NOISE:
What is NOISE?
- Unwanted SOUND. OSHA considers an 8 hour time-weighted average noise exposure of 85 decibels to be too loud.
Noise Induced Hearing Loss
- Partial or complete hearing loss in one or both ears
- Cumulative, permanent loss of hearing that develops gradually after months or years of exposure to high levels of noise
- Can arise from traumatic injury (explosions)
- In most cases is irreversible
Decibel
- The unit used to express the intensity of sound.
- dBA – abbreviation for decibels, “A” scale. “A” scale approximates human hearing.
What NOISE levels are safe?
- Depends upon time of exposure
- Below are the OSHA standards for noise exposure when you are wearing no hearing protection. What this means is if your noise exposure is 94 dBA, you can theoretically stay in that exposure for 1 hour and not hurt your hearing.
| 85 dB | 88 dB | 91 dB | 94 dB | 97 dB | 100 dB | 103 dB | 106 dB | 109 dB | 112 dB |
| 8 hours | 4 hours | 2 hours | 1 hour | 30 min | 15 min | 7.5 min | < 4 min | < 2 min | < 1 min |
- A good rule of thumb: If you have difficulty hearing someone standing 5 feet away talk, then the noise level is too loud. You should be wearing hearing protection.
- Hearing loss is usually slow to occur so you will not notice it until it is too late!
- Glass grinders, wet belt sanders, torches, glory holes, compressors and drills are sources of significant noise exposure (often greater than 100 decibels)
| The Ear
Any source of sound sends vibrations or sound waves into the air. These funnel through the ear opening, down the ear canal, and strike the eardrum, causing it to vibrate. The vibrations are passed to the small bones of the middle ear (ossicles), which transmit them to the hearing nerve in the inner ear. Here, pressure changes cause hair cells to move which become nerve impulses that go directly to the brain, which interprets the impulses as sound. Excessive noise can permanently damage the hair cells causing noise induced hearing loss. |
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- Noise induced hearing loss can not be cured, but it can be stopped by reducing noise exposure!
- If you think you have experienced a hearing loss, go to an audiologist for a hearing test!
- Always wear Hearing Protection whenever you are using a noisy piece of equipment!
Hearing Protection:
| Ear Plugs Claimed noise reductions up to 30 decibels
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Compressible foam
Non-Compressible foam (reusable)
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| Ear Muffs Claimed noise reductions up to 25 decibels
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How effective is Hearing Protection?
- NRR (Noise Reduction Rating)
- NRR ranges from 10 - 30 decibels
- Listed on the package
- Estimate of expected noise reduction
- Conducted in a laboratory under ideal conditions
- Not an accurate estimate of actual noise reduction
| 7 dB correction: | Measured Noise Level: | 100 dB |
| Manufacturer's claimed NRR: | - 26 dB | |
| Safety Correction: | - 7 dB | |
| Actual Noise Attenuation: | 19 dB | |
| Actual Decibel Exposure: | 81 dB | |
| Actual Decibel Exposure = 100 dB - (26-7) = 81 dB | ||
| 7 dB correction + 50%: | Measured Noise Level: | 100 dB |
| Manufacturer's claimed NRR: | - 26 dB | |
| Safety Correction: | - 7 dB | |
| Actual Noise Attenuation: | 19 dB | |
| OSHA recommended 50% correction: | 19 dB X 50% = 9.5 dB | |
| Actual Decibel Exposure: | 90.5 dB | |
| Actual Decibel Exposure = 100 dB - (26-7)X50% = 90.5 dB | ||
REMEMBER! You want to keep your Time-Weighted Average noise exposure to < 85 dB!
Wear hearing
protection that fits you well, is comfortable and has the highest
NRR. In reality, unless
you are working around high levels of noise all day, the 7 dB Safety
Correction is probably adequate.
Sources of heat:
- Hot work with a kiln (combing)
- Torch
- Glory Hole
- Furnace
Heat Illness can start when temperatures get above 80 degrees! High humidity can make things worse!
What problems can be caused by excessive heat?
- Heat Cramps: Cramping of muscles and stomach. Caused by heat and electrolyte deficiency
- Heat Stress: Profuse sweating, dizziness, fatigue.
- Heat Exhaustion: No sweating (thermoregulatory system shuts down), possibly fatal!
How do you prevent Heat Illness?
- Stay properly hydrated
- Drinks lots of water
- Maintain electrolyte balance (there are electrolyte replacement fluids such as Gatoraide)
- Maintain proper diet
- Avoid Alcohol - Dehydrates the body
- Get plenty of rest
- Allow plenty of breaks in a cool area!
- Do NOT use salt pills!
Acclimatization
- If you are going to be working in a hot environment for several weeks, start slow and give your body time to get used to the heat
- Use Common Sense! Do you really have to blow glass in your studio in Florida in the summer????????
How to protect yourself working around an open kiln:
- Follow the heat illness guidelines
- Wear reflective (aluminized) garments
- Wear a face shield
- Wear eye protection
- Infrared (IR) is the frequency of most concern to kiln glass artists.
- Occurs whenever there is radiant heat (glowing)
- Eyes are most affected
- IR is absorbed by iris, cornea, lens
- Can result in: “Dry Eye” or “Glassblower’s Cataracts” with high, long term exposure
- Goal is to minimize IR transmission
- Protection:
| ANSI Shade | IR Transmission | Visible Transmission | |
| 1.7 | 15% | 56% | |
| 2.0 | 10% | 39% | |
| 2.5 | 3% | 23% | |
| Didymium | 67% | 63% | Not recommended for kiln! Torches only! |
Remember - the goal is to minimize IR transmission, so the LESS the IR transmission, the better. However there is a trade-off. Decreased IR transmission means decreased visible light transmission:
- A periodic “peek” in the kiln is not a problem
- The main exposure risk is viewing > 1 minute at a time
- Recommendations: AUR-99 (ANSI shade 1.7, 2.0, 2.5) www.auralens.net
