Measuring and Adding Sounds


My colleague, Russ Bowman, wrote a blog about “Sound Power Level and Sound Pressure”.  He discussed the logarithmic equations around sound.  I will be discussing what happens when you have more than one sound source, as often heard within manufacturing plants.  Sounds can be added together to determine the overall sound level that your hear.  This is very important when it comes to minimizing hearing loss.

In looking at a single source of sound, sound pressure is created by the loudness of a noise.  The units are measured in Pascals.  The lowest pressure perceived by human hearing is 0.00002 Pa, and we can use this value as a reference point.  From sound pressures, we can arrive to a sound pressure level which is measured in decibel, dB.  This correlation between sound pressures and sound pressure levels are calculated by Equation 1:



L – Sound Pressure Level, dB

P – Sound pressure, Pa

Pref – reference sound pressure, 0.00002 Pa

As an example, the sound pressure from a passenger car as heard from the roadside is 0.1 Pa.  With Equation 1, we can get the following decibel level:

L = 20 * Log10 (0.1Pa/0.00002Pa) = 74 dB

Because human ears are sensitive to different frequencies, the sound pressure levels can be modified, or weighted, to indicate an effective loudness level for humans.  This adjustment is done in two different ways; A-weighting and C-weighting.  The C-weighting is for very loud noises with high peaks or sharp impacts like gunfire. The A-weighting is the most commonly used value as the sound pressure levels are adjusted by the frequency level.  For higher and lower frequencies, the change in the sound value is much greater than the mid-level frequencies that are within our hearing range.  Sound measurements for safety are measured in the A-weighted scale.  OSHA created a chart in the 29CFR-1910.95(a) standard that shows the noise levels over exposure times for an operator.  To use the OSHA chart accurately, the total noise level in dBA should be calculated.

OSHA Chart

To determine the total sound level, we can add all the sound pressure levels together by Equation 2:



Where L1, L2… represents the sound pressure level in dBA for each sound source.

As an example, a manufacturing plant had an operator using a machine that had four copper tubes to blow off a cutting operation (reference photo below).

Blow off station

The decibel level for a copper tube was measured at 98 dBA.  The total amount of sound that the operator was exposed to was determined by Equation 2 with four values.

L = 10 * log10 (109.8 + 109.8 + 109.8 + 109.8)

L = 104 dBA

In looking at the OSHA chart, the operator would only be allowed to operate the machine only a little over one hour without hearing protection.  In this same example, we replaced the copper tubes with an EXAIR Super Air Nozzle, model 1110SS.  The noise level for each nozzle is 74 dBA.  By replacing all four copper tubes with Super Air Nozzles, Equation 2 becomes:

L = 10 * log10 (107.4 + 107.4+ 107.4 + 107.4)

L = 80 dBA

The total sound level is now in accordance with OSHA regulations for the operator to work all 8 hours at the machine without hearing protection.

A commonly used acronym in hearing safety is NIHL, or Noise Induced Hearing Loss.  To keep your operators safe and reduce NIHL, it is important to measure the total sound level.  As a protocol in safety, it is a requirement to use engineering standards before purchasing personal protective equipment or PPE.  For the customer above, they followed that protocol with our Super Air Nozzles.  If you need to reduce noise levels in your facility by engineering standards, EXAIR offers a large line of blow-off products that can meet the safety requirements.


John Ball
Application Engineer
Twitter: @EXAIR_jb


Photo of Ear auricle Listen by geraitCC0 Create Commons.


People of Interest: Daniel Bernoulli – 2/8/1700 to 3/17/1782

Daniel Bernoulli was born in Groningen, Netherlands on February 8, 1700  and was part of a large family heritage of famous mathematicians – His father Johann Bernoulli, one of the first founders of calculus, his uncle Jacob Bernoulli and his older brother Nicolous. When he was only 7 years old, Daniel began to take an interest in mathematics but his father convinced him that there was no financial gain to be had in mathematics and recommended he focus his studies in business instead. Reluctant at first, Daniel would take his father’s advice under the one condition, that his father would tutor him in calculus and his theories of kinetic energy.

At 13 years old, Daniel attended Basel University where he studied logic and philosophy completing his bachelor’s degree by the age of 15 and earning his master’s degree just 1 year later. Over the years, Daniel’s relationship with his father was strained as a result of him plagiarizing his father’s findings. Eventually, his father passed without reconciling with Daniel. At 24, Daniel became a Professor of Mathematics  at a University in Venice but resigned from the position just 9 years later in 1733.

His most recognized mathematical contribution, Bernoulli’s principle, came in 1938 while performing energy conservation experiments, and he published the results in his book entitled Hydrodynamica . He discovered that when fluid travels through a wide pipe into a smaller, more narrow pipe, the fluid begins to move  faster. He determined that the volume or amount of fluid moving through the pipe remains unchanged but will conform to the shape of the pipe or container as it flows. He concluded that the higher the pressure, the slower the flow of the liquid and the lower the pressure, the faster the liquid flow.

