The decibel is a unit of measurement that relates the ratio of a physical value to another value and is expressed on a logarithmic scale. The common symbol for decibel is dB. The decibel is used as a measure for many parameters in science and engineering such as acoustics (sound), electronics (power levels) and control theory.
The decibel originates from methods used to express performance and loss in telegraph and telephone circuits. The term ‘bel’ was coined in honor of Alexander Graham Bell, and the decibel, being 1/10th of a bel was established.
For most of us, the decibel is the familiar term relating to how loud a sound is.
With sound, the sound pressure is typically what is measured and is the local pressure deviation from the base or equilibrium atmospheric pressure, caused by a sound wave. In air, the sound pressure can be measured by a standard microphone, and is measured in pascals (Pa.)
To get to the common decibel reading we are familiar with, a little mathematics comes into play.
where Lp is the Sound Level in dB, prms is the measured sound pressure, and pref is the standard sound reference pressure of 20 micropascals.
The prms is what is measured by a microphone
Below are some representative sounds and the decibel rating – Note that sounds that are above 85 dB can cause hearing issues, and proper protection should be taken.
Some other interesting blogs about sound for you take a look at-
If you would like to talk about sound or any of the EXAIR Intelligent Compressed Air® Products, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.
OSHA Standard 29 CFR 1910.95(a), relating to permissible noise exposure levels, states that when employees are subjected to sounds in excess of 90 dBA, some type of control should be used to reduce the sound level. In an industrial setting, it’s very common to find the exhausting air from air operated devices such as actuators, diaphragm pumps or cylinders for example, to produce sound levels well above the allowable limits set forth in the Standard. EXAIR offers a variety of different Silencing Mufflers that help to reduce this noise level, while also increasing operator safety.
EXAIR’s Reclassifying Mufflers offer noise reduction up to 35 dB and are available in sizes ranging from 1/8″ to 1″ NPT. These types of mufflers are often considered”dual-purpose” as they not only reduce the noise level but also remove oil from the exhaust airflow by incorporating a removable filter element. The exhausting oil mist is reduced from 50 PPM (parts per million) to only 0.015 PPM, when the device is operated at 100 PSIG. In addition, there is a bowl on the bottom to capture any residual oil and a 1/4″ tube adaptor to allow for easy draining.
Sintered Bronze Mufflers are a relatively low cost option, commonly used with air cylinders as they can be installed quick and easy. We offer 1o different sizes, ranging from #10-32 for small installations, up to 1-1/2″ NPT for larger scale applications. The noise reduction depends on the size of the muffler and back pressure, which can occur from dirt or particulate clogging the muffler, restricting the exhausting airflow from passing through the porous sintered bronze.
Our Straight Through Mufflers are made of corrosion resistant aluminum and are lined with a sound absorbing foam, capable of reducing noise levels up to 20 dB. We offer 3 different sizes, 1/4″, 3/8″ and 3/4″ NPT, with a male thread on one end and female thread on the other. We incorporate this muffler design into our Cold Guns and Adjustable Spot Coolers and they are commonly used with our Vortex Tubes, Cabinet Cooler® Systems and E-Vac® Vacuum Generators as well.
Lastly, the Heavy Duty Mufflers feature an internal, 50 mesh stainless steel screen, to protect against contaminants in the airflow, and a corrosion resistant aluminum outer shell. In most cases, the sound reduction can be as high as 14 dB and we offer 2 different sizes, 1/4″ and 3/8″ FNPT. These types of mufflers are regularly used on the hot air exhaust of our Vortex Tubes.
For help with product selection or to discuss a particular process, please contact one of our application engineers at 800-903-9247.
EXAIR offers the model 9104 Digital Sound Level Meter. It is an easy to use instrument for measuring and monitoring the sound level pressures in and around equipment and other manufacturing processes.
Sound meters convert the movement of a thin membrane due to the pressure waves of sound into an electric signal that is processed and turned into a readable output, typically in dBA. The dBA scale is the weighted scale that most closely matches the human ear in terms of the sounds and frequencies that can be detected.
To protect workers in the workplace from suffering hearing loss OSHA has set limits to the time of exposure based on the sound level. The information in the OSHA Standard 29 CFR – 1910.95(a) is summarized below.
The Digital Sound Meter can be used to monitor and measure sound levels of manufacturing processed such as blowoffs for cooling or drying. Many blowoffs, especially open or drilled pipes are very inefficient and can be identified as a source of excessive noise, outside the OSHA exposure ranges. Once the noise violators are identified, a review can be done and the implementation of engineered solutions such as Super air Nozzles or Super Air Knives can be investigated. Keeping harmful noise levels in check benefits everyone involved.
