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.


Compressed Air and Safety


Compressed air is generally considered the fourth utility in industrial, commercial and back-yard settings.  It is used to power pneumatic equipment, cleaning surfaces, conveying materials, etc.  The compressor reduces the volume inside a chamber to increase the pressure.  The compressed air typically is contained in a reservoir tank for distribution to pneumatic equipment and devices.  Since air is a compressible fluid it has stored energy; and, if not used properly, it can be hazardous.  Most people perceive compressed air as harmless, but this is untrue.  It can be very dangerous.  Here are some potential risks when using compressed air:

  1. If the air pressure against the skin becomes greater than 30 PSI, air can penetrate through the membrane and cause an embolism which could be fatal.  The term used is Dead-End pressure, any end-use nozzle or blowoff product cannot exceed 30 PSI dead-end pressure.
  2. Hearing damage can occur from exposure to loud noises from compressed air exhausting from pneumatic equipment or devices.
  3. Proper use of Safety Air Guns and Safety Air Nozzles is a must. They should not be modified or tampered with.  For example, tying the trigger on an air gun for continuous blowing or modifying the nozzle to get a different blowing pattern.
  4. Compressed air can generate high velocities which can shoot chards of debris. The accelerated fragment can injure any part of the body even from bounce-back.
  5. If the air pressure is higher than the recommended rating for the equipment, uncontrolled eruptions can occur which can send broken pieces everywhere.
  6. When air hoses or lines are laying on the floor, near pinch points, or degrades from the environment, a break can occur causing unrestrained hose “whipping”.

Some safety precautions can be followed in your area when using compressed air products.  They may seem basic, but they are commonly overlooked.

  1. Verify that all compressed air components are rated to be used for the maximum line pressure.
  2. Use shut-off valves nearby to isolate the system from the main compressed air line.
  3. Have general inspection on your compressed air system to check for pipe degradation, leaks, faulty pneumatics, etc.
  4. When you go to repair items attached to the compressed air line, make sure to use proper lockout procedures to isolate and remove the hazardous energy.
  5. Remember that compressed air is not a toy and use proper PPE when required.
  6. If any pneumatically operated product is damaged, remove it from service and either repair it or replace it.
EXAIR Products

In 1970, Occupational Safety and Health Administration, OSHA, was enacted by the Department of Labor.  This organization was created “to ensure safe and healthful working conditions for working men and women”.  They created a set of laws and standards that they enforce with heavy fines and reoccurring visits if not followed.  The Department of Labor lists these laws under title 29 in the Code of Federal Regulations (CFR).  For general industry, these safety regulations are under part 1910 of 29 CFR.  To give a few examples, 29 CFR 1910.242b gives the explanation about dead-end pressure.  Under 29 CFR 1910.95a shows the maximum allowable noise exposure.  The reason that I noted these two OSHA standards as they are commonly overlooked with Safety Air Guns, and commonly fined by OSHA for improper nozzles.

Safety is everyone’s responsibility, and EXAIR products can be a key.  If you would like to discuss how to improve your workplace, you can contact an Application Engineer at EXAIR.     Because hazards and fines can be detrimental to your company when it comes to compressed air safety.

John Ball
Application Engineer

Twitter: @EXAIR_jb


Photo: Attention Warning Sign by Peter-LomasCreative Commons: CCO



EXAIR’s Soft Grip Safety Air Gun Provides Safety & Efficiency Benefits

The Soft Grip Safety Air Gun is in stock for immediate shipping and has a durable cast aluminum body that is suited for rugged industrial use.  The ergonomic design has a large trigger and a soft, comfortable grip for easy operation and keeps the hand in a comfortable position for extended periods of use. A convenient hook hanger allows for easy storage when not in use.  Aluminum Extensions (up to 72″ long) and Stay Set Hoses (up to 36″ long ) can be fitted, providing access to hard to reach places. Chip Shields are available for most models, protecting operators from flying debris, helping to meet an important part of OSHA’s requirements for the safe use of compressed air, OSHA Standard 1910.242(b).


