Tag: sound level

The Story Behind Decibels

Published on by Russ BowmanLeave a comment

While ‘sound’ has been around (almost quite literally) forever, our units of quantifying it are relatively new. Most of us are familiar with the word ‘decibel’ and know that it has something to do with how ‘loud’ a sound is. The word ‘decibel’ originated, however, as a unit to quantify the loss of the strength of a signal as it traveled through telephone and telegraph wires. From the invention of the telegraph in the 1840’s, miles and miles (and miles) of cable started crisscrossing the country, and eventually the world. The unit they used to quantify signal loss back then was known as a “mile of standard cable” or “MSC”. And it was just that: the loss of signal energy as it traveled through one mile of standard (approximately 19 gauge wire back then) cable.

In 1924, Bell Telephone Laboratories introduced a new unit: the Transmission Unit (TU) which changed the math from linear to logarithmic. One TU was defined such that the number of TUs was ten times the base-10 logarithm of the ratio of measured power to a reference power. In 1928, the Bell folks proposed using a new word they’d coined: ‘decibels’, instead of TU’s, in honor of the founder of their technology and namesake of their company, Alexander Graham Bell.

While the decibel is still the commonly accepted unit of measure for signal loss in cable, it also became popularized as a unit to quantify sound pressure level, since that’s a logarithmic measurement as well, of the ratio of actual sound pressure being applied (determined by the frequency & amplitude of the sound waves hitting your eardrum) to a base level of sound pressure (the low threshold of hearing for a typical person…what we might informally call “complete silence”.)

There are two ways to determine sound pressure level: you can do the math, or you can use a device that measures it, like the EXAIR Model 9104 Digital Sound Level Meter. These will tell us how ‘loud’ a sound (or the overall sound in a given space) is.

In contrast to the 98dBA sound level from this array of nozzles, the sound pressure level from an EXAIR Super Air Knife is only 69dBA.

This is important because too much of ANYTHING is likely to be detrimental, and sound pressure level is absolutely in that category. Exposure to extraordinarily loud sounds, even momentarily, can irreversibly damage your hearing. And constant exposure to moderately loud sound levels can do it too.

In the United States, the Occupational Safety and Health Administration (OSHA) published Standard 1910.95(a) to identify the maximum allowable noise exposure by hours, and sound level. The proper use of hearing protection is mandated if personnel are exposed to levels in excess of these limits for a given period of time:

Working in areas that exceed these levels will require hearing protection.

When I was little, my Dad had to get hearing aids as a result of occupational noise exposure, so I know first-hand what an impact has on one’s quality of life – and that of the people they spend a lot of time around. It’s one of the big reasons that I always talk about how quiet EXAIR engineered compressed air products are, compared with air blowoffs that aren’t designed to attenuate sound pressure levels.

The ability to hear well is a wonderful gift, and one worth preserving. If you have to work in a loud environment, get some good ear plugs or ear muffs. They make them now with noise-canceling features, so you can still hear people talk while wearing them. If you have questions about whether the environment is “too loud”, it very well might be. Take measurements. If they’re higher than the OSHA limits above, consider the source and whether it can be mitigated, or even eliminated. And if the source is from compressed air blow offs, EXAIR can definitely help – give me a call.

Russ Bowman, CCASS

Application Engineer
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Creating a Safer Environment for Industries

Published on by John BallLeave a comment

EXAIR has been at the forefront of safety and efficiency when it comes to blow-off devices since 1983.  We understand the importance of keeping personnel and the workplace safe.  Controlling an employee’s exposure to hazards is a fundamental method of protecting them. The CDC published a useful guide called “Hierarchy of Controls” detailing five types of control methods as a means to implement effective solutions.

  • Elimination
  • Substitution
  • Engineering controls
  • Administrative controls
  • Personal protective equipment (PPE)

Elimination:

Elimination removes the hazard from the source.  Elimination is at the top of the chart because it is the best way to protect workers.  In my previous line of work, we had to use MEK to dilute a solvent-based epoxy.  By switching over to a water-based epoxy, we were able to eliminate the chemical hazard from our process.  In some situations, this can be a difficult task, but the elimination criteria should be the first thing to review.

