Understanding Noise: Sound Power Vs. Sound Pressure

Sound Power and Sound Pressure have been covered a few other times here on the EXAIR Blog. Once here by Brian who made the visual correlation in regards to a speaker and a musical instrument. And here by Russ who breaks down how you calculate sound power level with the below equation!
Sound Power Equation
too lou Sound Power Level Equation
All machines generate sound when they are in operation. The propagated sound waves cause small changes in the ambient air pressure while traveling. A sound source produces sound power and this generates a sound pressure fluctuation in the air. Sound power is the cause of this, whereas sound pressure is the effect. To put it more simply, what we hear is sound pressure, but this sound pressure is caused by the sound power of the emitting sound source. To make a comparison, imagine for example a simple light bulb. The bulb’s power wattage (in W) represents the sound power, whereas the bulb’s light intensity represents the sound pressure.
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Light Bulb
Sound power does not generally depend on the environment. On the contrary, the sound pressure depends on the distance from the source and also on the acoustic environment where the sound wave is produced. In the case of indoor installations for example, sound pressure depends on the size of the room and on the sound absorption capacity of the surfaces. For instance, say the room walls don’t absorb all the sound but reflect parts of it, then the sound pressure will increase due to the so called reverberation effect. (reverberation time is broadly defined as the time it takes for the sound pressure to reduce by 60 dB after the sound emitting source has been shut off). 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. Jordan Shouse Application Engineer Send me an email Find us on the Web  Like us on Facebook Twitter: @EXAIR_JS Light Bulb image courtesy of  josh LightWork  Creative Commons License

Engineered Air Nozzles Keep Your Operations Safe

If you are looking for a way to save money and make your blow off applications safer, look no further than EXAIR’s Engineered Air Nozzles & Jets. By upgrading your blowoff, cooling, and drying operations to use one of our Super Air Nozzles or Jets you can save as much as 80% of your compressed air usage when compared with an inefficient solution. Plus you can remove open ended pipes and other unsafe blow offs that OSHA will fine you for.

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An open copper pipe or tube, even if “flattened” as we commonly see, wastes an excessive amount of compressed air. This wasted compressed air can create problems in the facility due to unnecessarily high energy costs, maintaining system pressure that can affect other processes and excessive noise exposure for personnel. An open pipe or tube will often produce sound levels in excess of 100 dBA. At these sound levels, according to OSHA, permanent hearing damage will occur in just 2 hours of exposure.

osha

By simply replacing the open tubes and pipe with an EXAIR Super Air Nozzle, you can quickly reduce air consumption AND reduce the sound level. Sound level isn’t the only thing an OSHA inspector is going to be concerned about regarding an open pipe blowoff, in addition OSHA 1910.242(b) states that a compressed air nozzle used for blowoff or cleaning purposes cannot be dead-ended when using with pressures in excess of 30 psig. I don’t know if you’ve ever tried to use an air gun with 30 psig fed to it, but the effectiveness of it is dramatically reduced. This is why there needs to be a device installed that’ll prevent it from being dead-ended so that you can operate at a higher pressure.

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EXAIR’s Super Air Nozzles are designed for maximum performance and safety. The engineered features keep EXAIR nozzles running quietly, and cannot be dead-ended. Using an OSHA compliant compressed air nozzle for all points where a blowoff operation is being performed should be a priority. Each individual OSHA infraction will result in a fine if you’re surprised with an OSHA inspection. Inspections are typically unannounced, so it’s important to take a look around your shop and make sure you’re using approved products.

You’ll find all of the tools you need in the EXAIR catalog. Click here if you’d like a hard copy sent directly to you! Or, get in touch with us today to find out how you can get saving with an Intelligent Compressed Air Product.

Jordan Shouse
Application Engineer

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EXAIR Flat Air Nozzles: Powerful, Quiet, Safe and Adjustable

Are you tired of your current compressed air being so loud? Well then, we have a solution for you; EXAIR’s Flat Super Air Nozzles. The patented design of the 1” and 2” Flat Super Air Nozzles makes it great for applications that require a powerful but precise flat stream of air. The Flat Super Air Nozzles work much like our Super Air Knives, the main difference being that the Flat Super Air Nozzles provides a more forceful stream of air. The design of the Flat Super Air Nozzles also provides a greatly reduced sound level.

