safer and more efficient, give us a call. Our team of highly-trained Application Engineers is standing by, ready to help you make the switch to an Intelligent Compressed Air Product.

Tyler Daniel
Application Engineer

Super Air Knife Makes EVERYTHING Better

When we compare the EXAIR Super Air Knife to other methods of providing a curtain or sheet of air flow in terms of operating cost, efficiency, safety, and sound levels, the Super Air Knife is ALWAYS the clear choice.

The EXAIR Super Air Knife is the most efficient and quietest compressed air blow off product on the market today.

The Super Air Knives successfully replace these, and many other methods of providing a curtain or sheet of air flow all the time, while saving compressed air and decreasing noise.  The word “replace” oftentimes means “do the same job as.”

What you’re about to read is NOT one of those times.

A paper products manufacturer has a machine that treats a specialty product, and the process generates ozone (O3) at levels that would exceed personnel exposure limits, so they need to be contained.  They installed a long piece of drilled pipe to blow an air barrier, but they could only run the machine at about 65% of their desired capacity before the ozone level in the operators’ area exceeded their limits.

This company was familiar with several of our product lines already…they had several Cabinet Cooler Systems, a Reversible Drum Vac, and Super Air Knives in a variety of applications, so they knew how they worked.  Since the barrier needed to be 120″ long, though, this was going to be a much larger scale than they were used to.

Not only was the drilled pipe loud and inefficient, it was not particularly effective either.

Still, the installation of two Model 110060 60″ Aluminum Super Air Knives, coupled with our Model 110900 Air Knife Coupling Kit, was quick and easy.  Then came the good part: they found they were able to operate the machine at 100% capacity, while keeping the ozone at a safe level in the operators’ area.

EXAIR Super Air Knives provided a total solution: quiet, efficient, and most of all, EFFECTIVE.

Then came the better part:  The machine was pretty loud (we couldn’t do anything about that,) at 93dBA when it was running.  With the drilled pipe in operation, it was 94.5dBA.  When they took that out and installed the Super Air Knives, there was no net increase in noise level…it remained at 93dBA.

THEN came the even better part: Compressed air consumption was reduced to about 30% of what the drilled pipe was using.  Right in line with our table above.  Just another validation of the trustworthiness of our published data.  As EXAIR’s President is fond of saying, “Claims are easy, proof is hard.”

If you’re looking for a quiet, efficient – and effective – solution for a compressed air product application, give me a call.

Russ Bowman
Application Engineer
Find us on the Web
Follow me on Twitter
Like us on Facebook

Labor Day 2017

What does Labor Day mean to you? Summer’s last hurrah? An extra day to sleep in, extend a weekend trip, or (ugh) tackle a home improvement project? Something else entirely, or all of the above? I neither expect, nor want, this to change any plans or mindset, but as U.S. federal holidays go, I find the history and meaning of Labor Day to be fascinating.

Maybe not as fascinating as Mister Spock preparing to drop the bass, but still pretty fascinating.

1777 – The first unions were organized in the United States by printers, carpenters and shoemakers, seeking better wages and shorter hours.

1825 – The United Tailoresses of New York, the first all-women’s union, is formed in New York City.

1827 – The Mechanics Union of Trade Associations forms in Philadelphia to call for a standardized 10-hour workday.

1840 – President Martin Van Buren establishes a 10-hour workday for federal workers.

1868 – The first federal 8-hour labor law is passed, but only applies to a small group of federal workers.

1885-1886 – Several municipalities around the United States declare Labor Day ordinances – a day of rest to recognize the social and economic achievements of American workers.

1887 – Oregon passes the first state-wide Labor Day observance law.  Colorado, Massachusetts, New Jersey, and New York follow suit this same year.

1891 – Labor Day is established as a national holiday by the Congress of the United States.

I don’t have the space (or the will) to get in to a detailed discourse on the highs (and lows) of the achievements (and setbacks) of the American working class through the 20th Century.  If I did, I’d choose to focus on the positive.  Almost everyone I know who’s in the American work force – family, friends, neighbors, and especially my co-workers at EXAIR – enjoys a safe work environment, fair wages & benefits, and opportunities unavailable anywhere else in the world.  So, Monday, I’ll take the day off that our forebears fought and earned for us.

If you’d like to talk about a compressed air product application, give me a call.  On Tuesday.

Russ Bowman
Application Engineer
Find us on the Web
Follow me on Twitter
Like us on Facebook

DJ Spock photo courtesy of geraldfordCreative Commons License

EXAIR Heavy Duty Safety Air Gun Reduces Noise Level and Saves Air!