Substitution:

Substitution is looking for a different but safer modification to the source of the hazard.  An example would be static elimination.  If we take into consideration an ionization bar to remove static, there are manufacturers that make “hot” bars that will shock the operator if they get too close to the ionizing point.  EXAIR Gen4 Ionizing Bars are shockless.  By substituting the “hot” bars with EXAIR Gen4 Ionizing Bars, you just removed the shock hazard for your operators.  When considering substitution, it is important to compare the new risk of the replacement to the original risk.  Remember, we are trying to reduce the potential effects of injuries. 

The CDC explains these first two methods with this statement, “Elimination and substitution can be the most difficult actions to adopt into an existing process. These methods are best used at the design or development stage of a work process, place, or tool.  At the development stage, elimination and substitution may be the simplest and cheapest options.  Another good opportunity to use elimination and substitution is when selecting new equipment or procedures.  Prevention through Design is an approach to proactively including prevention when designing work equipment, tools, operations, and spaces.”1

Engineering Controls:

Engineering controls are very common.  Companies can evaluate an area for hazards and address them with proven controls.  This can be as simple as adding light curtains to a stamping machine.  Another area would be using compressed air for blow-off applications.  EXAIR has been providing engineered products to reduce these hazards.  We offer Safety Air Nozzles, Safety Air Guns, Super Air Knives, and Air Amplifiers to reduce the noise level and dead-end pressure as found in the OSHA directives 29CFR 1910.65(a) for maximum allowable noise exposure and 29CFR 1910.242(b) for dead-end pressure/chip shielding.  By adding an engineered nozzle like our Super Air Nozzle over an open pipe, it will protect your workers, stop OSHA fines, and reduce energy costs. 

Administrative Controls:

These controls will move personnel or change the process to limit the length of exposure time to the hazard.  As you notice, this is toward the bottom of the hierarchy chart as one of the least effective ways for dealing with a hazard.  As an example, an operator is exposed to a blow-off application that has a noise level of 95 dBA.  The maximum exposure time allowed by OSHA is 4 hours.  So, another operator would have to be placed in that area to work another 4 hours.  But, if the company added a Super Air Nozzle to the blow-off device, then the noise level would be reduced to 74 dBA.  Now, you can have one operator run the machine for the full 8 hours.  

PPE:

Personal Protection Equipment, or PPE, is equipment that is purchased to help protect the operators from hazards.  What may the problem be?  First, you have to train the operators on how to properly use them, as well as trust that they will follow the instructions explicitly.  It also adds cost to purchase and maintain them.  This is why this method is the least effective. 

At EXAIR, we have a statement: “Safety is everyone’s responsibility.”  The idea behind the NOSH hierarchy is to help review hazardous areas and implement safer products.  EXAIR can help your company follow the Hierarchy of Controls, to eliminate or reduce the hazards of compressed air usage.  Many EXAIR products, including Super Air Knives, Super Air Nozzles, Safety Air Guns, and Air Amplifiers are engineered to meet OSHA standards. If you have questions or want to talk to an EXAIR Application Engineer, please contact us to discuss how our products will be beneficial to your work environment’s safety. 

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

Note 1: https://www.cdc.gov/niosh/topics/hierarchy/default.html

Picture:  Safety First by Succo.  Pixabay License

What is Sound, and How Can You Reduce It?

Published on by John BallLeave a comment

Many manufacturing plants have a strong focus on safety for their workers.  One major safety concern that is commonly overlooked is noise.   Occupational Safety and Health Administration, or OSHA, has a directive that defines the noise exposure over a time-weighted average; 29CFR 1910.95(a).   For an eight-hour day, the maximum noise level is 90 dBA.  The Center for Disease Control, CDC, reports that “approximately 18% of all manufacturing workers have hearing difficulty”1.