The Soft Grip Safety Air Gun can be configured with over a dozen nozzle options, with air consumption as low as 2.5 SCFM @ 80 PSIG of supply pressure and up to 60 SCFM if needed.  Nozzle materials include Zinc Aluminum alloy, 316 Stainless Steel, and PEEK (a thermoplastic polymer.)

Use of an EXAIR Soft Grip Gun with an Engineered Air Nozzle will provide a safe and efficient use of compressed air, reduce energy costs, and eliminate harmful dead end pressures (again, helping to comply with the OSHA standard for safe use of compressed air.)

When outfitted with EXAIR’s engineered air nozzles, the Soft Grip Safety Air Gun is a powerful ally to reduce personnel noise exposure and protect them from noise induced hearing loss. This is another important safety feature complying with OSHA’s standard 29 CFR-1910.95(a).

The Soft Grip Safety Air Gun can be configured to meet applications from delicate blowoff of electronic circuit boards to large chip removal in metal cutting operations, and everything in between.

If you have questions regarding the Soft Grip Safety Air Gun, or would like to talk about any 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

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Twitter: @EXAIR_BB

Calibration – Keep Your Meters True

EXAIR offers meters to measure the level of physical parameters such as sound and static. Each meter has sensitive electrical circuitry and a periodic calibration is recommended to ensure the meter readings are tried and true.

The model 9104 Digital Sound Level Meter is an easy to use instrument that measures and monitors the sound level pressure in a wide variety of industrial environments. The source of loud noises can be quickly identified so that corrective measures can be taken to keep sound levels at or below OSHA maximum allowable exposure limits.

The sound meter comes from the factory with an NIST (National Institute of Standards and Technology) certificate of accuracy and calibration.  As a good practice, EXAIR recommends a yearly calibration of the instrument, and we offer a service that calibrates the unit to the same NIST standards and provide a written report of the calibration.

The model 7905 Static Meter allows easy one-hand static measurements.  It is useful in both locating sources of high static charge and checking the reduction of static after treatment with an EXAIR Static Elimination product.  The unit is sensitive and responsive, and indicates the the surface polarity of objects up to +/- 20 kV when measured from 1″ away.

It is also recommended that the Static Meter be calibrated on a yearly basis.  EXAIR offers (3) levels of calibration service.  The first two provide calibration in accordance with MIL Standards using accepted procedures and standards traceable to NIST.  The third calibration service conforms to the same Mil Standard, as well as ISO/IEC standards.

Annual calibration service of your EXAIR Digital Sound and Static Meter, along with proper care and storage, will keep your meter performing tried and true for many years, providing accurate and useful measurements.

To initiate a calibration service, give us a call and an Application Engineer will issue an Returned Good number, and provide instructions on how to ship the meter to EXAIR.

If you have questions regarding calibration services for your meters or would like to talk about any 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

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EXAIR Super Air Knives Helps Keep Labels on the Bottles.

Super Air Knife Blower Air Knife

Sometimes you need more power.  I received a phone call from a bottling facility that was currently using a blower style type of air knives.  They increased their production rate from 220 bottles/min to 300 bottles/minute, and they started to see issues in the labeling process.  Their operation consisted of a wash cycle, rinse cycle, drying cycle, then labeling.  They determined that the bottles were not getting dry enough during the drying cycle before the labels were applied.  They had a VFD (Variable Frequency Drive) for the blower system, and they reached the maximum rate.  Still the bottles were not getting dry enough to allow the label to stick to the surface properly.  This meant that they would have to increase the size of their blower system.  With the capital cost of a blower system, they decided to call EXAIR to see if we could help them with the drying application.

