Understanding Decibels & Why OSHA Pays Attention to Your Noise Exposure

In the simplest of metric terms, a decibel is one-tenth of a bel.  But, historically, bel was a unit created to honor Alexander Graham Bell who invented the telephone.  In the early days with telephone wires, they noticed that the signal strength would decay over a long distance.  In order to determine power requirements to connect people for communications, they determined that they could use the ratio of power levels.  As a start, it had to be based on a minimum amount of power required for a person to hear on the telephone.  They found that the signal power level to generate an angular frequency of 5000 radians per second would be that minimum value as determined by an average number of people.  They used this mark as a reference point in the ratio of power levels.  Because of the large variations in values, they simplified the equation on a base-10 log scale and dividing the bel unit by 10.  Thus, creating the measurement of decibel.

Today, this same method is used to measure sound.  Like frequency waves that travel through the telephone wires, pressure waves travel through the air as sound.  This sound pressure is what our ears can detect as loudness, and it has a pressure unit of Pascals (Pa).  As an example, a small sound pressure would be like a whisper while a large sound pressure would be like a jet engine.  This is very important to know as high sound pressures, or loudness, can permanently damage our ears.

With sound pressures, we can determine the Sound Pressure Level (SPL) which is measured in decibels (dB).  Similar to the equation for the telephone power signals above, the SPL also uses a ratio of sound pressures in a base-10 logarithmic scale.  For a minimum reference point, an average human can just start to hear a sound pressure at 0.00002 Pa.  So, the equation for measuring sound levels will use this minimum reference point as shown in Equation 1.

Equation 1:

L = 20 * Log10 (p/pref)

where:

L – Sound Pressure Level, dB

p – Sound pressure, Pa

pref – reference sound pressure, 0.00002 Pa

Why is this important to know the decibels?  OSHA created a chart in 29CFR-1910.95(a) that shows the different noise levels with exposure times.  This chart was created to protect the operators from hearing loss in work environments.  If the noise level exceeds the limit, then the operators will have to wear Personal Protection Equipment (PPE), or suffer hearing damage.  EXAIR offers a Sound Level Meter, model 9104, to measure sound levels in decibels.  It comes calibrated to accurately measure the sound to determine if you have a safe work environment.

Sound Level Meter

There is a term that is used when it comes to loud noises, NIHL.  This stands for Noise Induced Hearing Loss.  Once hearing is damaged, it will not come back.  To keep your operators safe and reduce NIHL, EXAIR offers many different types of blow-off products that are designed to decrease noise to a safe level.  So, here’s to Alexander Graham Bell for creating the telephone which can be used to contact EXAIR if you have any questions.

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

 

Photo of Telephone by Alexas_FotosCC0 Create Commons

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

Where:

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

Where:

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.

 

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.

SoundMeter_new_nist225

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
justinicholl@exair.com
@EXAIR_JN

 

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
justinnicholl@exair.com
@EXAIR_JN

 

Where Did All The C Clamps Go?

Over the past week I visited a local company here in Cincinnati that utilized a decent number of flat plastic air nozzles on their production lines.   This style nozzle had been used for many years but were the reason their engineering department contacted EXAIR.   The nozzles they had in place were used in many different applications from ejecting bad parts, holding up box flaps, and even positioning product correctly on the production line.   Every nozzle was tied to a regulator somewhere on the machine and all of the regulators were tuned to different pressures.

The customer was experiencing, at certain points during the day, a pressure drop throughout the entire system that would cause packaging lines to shut down due to low air pressure faults. The customer called EXAIR because they determined the plastic nozzles were using too much compressed air and were also a constant maintenance problem. Primarily, they wanted to see if we had a solution to lower compressed air while still achieving the desired production results.

Being local we were able to visit the customer and after discussing the applications we set out through the manufacturing area to discover if we could offer solutions for the problematic areas. We got about 10′ away from a casing machine and I heard a loud hiss of compressed air.   This was even with my foam ear plugs in.  Once we reached the edge of the machine I was quickly able to trace the sound down to a plastic flat nozzle that had been mounted to the machine, broken and held back in place by a large C clamp like seen below.

IMG_5777.JPG

As we went through the rest of this production line and the rest of the packaging facility, it was clear the customer had settled on using flat plastic nozzles throughout the plant. Generally we see this because the nozzles are cheap – when you forget to consider operating and maintenance costs. This was not the only broken nozzle being held in place by a clamp and it is also the not the only one that was using more compressed air than necessary.

After finishing the tour and performing some tests here in our lab I recommended that they utilize our 1″ Flat Super Air Nozzle with a .005″ thick shim installed.   By installing the 1″ Flat Super Air Nozzle they are going to be able to mount the metal nozzles with minimal modification to their existing setup as well as lower air consumption and noise level. The metal construction makes them more durable and long lasting in an industrial environment. These nozzles will not break when an operator bumps it and the maintenance department will be able to reclaim all the C clamps that are distributed throughout the facility.

Once we have final numbers on how many nozzles have been replaced and what pressures each nozzle is operated at we will provide the customer the air consumption savings as well as the noise level reduction that they are seeing throughout the plant.

Brian Farno
Application Engineer Manager
BrianFarno@EXAIR.com
@EXAIR_BF

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
justinnicholl@exair.com
@EXAIR_JN