OSHA's Noise Exposure Regulations

Factual Questions
1

I’ve always been interested in monitoring sound level meters and seeing how loud things are. I’ve done a lot of research in this topic and know quite a lot about how loud things are.

I also own a Digital Sound Level Meter from AZ Instruments - - YouTube

I really like this sound level meter due to its auto-ranging function.

My old one used to be so over-sensitive and cheap, so I got this one as it’s considered to be a much more fine device (probably still not professional but the professional ones can cost over $600, and this is considered to have specs that you normally won’t find on cheap sound level meters).

Lately, I’ve been questioning OSHA’s regulations and wondering if they are REALLY that reliable.

For those of you that are not familiar, OSHA’s regulations regarding noise exposure are:

90 dBA - No more than 8 hours per day
95 dBA - No more than 4 hours per day
100 dBA - No more than 2 hours per day
105 dBA - No more than 1 hour per day
110 dBA - No more than 30 minutes per day
(…I’m sure you can see the patern)
140 dBA - No exposure (as loud as a jet engine at 100 feet)

Now, I own the Samsung Galaxy Nexus. I plugged in some ear buds and set the equalizer and the volume settings to the maximum, and it was pretty freaking loud. My sound level meter said 105 dBA. That made me question, can I really safely listen to music that loud for an HOUR a day (note that I probably wouldn’t want to)?

Today, I’m going to test my dad’s car speakers at maximum volume. He has great speakers in that car, ones that costed I think around $300 to install. It’s pretty good performance. It maintains its clarity, and I turned the speakers about a half way up and it already reached 85 dBA, so I’m going to test what it would be, all the way up!

But what I’m wondering about is whether or not I can really rely on OSHA’s regulations.

Because, it you follow its pattern, it’s like saying that your ears can withstand 85 dBA for 16 hours a day without receiving any damage, and that sounds like a dubious statement since 85 dBA is quite loud. It’s the equivalent of someone yelling really loudly right in front of your face. Do you really think that your ears could withstand that for 16 hours a day? I don’t know, but something seems fishy about OSHA’s regulations.

2

As far as I am aware OSHA does not have jurisdiction over sole proprietorships or other companies where no employer-employee relationship exists. This is not even a worksite related issue - unless you are saying that phone operators are forced to use the Samsung phone you mentioned.

Here is a good article on phone operators hearing tests - link - The effects of noise on telephone operators - PubMed

Also - have you verified that the sound meter you have is measuring a time averaged noise level and instantaneous peaks ?

3

How did you measure the sound level from the ear buds? A meter like that is designed for free field noise measurements (out in an open space). If you are just holding it up to the ear buds I don’t believe that is a direct comparison to something measured in an open space like the OSHA regs are designed to be. There are probably special tools for measuring sound level of things like headphones and and telephones etc.

4

It was set on slow response which was measuring a time averaged noise level. I went in my dad’s car that has great speakers (as mentioned in the OP), maxed out the volumes, and still only came out to 88 - 92 dBA, which seems surprising. It was VERY loud. It was turned up to the point where my body was starting to perceive vibrations (I was in there for less in a minute so no damage implied), and my dad said he could hear it loudly, inside the house on the second floor. The car was in a closed two-car garage.

Now, according to OSHA, I can listen to that inside the car for 8 hours! Something looks fishy to me about that… Can I really (Of course, I probably don’t want to, but just wondering as a “can” question)?

5

Are the OSHA regulations for exposure to bare-eardrums, or for workers with hearing protection worn? That might explain any discrepancy.

6

You need to look up industry-specific OSHA regulations. Depending on the level of noise exposure known in the studied industry, there will be recommendations as to what ear protection is needed, from simple foam inserts to the plastic kind to the headphone-style muffs.

7

I wonder if your meter is not reading low. From the noise level charts I have seen ~90 dB should be loud but not THAT loud, similar to pushing a lawn mower. You shouldn’t start to feel your chest vibrating until you are above 110 db, which is also the level that would seem more typical for a maxed out, high-end car stereo.

Regardless, it is interesting to note that the NIOSH recommendations are a bit more conservative than OSHA’s. They recommend hearing protection for a 8-hour TWA above 85 dB and halve that time for every 3 dB increase rather than 5 dB as OSHA does.

8

Live sound engineer here,

DB meters are generally designed to use in a somewhat open space, you may well be skewing the results buy having closed the car doors or placing the earbuds too close.

IME 90 db is about minimum for music to be heard by a reasonably quiet audience, 97/98 to be heard, 102 is loud, 107 too loud. I have been louder, I don’t like it much. Every 10 db is a perceived doubling of volume, actually sound pressure level SPL. OSHA regs IMHO are not too far from realistic, I have serious hearing loss after being around loud PA systems for 26 years. I wish I knew about earplugs when I was a teen playing in bars, I cannot hear above 14k or around a corner.

Capt

9

I think your readings are artificially high. To those that don’t know, the decibel scale is logarithmic so small jumps in numbers are many times higher than lower ones. That said, I work as an engineer in a factory environment and it can be quite loud when everything is running but we are fairly fairly quiet as far as factories go.

Hearing protection is available for anyone that wants it but nobody uses it past the first day. You simply get used to it even though you probably will suffer some small degree of low-level hearing loss after years of exposure but you don’t get ringing in your ears like you do from loud music or gunshots… It passes OSHA regulations and gets checked regularly.

However, it doesn’t sound nearly as loud as a pumped up car stereo system or a rock concert. Nobody could listen to that all day for years. We are more worried about bursts of extreme sound that cause energy peaks.

10

Try the C reading in the car. The chest-thumping bass, which is contributing a lot to your sense of loudness, isn’t registered on the A weighting, but is on the C.