The same principle can be applied to air. As air moves around an obstruction or object, it follows the profile of the part and begins to speed up.

Take for example our Super Air Nozzles. The compressed air exits the nozzle through a series of jets which induces a low pressure around the profile of the nozzle, drawing in ambient air. This entrainment of air, up to 25 times or more, results in a high outlet flow at minimal compressed air consumption.

Super Air Nozzle air entrainment

Many of the products offered by EXAIR incorporate this science which can lead to a more efficient operation by lowering compressed air demand ultimately reducing operating costs. To see how our products can help you save money while increasing process performance, contact an Application Engineer for assistance.

Justin Nicholl
Application Engineer


Bildnis des Daniel Bernoullius image courtesy of Universitätsbibliothek Leipzig via creative commons license


Intelligent Compressed Air: Utilization of the Coanda Effect

Henri Coanda was a Romanian aeronautical engineer most known for his work developing what is today known as the Coanda effect. The Coanda effect is the propensity of a fluid to adhere to the walls of a curved surface. A moving stream of fluid will follow the curvature of the surface rather than continuing to travel in a straight line.  This effect is used in the design of an airplane wing to produce lift. The top of the wing is curved whereas the bottom of the wing remains straight. As the air comes across the wing, it adheres to the curved surface, causing it to slow down and create a higher pressure on the underside of the wing. This  is referred to as lift and is what allows an airplane to fly.


The Coanda effect is also the driving force behind many of EXAIR’s Intelligent Compressed Air Products. Throughout the catalog you’ll see us talking about air amplification ratios. EXAIR products are designed to take advantage of this phenomenon and entrain ambient air into the primary air stream. Compressed air is ejected through the small orifices creating air motion in their surroundings. Using just a small amount of compressed air as the power source, Super Air Knives, Air Nozzles, and Air Amplifiers all draw in “free” ambient air amplifying both the force and the volume of airflow.

EXAIR Intelligent Compressed Air Products such as (left to right) the Air Wipe, Super Air Knife, Super Air Nozzle, and Air Amplifier are engineered to entrain enormous amounts of air from the surrounding environment.

Super Air Knives provide the greatest amount of air amplification at a rate of 40:1, one part being the compressed air supply and 40 parts ambient air from the environment. The design of the Super Air Knife allows air to be entrained at the top and bottom of the knife, maximizing the overall volume of air. Super Air Nozzles and Super Air Amplifiers also use this effect to provide air amplification ratios of up to 25:1, depending on the model.

Air Amplifiers use the Coanda Effect to generate high flow with low consumption.

The patented shim design of the Super Air Amplifier allows it to pull in dramatic amounts of free surrounding air while keeping sound levels as low as 69 dBA at 80 psig! The compressed air adheres to the Coanda profile of the plug and is directed at a high velocity through a ring-shaped nozzle. It adheres to the inside of the plug and is directed towards the outlet, inducing a high volume of surrounding air into the primary air stream. Take a look at this video below that demonstrates the air entrainment of a Super Air Amplifier with dry ice:

Utilizing the Coanda effect allows for massive compressed air savings. If you would like to discuss further how this effect is applied to our Super Air Knives, Air Amplifiers, and Air Nozzles give us a call. We’d be happy to help you replace an inefficient solution with an Engineered Intelligent Compressed Air Product.

Tyler Daniel
Application Engineer
Twitter: @EXAIR_TD

EXAIR Heavy Duty Safety Air Gun With Accessories Improves Effectiveness and Safety

Model 1310-12 Heavy Duty Safety Air Gun, With 12″ Extension & 1100 Super Air Nozzle

In rugged industrial environments the EXAIR Heavy Duty Safety Air Gun delivers powerful blasts of compressed air right where it is needed.  It features a 3/8 NPT metal inlet to allow for increased air flow to the Super Air Nozzle of your choice and there are many configurations are available from stock.  It is constructed of a durable and robust cast aluminum body with an ergonomic and comfortable composite grip that allows for extended use without fatigue.

The Heavy Duty Safety Air Gun can be configured with extensions that are available in 6” increments up to 24” in length and 12” increments from 24” up to 72”.  Combine the extension with our optional Chip Shield for maximum operator safety and comfort.


Extension Tubes For Air Guns
Different Length Extensions For Every Application


Chip Shield
Chip Shields Offer Safety & Comfort For Operators

We offer a wide variety of nozzles to allow you to configure the Heavy Duty Safety Air Gun to you specific application.  EXAIR has a large selection of nozzles that are engineered to entrain surrounding air with the compressed air supply creating a synergistic blast that is very powerful.  Most importantly they operate much quieter than the limits of OSHA standard 29 CFR 1910.95(a) and can’t be “dead ended” therefore meeting OSHA standard 29 CFR 1910.242(b).

