Sound level Dosimeter readings from the shop

[John Pratt]

Previously I posted the sound level readings from many of the different tools around the shop using a dosimeter reading dBA for for those different tools. See: http://www.sawmillcreek.org/showthread.php?200942-Noise-level-readings-in-the-shop

I promised to report the findings of the most recent readings from wearing a personal dosimeter around the shop for three days for those who might find it intriguing in the interest of hearing conservation.

Caveat: I am not a hearing conservation specialist. The reading and numbers listed below are how the hearing conservationist expliained them to me.

NOTES:
1. All reading are weighted on the "A" scale.
2. The criterion noise level (maximum allowable accumulated noise exposure) measured using the OSHA hearing conservation amendment action level of 85dBA for 8 hours
3. LAVG = Average sound level measured over the run time
4. TWA = Time weighted average (figuring an 8 hour run time)
5. Location peak reading = highest reading during the time measured
6. Dose level = using the OSHA criterion level
7. Projected dose = figuring that the noise levels are experienced for a full 8 hour period.


Day 1:
Time measured - 6 hours
LAVG - 92.9dBA
TWA - 91.7dBA
Location peak reading - 141.2dBA
dose level - 473.3%
projected dose - 622.9%

Day 2:
Time measured - 6 hours
LAVG - 84.4dBA
TWA - 82.9dBA
Location peak reading - 134.2dBA
Dose level - 62.4%
Projected dose - 88.4%

Day 3:
Time measured - 6 hours
LAVG - 83.6dBA
TWA - 82.2dBA
Location peak reading - 125.8dBA
Dose level - 53.3%
Projected dose - 74.1%

Overall assessment: WEAR HEARING PROTECTION!!

[Don Orr]

John-thanks very much for your post. I find it very interesting. I DO wear hearing protection as much as I can. Sometimes I forget to take it off when doing quieter work. I had a friend stop by to my shop once and he made a funny face. I was hand planing a board with my earmuffs still on!

Were these measurements done in your home shop?

[Jim Koepke]

Not being one to enjoy wearing ear protection is just one of my reasons for not using noisy tailed tools.

Biggest noise in my shop is when the mallet hits a mortising chisel.

jtk

[John Pratt]

Were these measurements done in your home shop?

These reading were done at my work shop (which for all practical purposes is the same as my home shop. Same tools and I am still the only one doing the work).

[Larry Frank]

What tools gave the high dB readings? How close to the high levels were you?

The 141 db is really high as are the other two high readings for other days. The previous readings that you posted were not even close to the highs you measured on the three days.

[Michael Dunn]

I seriously question that 141dB. 130dB is the threshold of pain. Instantaneous irreparable hearing damage occurs then.

[John Pratt]

It is hard to say which machine at exactly which moment gave the high readings. The whole point was to see what the average noise exposures were during the course of an average work day. My guess is it was either the CNC machine or the compound mitersaw. You can't just take into account the tool itself because there are other tools/items making noise at the same time (i.e. dust colletion, radio, and the CNC obviously runs while I am doing other things). The high readings may only last for a short period, but the dosimeter reads them as the peak level experienced.

The numbers provided were the readings experienced in my shop and yours may obviously vary.

For those that doubt the readings; they were taken with a professional dosimeter worn on the right collar of the shirt near the ears, analyized by professional technicians from the audiology department of a large military hospital. They are quite proficient in this area since hearing loss is (now) a major concern for military members and DA civilians. The readings are provided here for information purposes only and if you disagree with them you are free to disregard and provide your own readings and experiences.

130dBA is the normal threshhold for pain, but that doesn't necessarily mean you experienced pain for that shockwave of sound. A gunshot from an army rifle may be as high as 150-170dBA but it is only after repeated shots that a person may experience "pain". Of course, "pain" is subjective. A more apt comparison would be the noise when wood falls off your wood rack in the shop or some similar short burst of noise in in the shop. it is instantaneous and short lived, but the dBA reading of that event may be quite high. I don't experience "pain" during these events because I wear hearing protection throughout the shop when tools are running. I lost enough hearing during my 24 years in the Infantry that I don't need to lose any more.

[Larry Frank]

I am not questioning the equipment of the interpretation.

However, 141 db is incredibly loud. If it where me, I would want to understand what is producing a noise that loud and dangerous and do something mitigate the sound. Even with hearing protection, sounds that loud can be damaging.

[Ole Anderson]

Is it possible the mic of the dosimeter got bumped?