What is sound?  In the simplest of terms, a decibel is one-tenth of a bel.  Historically, bel was a unit created to honor Alexander Graham Bell, who invented the telephone.  Like the frequency waves that travel through telephone wires, pressure waves travel through the air as sound.  This sound pressure is what our ears can detect as loudness.  EXAIR offers a Digital Sound Level Meter, model 9104, that is calibrated and can measure sound in decibels.  It is very important to know the sound level, as it can permanently damage your ears.

Here is a test for you.  If you go and stand in your plant, you can probably hear loud noises coming from your compressed air system.  EXAIR has an engineered product to solve most of them.  On the Hierarchy of Controls for NIOSH, Personal Protection Equipment, PPE, is the least effective.  A better control would be to isolate your operators from the hazard with an engineered product.  EXAIR can offer that solution for many of your blow-offs and pneumatic discharges to reduce noise levels.  This would include; but not be limited to; Super Air Nozzles, Safety Air Guns, Super Air Knives, and Super Air Amplifiers. 

Let’s look at a ¼” open copper tube.  It can create a sound level of over 100 dBA.  They are commonly used because they are readily available and inexpensive to make.  But they waste a lot of compressed air, as well as creating a hazard for your operators.  Just by adding a model 1100 Super Air Nozzle to the end of the copper tube, we can reduce the noise level to 74 dBA at 80 PSIG (5.5 bar).  Wow!  Not only will it remove the hazard, but it will reduce the amount of compressed air usage; saving you money.  Here is a quick video to show the importance of the EXAIR Super Air Nozzles.

At EXAIR, we have a statement, “Safety is everyone’s responsibility.”  EXAIR manufactures engineered products with high quality, safety, and efficiency in mind.  To keep your operators safe, 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 you can use to contact an Application Engineer at EXAIR.  We will be happy to help to reduce your sound levels. 

John Ball
Application Engineer


Email: johnball@exair.com
Twitter: @EXAIR_jb

Note 1: https://www.cdc.gov/niosh/topics/ohl/manufacturing.html

OSHA 1910.95(a) Explained: Occupational Sound Exposure

Published on by Tyler DanielLeave a comment

Hearing loss due to high noise levels is a common problem in many industrial facilities. Without the use of proper PPE, hearing loss can occur quickly. This is a serious concern as hearing loss is permanent and once the damage is done there’s no way to reverse it. Due to this risk, OSHA strictly enforces standard 29 CFR-1910.95(a).

This directive discusses the effects of noise and limits exposure based on the dBA. The table below indicates the maximum allowable exposure time to different noise levels. Sound levels that exceed these levels should first be addressed by proper engineering controls such as isolating the source of the sound from personnel or replacing the cause of the sound with something like an engineered compressed air nozzle. When such controls aren’t feasible, proper PPE must be worn to protect the operator.

Hearing loss can occur in as little as 30 minutes when exposed to sound levels 110 dBA or greater. Operators have a tendency not to use PPE as directed, if an OSHA inspector comes to your facility and notices that the sound levels exceed the maximum allowable level without protection hefty fines will be soon to follow. In this example from the United States Department of Labor, a company was fined a total of $143,000 for failing to protect their employees.

In order to identify the places or processes in your facility that are causing the problems, you’ll need a tool to measure the sound level. EXAIR’s easy to use Digital Sound Level Meter allows you to measure and monitor the sound level pressure in a wide variety of industrial environments. The source of the loud noise can then be identified and isolated so that corrective action can be taken. For compressed air related noise, EXAIR manufactures a wide variety of engineered compressed air products that can reduce the sound level dramatically. In many cases, EXAIR products are capable of reducing noise levels by as much as 10 dBA. Since the dBA scale is logarithmic, this equates to cutting the sound level in half!

If there are processes within your facility that are above these limits, and you’d like to eliminate relying on proper PPE, give an Application Engineer a call. We’ll help walk you through the selection process and make sure that when the OSHA inspector comes knocking you’re prepared!

Tyler Daniel, CCASS

Application Engineer
E-mail: TylerDaniel@exair.com
Twitter: @EXAIR_TD