Inside of the customer’s fin press

Just this week I’ve been working with an aerospace manufacturer that had some concerns about a cleaning operation on one of their fin press machines used for a stamping process. After each operation, they need to blow out the dies to remove any residual oil and debris. They were currently using a ¼” open copper tubing operating at 90 psi. Their reason for contacting EXAIR was due to a recent OSHA compliance training that their production manager had attended. He learned about OSHA 1910.242(b), a directive that we’ve written about many times in the past, that states compressed air devices used for blowoff must maintain a dead-end pressure less than 30 psi. Additionally, the sound levels were far too high to adhere to OSHA directive 29 CFR 1910.95(a). This was a major concern for them and a common theme that we hear from many of our customers. As this manufacturer is clearly aware, fines associated with failing to comply to OSHA directives can be quite costly. Their failure to adhere to this and a few other directives led to a total penalty of $33,800.00.

EXAIR’s Heavy Duty Safety Air Gun with Chip Shield

After some discussion about the different types of solutions that EXAIR has to offer, we settled on the Model 1310-18-CS. At a sound level of just 74 dBA when operated at 80 psi, we were able to drastically improve upon the sound levels that he was previously experiencing. This was a very welcomed solution by his operators, as they were now able to clean out the dies without having to wear any hearing protection. The Chip Shield also added some additional protection so that no debris could come back towards the operator. In addition to addressing his sound level concerns, we were also able to save a substantial amount of compressed air. The 1310-18-CS will consume just 14 SCFM of compressed air at 80 psi. A ¼” pipe operated at this pressure will consume approximately 69 SCFM. This is an 80% reduction in compressed air usage for just one operation!!

If you have an application where sound level needs to be reduced or you’re looking to improve upon employee safety, EXAIR has the solution. Give us a call today to find out how we can implement a solution to keep OSHA inspectors at bay.

Tyler Daniel
Application Engineer
Twitter: @EXAIR_TD

OSHA 29 CFR 1910.95 – Standard on Occupational Noise Exposure

Last week, the EXAIR Blog featured an article about the OSHA Standard 1910.242(b) – Reduction of Air Pressure below 30 psi for Cleaning Purposes.  This week, we will review another OSHA standard that affects many of you in manufacturing and other industries.

OSHA 29 CFR 1910.95 – Standard on Occupational Noise Exposure discusses the effects of noise and sets limits for exposure.  Occupational noise can cause hearing loss, and also interfere with concentration and communication, disrupting the job performance. Below is a summary from the standard of the Permissible Noise Exposure (OSHA Table G-16)

OSHA Noise Level

From the chart, the time an employee can be exposed to loud noise is greatly reduced as the sound level goes up.   The use of hearing protection is helpful but relies on the operator to use consistently and correctly.  Ear plugs or ear muffs can be uncomfortable and hot, leading to possible reduced usage.  OSHA can come on site, and if violations to the sound level exposure limits are found, they can impose fines and mandate corrective action be taken place.

The recommended course of action when an operator is subjected to sound exceeding those in the chart above is to enable feasible administrative or engineering controls. Engineering controls is the arena in which EXAIR can be a great resource.

The first step in understanding and addressing any sound level issues is to measure the sound. The easy to use Digital Sound Meter, model 9104 shown below, allows for accurate testing of noise levels throughout the facility.  Noisy areas can be quickly identified, leading to review, design and implementation of the engineering controls.


Some of the worst offenders for noise violations is compressed air usage.  A prime example would be inefficient blowoffs, used for cooling, drying, or cleaning.  Open pipe, copper tube or drilled pipe are a few of the common culprits.  Not only do they consume excessive amounts of compressed air, they can produce noise levels above 100 dBA.

EXAIR manufactures a wide variety of engineered products that utilize compressed air and deliver it in a controlled manner.  This allows for the most efficient use of compressed air and keeps the sound levels much lower than the inefficient methods.  A Super Air Knife can replace a drilled pipe, reducing sound by as much as 20 dBA, while using 50-70% less compressed air.  An engineered Super Air Nozzle can replace an open pipe or copper tube and reduce sound levels down to 74 dBA, and even down to 58 dBA for the smallest available nozzles.

EXAIR has been providing Intelligent Compressed Air Products since 1983.

If you have questions regarding noise limits and how to solve any issue with an EXAIR Intelligent Compressed Air® Product, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer

Send me an email
Find us on the Web 
Like us on Facebook
Twitter: @EXAIR_BB