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.


Engineered Air Nozzles Reduce Noise Levels and Outlet Pressure, Meeting OSHA Requirements

“My operators are complaining that our air guns are too loud, how can you help me?” – is a very common inquiry we receive here at EXAIR on almost a daily basis. Many open end blowoffs or air guns fitted with nozzles that have cross drilled relief holes create high pitch wind shear, resulting in excessive noise levels, sometimes exceeding 100+ dBA. This not only is a safety concern but also an OSHA violation.

Variety of Air Nozzles that produce dangerously loud noise levels

Loud noises and the length of exposure time can lead to significant health concerns such as long term hearing loss, increased stress levels and potential injury due to lack of concentration. The Occupation Safety and Health Administration (OSHA) introduced Standard 29 CFR 1910.95(a) as a way to protect workers from job related injuries associated to potentially dangerous sound levels. Per the Standard, at 90 dBA an operator is limited to a maximum of 8 hours of constant exposure. As noise levels increase, the allowable exposure time decreases, in some cases slowing production, costing a company on their bottom line.


EXAIR’s Air Nozzles are engineered so they entrain surrounding air across the profile of the nozzle, which produces a smoother airflow, ultimately reducing wind shear, resulting in much lower sound levels, meeting the OSHA Standard.

Illustration showing the air travel of our Super Air Nozzles


In addition, our Air Nozzles also meet the OSHA Standard 1910.242(b) for 30 PSI dead end pressure. All of our engineered Air Nozzles provide a relief or a safe path for the air to exit if the nozzle were to be blocked or pressed against an operator’s body so the exiting air pressure will never reach 30 PSIG.

All of EXAIR’s Air Nozzles are available with standard NPT threads to easily adapt to existing air guns. We also off our full line of Safety Air Guns which are fitted with our engineered nozzles, providing an “off-the-shelf” OSHA compliant solution. For help selecting the best product to replace your existing device or if you have a new application you would like to discuss, give us a call at 800-903-9247.

Justin Nicholl
Application Engineer


Air Nozzles Blowoff Guide Available For FREE

Are you looking for an engineered Air Nozzle to replace your existing unsafe open pipe? Maybe you are wanting to reduce the sound level in your facility or decrease your energy costs? EXAIR offers a large variety of Air Nozzles that are ALL OSHA compliant to meet or exceed OSHA Standard 1910.242(b), by eliminating any potential for dead-ending the air flow out of the nozzle and keeping the outlet pressure safe. The design of our Super Air Nozzles ejects the compressed  air behind a series of fins so there is always path for the air to escape, meaning they cannot be dead ended.

OSHA Noise Level
ALL of EXAIR’s Air Nozzles meet or exceed noise exposure levels.

In addition, our air nozzles meet the OSHA Standard 29 CFR – 1910.95(a) for allowable noise exposure levels. Excessive noise in the workplace can cause stress, lack of concentration leading to accidents and potential long term hearing loss (More OSHA Noise Induced Hearing Loss info here). EXAIR’s air nozzles entrain surrounding ambient air up to 25 times for every 1 part of compressed air, producing much less wind shear, reducing the output sound level, while also making our units more efficient, consuming less compressed air.


air nozzle flow
How our Super Air Nozzles entrain surrounding air.

We offer nozzles from our smallest offering with a tiny M4 thread up to our largest 1-1/4 NPT unit, with varying force from 2 ounces up to 23 lbs., in zinc aluminum, stainless steel, brass or PEEK plastic.

With such a vast offering, we understand selection can seem difficult. To simplify the process we offer our Air Nozzles Blowoff Guide. Our FREE Blowoff Guide has all the information available in regards to force, dimensions, air flow patterns, air consumption and materials.You will also find detailed information about our full product line of Safety Air Guns as well.

blowoff guide
Order our complimentary Blowoff Guide today!

To order our complimentary blowoff guide, please click here. If you need additional information, please give us a call at 800-903-9247.

Justin Nicholl
Application Engineer


Chain-Chain-Change, Change Out That Drilled Pipe…

Life is full of change.  It might sound trite, but truer words were never spoken.  I used to get up around 6:30 on work days.  Now, thanks to my son’s middle school schedule, I’m usually seeing him out the door at that time.  Getting up earlier was certainly a difficult change at first, but it’s had its benefits.  Not the least of which is spending a little extra time with the boy in the morning.