The EXAIR Digital Sound Level Meter is an accurate and responsive instrument that measures the decibel level of the sound and displays the result on the large optionally back-lit LCD display. There is an “F/S” option to provide measurement in either ‘slow’ or ‘fast’ modes for stable or quickly varying noises. The ‘Max Hold’ function will capture and hold the maximum sound level, and update if a louder sound occurs.
Certification of accuracy and calibration traceable to NIST (National Institute of Standards and Technology) is included.
There is an informative Video Blog, presented by @EXAIR_LE that can be found here.
If you have questions about the Digital Sound Level Meter, or would like to talk about any of the quiet EXAIR Intelligent Compressed Air® Products, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Super Air Knife – No moving parts to wear out. The only maintenance would be to change the filter once a year.
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.
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.
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.
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.
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)
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.
From August 1st to September 30th, 2017, EXAIR will be giving away a 1” Flat Super Air Nozzle with a purchase of a Precision, Soft Grip, or Heavy Duty Safety Air Gun. We are promoting the importance of safety in the workplace with the EXAIR Safety Air Guns as well as the versatility of the different types of EXAIR nozzles. This promotional item, model 1126 nozzle, has a patented shim to blows a 1” wide stream of air to clean surfaces quickly and efficiently; a $43.00 complimentary gift (click on the link below).
Compressed air guns are one of the most commonly used pneumatic products in a manufacturing plant. They are used at workstations to blow off debris and to clean parts and tools. Because of the large quantities that are used in a plant; they are the most targeted by OSHA (Occupational Safety and Health Administration). Majority of the common brands of air guns fail to comply with two common violations, rule 29CFR 1910.95(a) for loudness and rule 29CFR 1910.242(b) for dead-end pressure. The reason is due to the nozzles that comes with the compressed air guns. Fines can get very expensive, and you can alleviate these penalties by purchasing an EXAIR Safety Air Gun. We are all responsible for safety; management, HSE department (Health and Safety Engineer), supervisors, and even the operators. Your compressed air guns should be assessed in your facility to evaluate your safe work environment.
With EXAIR Safety Air Guns, we supply an efficient, effective, and most important, safe air nozzle with all of our air guns. They are CE Compliant and exceed the OSHA sound level and dead-end pressure requirements. With substandard air guns, the operators would have to listen to loud noises all day and have to wear hearing protection. As for the dead-end pressure; the EXAIR nozzles are engineered to not allow the operator to completely close the end against the hand or skin. This is very important because if the pressure exceeds 30 PSIG, air can penetrate the skin and cause an air embolism. Some manufacturers place a restriction inside the air gun to comply with this standard, sacrificing the effectiveness of the blowing force. With our design, the compressed air is not able to be blocked; allowing the air to escape to atmosphere. Even with the compressed air system set to 100 PSIG, the pressure against the skin will not exceed 30 PSIG. Safety is a major concern for all of our customers and a priority for EXAIR in manufacturing our products.
As I mentioned above, the nozzles are one of the most significant parts in making a compressed air gun safe and OSHA compliant. In combining our engineered nozzles with a quality air gun, this makes the EXAIR Safety Air Guns one of the best products on the market. We currently have three different styles; the Precision, Soft Grip, and Heavy Duty. These Safety Air Guns are ergonomically designed to fit comfortable in your hand; and they come with quality trigger mechanisms and a durable valve assembly. The Precision Safety Air Gun is great for tight spaces and clearing out small holes. The Soft Grip Safety Air Gun provides extra comfort for long extended uses, and the Heavy Duty Safety Air Gun is a rugged, heavy duty industrial air gun. In combination with the EXAIR nozzles, the Safety Air Guns can offer another important attribute; we can save you money!!! Compressed air is very expensive to make, and with our Safety Air Guns, we use less compressed air but still create a strong blowing force. We do this by entraining the free ambient air into the air stream. If you increase the mass of air to the target, it will give you a hard hitting force to remove debris from surfaces or to clean tools and holes. The amplification ratio can be as much as 25 to 1. That means that for every 1 part of compressed air, the EXAIR Nozzles will entrain 25 parts of ambient air. So, the payback period for using an EXAIR Nozzle can be within weeks by the savings in the electrical cost. With the EXAIR products, we were able to partner with Energy Star and power facilities. For the amount of energy savings, some power companies offer rebates for using EXAIR products. We can offer our services to see if your local power company is participating in these rebates.
A substandard blow-off gun is unsafe, loud, waste compressed air, and increase production times. EXAIR Safety Air Guns can help improve these situations in all these areas. They are OSHA compliant, very safe and very quiet. They use less compressed air which saves you money. And with a variety of different nozzles, they can better fit your application to decrease down time. EXAIR offers a 30 day unconditional guarantee on our cataloged items to try. You can see for yourself on how effective these compressed air guns can be. If you need help to match the best Safety Air Gun to your application, you can contact an Application Engineer. And during the next two months, take advantage of the free 1” Flat Super Air Nozzle offer.