OSHA Chart
OSHA Maximum Allowable Noise Exposure


The EXAIR Heavy Duty Safety Air Gun is available in the configurations shown below or many others.  If you have an application you would like to discuss or to see how the Heavy Duty  Safety Air Guns will improve your process, give us a call, we are happy to help.

Heavy Duty Safety Air Gun Configuration Chart
Heavy Duty Safety Air Gun Sample Configurations

Steve Harrison
Application Engineer
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Improving Auger Cleaning Process Using 2″ Flat Super Air Nozzles And Swivels

I recently worked with a customer who was looking to improve the cleaning process on the  inside of one of their screw augers. They were currently using a couple of 1/4″ pipes as air wands to clean the left over powder on the auger blades and direct it toward a chute at the bottom which fed into another auger used for recovery. While the setup worked somewhat, they were concerned with the amount of air they were using as well as the OSHA safety concerns associated to using open ended pipes and excessive noise levels.

The customer was able to send a sketch of their current setup and after some further conversations, I recommended our Model # 1122 2″ Flat Super Air Nozzle and our Model # 9053 1/4″ NPT Swivel Fitting. The 2″ Flat Super Air Nozzle produces a 2″ wide, high velocity laminar airflow and uses only 21.8 SCFM (80 PSIG) while maintaining a low sound level of only 77 dBA. The Swivel Fitting allows for 50 degrees of movement, so they can achieve the best angle to direct the air to the critical areas.

2″ Flat Super Air Nozzle
Swivel Fittings available from M4 up to 1″ NPT

All of our Air Nozzles are engineered to meet or exceed OSHA Standard 1910.24(b) for 30 PSIG dead end pressure, they cannot be dead-ended, there is always a path for the air to safely exit so the outlet pressure will never reach 30 PSIG. In addition, our products are going to meet the OSHA Standard CFR 29 – 1910.95(a) for allowable noise exposure levels as well.

If you are looking to reduce air consumption and noise while improving operator safety, give us a call at 800-903-9247 for assistance.

Justin Nicholl
Application Engineer

Blowoff Systems Makes it Easy to Clean Extrusions

A metal cutting facility would cut pieces of aluminum extrusions, bars and cylinders to specific lengths as requested by their customers.  They used a variety of different types of cutting equipment depending on the size and profile, but every cutting machine would use coolant. At the end of the cutting process, they would run the parts through a washing system to remove any coolant and then through an inkjet marking system.  They would print the corresponding tag information on the top of each product.

The surface had to be dry or the ink would run and become illegible.  To try and speed up the drying process, they attached four soft copper tubes to blow compressed air along the top of the parts.  They flattened the ends slightly to give a wider blowing area as well as to direct the air into the T-slots of the extrusions.  The customer liked the flexibility of the copper tubes as they would need to change the position often to fit the appropriate size and profile.

The problem that they had with their setup was that the blowing was too loud and it used a large amount of compressed air.  They found EXAIR which looked to have a better solution to blow off the water from the product.

Blow Off Application

The customer gave some additional details on their process.  They could cut a wide range of diameters from 2 inches (51 mm) to 12 inches (305 mm) within their bar and cylinder stock.  They also would cut square and rectangular extrusions that had a variety of profiles and dimensions.  They requested a flexible product that could conform to the different sizes and types and also be adjusted manually for optimum blowing positions.

1122-9412 Blowoff Kit

EXAIR offers a great product line that would fit their requirements for this application, the Blowoff Systems.  With their requested specifications, the flat blowing pattern and flexibility, it directed me to the model 1122-9412 Blowoff Kit.  This kit comes with a Magnetic Base, Flat Super Air Nozzles, and flexible Stay Set Hoses.  The model 1122-9412 has two 2” Flat Super Air Nozzles which will give a wide blowing area.

The Magnetic Base contains two outlets with shut off valves on each port to allow for an easy way to turn off a nozzle when not needed for the smaller products.  Between the Magnetic Base and the 2” Flat Super Air Nozzle, a 12” (305mm) long Stay Set Hoses connects them together which will allow for precise blowing and maneuverability.

By installing two pieces of the model 1122-9412 to his system, the customer was able to remove the four pieces of the copper tubing which were loud and inefficient.  The noise level dropped to 77 dBA with the 2” Flat Super Air Nozzles which was a relief, and they realized that the air compressor was working less.  By adding the Blowoff Kits to their system, they now had a flexible, efficient and effective way in drying the products prior to printing.

With the customer above, they saw much improvement in blowing off the water which kept the ink jet printing process from running or smearing.  If you need flexibility in your blowing application, EXAIR offers a variety of kits with different types of nozzles to accommodate the best blowing feature for your application.  If you would like to discuss these options, you can contact an EXAIR Application Engineer, and they will be happy to help.

John Ball
Application Engineer
Twitter: @EXAIR_jb

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
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