Compressed air is the best way for establishing a strong blowing force.  Instead of air pressures in the range of inches of water, the compressed air system can generate over 40 times the amount of pressure than a typical blower system.  EXAIR products uses this power of the compressed air to give you a wide range of blowing forces for drying, cooling, or moving products.  For the above application, I recommended two model 110212 Super Air Knife kits.  The kit includes the Super Air Knife, a filter, a regulator, and a shim set.  They mounted one knife on each side of the bottles to blow off and remove the liquid after the rinse cycle.  Even at the increased bottle speeds, the EXAIR Super Air Knives had no issues in keeping the bottles dry.  With the regulator and the shim, it was easy for them to dial in the correct amount of force without using excess compressed air.  The labels remained glued and the bottling process ran smoothly.  Because the company was impressed by the Super Air Knives, they wanted to comment on the comparisons between the blower knife and the Super Air Knife.

  1. Cost:
    1. Blower System – The reason for contacting EXAIR. Blower-type air knives are an expensive set up.  They require a blower, ducting, and a knife.  To have any flexibility, a control panel with a VFD will be needed.
    2. Super Air Knife – It is a fraction of the cost. With their system, we were roughly 1/10 the cost; even with the kit.  No capital expense report would be needed for the two air knives.
  2. Installation:
    1. Blower System – They stated that it took them a week to install the entire system before they were able to operate. They had to run electrical wires, controls, ducting, and they even had to change the conveying system slightly to accommodate the blower size.
    2. Super Air Knife – They mounted the filter and the regulator on the conveyor, and ran tubing to the Super Air Knives. Even with a fabricator making a bracket to fit into their system, they had the system up and running is less than two hours.
  3. Size:
    1. Blower System – The foot print of the blower is large and it takes up floor space. The 3” ducting had to be ran to an oversized air knife.  With the congestion of the bottle system, it made it difficult to optimize the position and the blowing angle to adequately dry the bottles.
    2. Super Air Knife – With the compact design, the Super Air Knife packs a large force in a small package. It has a footprint of 1 ¾” X 1 ½” X 12” long.  The air knife only required a ¼” NPT compressed air line to supply the compressed air.  It opened up the floor space as well as the bottling area.
  4. Maintenance:
    1. Blower System – The blower filter had to be changed regularly, and system had to be checked. Being that the blower motor is a mechanical device, the bearings will wear and the motor will fail over time.  These items should be checked quarterly as a PM which increase the cost to run the system.
    2. Super Air Knife – No moving parts to wear out. The only maintenance would be to change the filter once a year.
  5. Versatility:
    1. Blower System – They did have a VFD to control the blowing force. But it was still very limited.  With a 36% increase in the bottle speed, they went beyond the maximum capacity of the blower.
    2. Super Air Knife – With a regulator and the shim set, the blowing force can be controlled easily from a breeze to a blast. With their application, the customer only required 40 psig with a standard 0.002” shim to clean and dry the bottles.  They had the option to adjust the regulator or change the shim to get the appropriate amount of blowing force.  So, with any changes in the bottling operations, the Super Air Knife could easily be adjusted.  Also, with the blowing force being optimal from a distance of 3” to 12” from the target, they had more flexibility in angle and distance to hit the moving target.
  6. Quiet:
    1. Blower System – With the blower and turbulent air flow, the units are very loud. It had a sound level near 93 dBA, and with the operators working around the system, they needed PPE to protect them from the high potential of noise induced hearing loss.
    2. Super Air Knife – These units are very quiet. At 40 PSIG, the sound level is only at 61 dBA.  (Even operating at a pressure of 100 PSIG, the sound level is only 72 dBA).  This was very nice for the operators to work around as it wasn’t a constant noise nuisance.

In using the compressed air, the Super Air Knives are engineered to be very efficient.  The design creates a 40:1 amplification ratio which means that for every 1 part of compressed air, 40 parts of the ambient air is entrained.  But, even with the use of compressed air, the customer still wanted to share the ease of installing, the effectiveness of blowing, and the improvements to their process.  With the 6 points noted above, the customer wished that they would have contacted EXAIR at the beginning.

John Ball
Application Engineer
Twitter: @EXAIR_jb

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

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Twitter: @EXAIR_BB


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