2″ Flat Super Air Nozzle

EXAIR’s Flat Super Air Nozzles are safe, reliable, and efficient. The nozzles are specifically designed in a way to prevent dead head pressure as stated in OSHA Standard 1910.242(b). The directive stats that compressed air used for cleaning purposes can not exceed a dead-end pressure of 30 psig. If a dead-end pressure were to exceed that pressure then there is potential for an air embolism to form. EXAIR has designed our Flat Super Air Nozzles so that they cannot be dead-ended; this allows you to run at a typical 80-100 psig from your compressed air system.

Various Applications of Flat Super Air Nozzles

EXAIR Flat Super Air Nozzles are designed to also be quiet while operating at those higher pressures. When operating at 80 psig the 2” Flat Super Air Nozzle is going to have a sound level of 77 dBA were as the 1” Flat Super Air Nozzle when operated at 80 psig is going to have a sound level of 75 dBA. The higher the pressure the more air is going to flow through the nozzle; the more air flowing though the nozzle the louder it is going to be.

2″ Flat Super Air Nozzle

EXAIR’s High Power Flat Super Air Nozzles are designed for those tougher applications where you need more force, and will operate at slightly louder levels. The HP series Flat Super Air Nozzles have a thicker shim in them that allows for more air to escape out the end delivering a high force. The High powered 2” Flat Super Air Nozzle when operated at 80 psig has a sound level of 83 dBA where the 1” is only 82 dBA.

All of EXAIR’s flat Super Air Nozzles are designed with an internal patented shim which allows for adjusting the total volume of airflow and force that the nozzle produces. These shims are available in different thicknesses and aid in keeping noise levels down, provide gross adjustment of airflow and the flexibility for achieving a successful application. 

If you have any questions or want more information on EXAIR’s Flat Super Air Nozzles or any of our products, give us a call, we have a team of application engineers ready to answer your questions and recommend a solution for your applications.

Cody Biehle
Application Engineer
EXAIR Corporation
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What’s So Great About Air Entrainment?

Air entrainment is the phenomenon that occurs when air (or any gas) under pressure is released from a device in such a way that a low pressure is generated in the immediate area of the air (or gas) discharge.  Air (or gas) from the surrounding environment is then pulled (or entrained) into the discharged air stream, increasing its volumetric flow rate.  EXAIR Corporation has been engineering & manufacturing compressed air products to take maximum advantage of this phenomena since 1983…and we’ve gotten better & better at it over the past 36 years.

Obviously, the first thing that’s so great about air entrainment is…free air flow.  Every cubic foot that’s entrained means that’s a cubic foot that your compressor didn’t have to spend energy compressing.  Considering the EXAIR Super Air Knife’s entrainment ratio of 40:1, that makes for a VERY efficient use of your compressed air.

Another thing that’s so great about air entrainment is…it’s quiet.  As you can see from the graphic at the top of this blog, the Super Air Knife entrains air (the lighter, curved blue arrows) into the primary compressed air stream (the darker, straight blue arrows) from above and below.  The outer layers of the total developed flow are lower in velocity, and serve as a sound-attenuating boundary layer.  The sound level of a Super Air Knife (any length…here’s why) is only 69dBA.  That means if you’re talking with someone and a Super Air Knife is running right next to you, you can still use your “inside voice” and continue your conversation, unaffected by the sound of the air flow.

I always thought it would be helpful to have more than just a graphic with blue arrows to show the effect & magnitude of air entrainment.  A while back, I accidentally stumbled across a stunning visual depiction of just that, using a Super Air Knife.  I had the pleasure of talking with a caller about how effective a Super Air Knife might be in blowing light gauge paperboard pieces.  So I set one up in the EXAIR Demo Room, blowing straight upwards, and tossed paper plates into the air flow.  It worked just as expected, until one of the paper plates got a little closer to the Super Air Knife than I had planned:

As you can see, the tremendous amount of air flow being entrained…from both sides…was sufficient to pull in lightweight objects and ‘stick’ them to the surface that the entrained air was being drawn past.  While it doesn’t empirically prove the 40:1 ratio, it indisputably demonstrates that an awful lot of air is moving there.

If you’re looking for a quiet, efficient, and OSHA compliant solution for cleaning, blow off, drying, cooling…anything you need an even, consistent curtain of air flow for – look no further than the EXAIR Super Air Knife.  If you’d like to discuss a particular application and/or product selection, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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