One of our favorite things to do while eating breakfast is to watch the ‘How things are made’ types of shows. Of course, watching these types of shows with an engineer has its downside.  While we can usually explain exactly what’s happening in the process of whatever is being made, the problem is that we often do.  Meaning we wind up talking over the program, which, ironically, is one of my greatest pet peeves.  Speaking of change, guess that’s something I need to work on…


At any rate, this morning we saw a show on making saltines.  At the sight of the copper pipe positioned near where the cracker dough comes off the die-cut wheel, I knew exactly what was up. ‘They’re using drilled pipe! That’s not safe and a HUGE waste of compressed air!  That’s the perfect application for a Super Air Knife!”  Guess watching these programs with an EXAIR engineer has an additional risk: We can get a little over-excited when we see OSHA violations and wastes of compressed air! I think I about made my son jump out of his gym shorts, but he’s watched these sorts of shows with me before.  He knew the risks…

Life is full of change, and while perhaps I can get better at not talking while the TV show is on, I doubt I’ll ever stop cringing at safety violations and wasting compressed air.  Do you have drilled pipe in your plant?  If so, you could be in violation of multiple safety standards and are definitely wasting money on compressed air.  EXAIR can help you minimize harmful noise levels and keep you in compliance with OSHA’s dead-end pressure standard. Please give EXAIR a call to begin saving air and increasing safety!

Dan Preston



Safe Trip

Just getting back in the swing of things after being on vacation last week. My family, along with my mother, went on a 7 day Eastern Caribbean cruise which included 3 days at sea and 3 days at different ports. Our port stops included the Bahamas, San Juan Puerto Rico and the island of St. Maarten. My wife and I have cruised several times and have already visited these islands, but with this cruise being our son’s and my mother’s first, we thought we would try to experience some different things.

Our last port was St. Maarten, where “we” (my wife and mother) planned our day of shopping and having an authentic lunch at a local restaurant. With the shopping portion of the day complete, we started asking locals for a good place to have lunch. We met a local who ran his own taxi company and recommended we have lunch at Maho Beach but it was going to be a 20 minute taxi ride. When we arrived, for some reason the area seemed somewhat familiar and then it hit me…. I’ve seen this place on TV! Their airport sits right on the edge of the island and arriving and departing planes basically fly right over your head while sitting at the restaurant/bar or swimming at the beach.

People line up along the road and fence line and wait for the next plane (the restaurant/bar has arrival and departure screens and will yell out when a large commercial jetliner is approaching), making it a very crowded area. Due to the potential jet blast coming from the engines there are safety signs posted that people ignore. I did ask one of the restaurant/bar managers if safety is such a concern, then why do they allow people to line up and he said “all they can do is warn people, if they want to subject themselves to injury, then that’s on them”. I don’t want to see anyone getting hurt, but I must admit, it is a little humorous to see people get blown all over the beach. Needless to say, we stood a good distance away.

St Maarten02_Maho Beach38Safety signmaho-beach-st-maarten

In all seriousness, safety should be a primary concern. Is your plant currently practicing safety when dealing with compressed air? Open pipes, tubes or drilled pipe can consume large amounts of compressed air, and exceed the pressure and noise level thresholds outlined by OSHA. And we are all aware that personnel don’t always abide by the safety rules – much like ignoring a safety sign.

At EXAIR, our customer’s safety is of utmost importance. All of our intelligent compressed air products meet or exceed the OSHA standard 1910.242(b) for safety.  This means that you can still operate the devices at 80 psig while not having to worry about an operator injuring themselves with the compressed air.  This is not just for one product line, but ALL of the compressed air products that we manufacture.

EXAIR products also meet or exceed the OSHA standard 29 CFR 1910.95(a) for maximum allowable noise exposure levels.   The chart for allowable noise level exposure is below. Occupational hearing loss is a serious issue in manufacturing, in fact, it is the most commonly recorded illness is manufacturing. Engineering controls, like replacing open air lines with engineered air nozzles, are one of the top recommendations to solve the problem. Engineering controls can effectively eliminate the problem of people forgetting, refusing, or ignoring safety processes.

OSHA Noise Level

By implementing the EXAIR engineered solutions into your facility you can effectively lower the noise level cause by unsafe compressed air blow offs and possibly eliminate the need for hearing protection all together.   In my experience any time an operator doesn’t need to wear hearing protection or you can make their surrounding environment a little quieter, they tend to be a little happier which, always leads to better production. Again, many resources back this up, loud noise can also create physical and psychological stress.

These are just two of the standards that EXAIR will never take a vacation on.   Every product that EXAIR designs must be safe for operator operations, whether that be through pressure output or through the noise level it creates.

Contact one of our applications engineers to see how we may be able to improve similar safety concerns at your facility.

Justin Nicholl
Application Engineer