To put it simply, the A weighting is for the speech band; C is for music. It’s too bad that regs are all based on A, but that does make sense since it’s where the damage does the most damage. That is, being unable to hear speech clearly is worse than being unable to hear deep bass or high treble, from a practical standpoint. Also, I beleve the ear is more prone to damage in the A range than the low end of the C range. (The high end of the C range, well, we lose that no matter what!)

As a musician, if stage levels go over 110 dB SPL© for anything but occasional crescendos, I’m out of the band. That’s really bloody loud. However, when I go to venues where younger folks like to haunt, those large standing-only venues that have regional and smaller national acts, I’m dismayed to see that many of them run over 110 dB SPL© to the audience. I’m glad I have good earplugs. It’s ridiculous to run that loud, but that sure seems to be popular.

I did all my measurements with a $40 Radio Shack analog meter, but I’m confident the readings were reasonably accurate. It’s not rocket science.

11

I see several problems with what you are doing. First is the already mentioned use of A weighting for your measurements. I work in OE automotive audio, and we don’t use any official “weighting” at all. Second, you’re measuring a single point in the car, and that’s problematic because a car interior is a closed pressure field with nodes and anti-nodes at various frequencies based on the dimensions. so if you put the microphone in a location where there’s a node, you’ll measure low. as a reference point, with my equipment, the factory system in my Mustang GT measures 112 dB max broadband SPL.

that’s not a valid measurement because- just like a car interior- when you stick the earbuds in your ears, they are now playing into a (mostly) closed pressure field- i.e. your ear canal. When I did some testing of earbuds to whatever EU standard dictates the maximum possible loudness, I had to use a HATS with specific occluded ear simulators.

12

It’s interesting to note that the sound intensity (and therefore the damage done to your hearing) doubles every 3 dB, yet the OSHA standards halve the duration of exposure every 5 dB. That’s absurd.

13

The presumption here seems to be that OSHA dictates “safe” exposure levels. Is this accurate?

I was under the impression that OSHA dictated “acceptable” exposure levels.
In other words it is unlikely you will suffer immediate or debilitating hearing loss, but you might have long term effects not deemed debilitating. YMMV

14

Actually, I think OSHA dictates “unsafe” levels. That is, go over this limit, and it’s bad. Not allowed. Allowed doesn’t necessarily imply safe for everyone. Just a tolerable failure level.

For years, divers used decompression charts created by the US Navy. Well, those charts were for fit young men, with an acceptable 5% failure rate (in how many dives I don’t remember). Before long, the folks making the rules for recreational divers realized we need a wider safety margin thanks to all the overweight 50 yr olds, etc.

The point being, any “safety level” is based on some quantifiable failure criteria, which isn’t 0%. No idea what OSHA’s is, but you never reach 0% so that’s not it.

15

Well, I thought that they say, “Use A-weighting for OSHA related applications.” That’s what I’m doing. OSHA has requirements for what you can and cannot be exposed to, so I thought it would be most effective to use A-weighting. And I only have A/C weighting so I do have to use SOME weighting. As for the direction of the microphone, what do you recommend I do? How should I go about measuring my car’s audio system in terms of how it comply’s with OSHA’s regulations?

88 - 92 dBA in a maxed out car audio system is artificially high?

I don’t know. I’ve heard of NIOSH many times, and honestly, this is another question I had. Which one should I follow, NIOSH or OSHA? This has always been an unsolved confusion for me because they’re so different. OSHA believes that you can tolerate 120 dBA for 7.5 minutes, and NIOSH only says ~0.12 minutes!

Really? I thought it was every 10 dBA you increase, you’re doubling the sound pressure level. That’s what I read.

16

Ok, maybe I need to re-read your OP, but I have to ask why you’re concerned about a car audio system complying with OSHA requirements when it’s not subject to them? Is it just so you can use it as a reference to gauge how loud something is?

I guess another part of the issue is if you’re measuring the car by blasting music at maximum volume. Music is far too varying a signal for a typical SPL meter to give you a worthwhile reading. You need a more controlled signal like pink noise, in concert with a long averaging time.

it’s more like people in general will perceive a 10 dB increase as “twice as loud,” even though in reality the sound power doubles every 3 dB.

17

OSHA link. Measurement of 85 dBA over 8 hours are what triggers the OSHA warnings, etc. I don’t know the technical details of how they do the measurement but this is measured without any filtering.

18

Well, I’ll weight it A and C. I’m going to do one more test. But the reason I was using “A” was to reference how loud it felt, and then see how that compares with OSHA. You see, I thought “A” frequency was to see how the human ear responds, so I wanted to see how many decibels a human ear would perceive it as so that then I can reference it on the OSHA chart.

I’ll weight it C, so that I can actually have a number that I can “brag” about (well, not brag, but when testing performance, it’s a good idea to put it in C to eliminate that weighting curve.)

I was wondering if maybe I could get a “pink noise” app on my phone, and then plug that in to my car audio system. That would be good for performance purposes.

It’s a little hard to explain, but like I said above, I’m also trying to reference my dad’s car audio system to OSHA’s standards and “how loud” the music is. Like if you went to a night club to measure this (you probably wouldn’t), and you wanted to see how loud you could listen to music “that loud” for, then I would assume that you would set it to “A”. That’s the kind of thing I’m implying with my car audio system if that helps explain it better. Now, I have a feeling that for this kind of application, it would be better to actually play music because that’s what you actually listen to, and if I’m trying to compare the “A” reading to the OSHA regulations to see how long I can listen to it, then wouldn’t you want to play actual music? (That part is a little hard to explain)

As far as, angling my meter right, how should I do it? Should I stick it up to the ceiling, or should I point it towards one of the speakers or place it in the shape of my ears (this is for when I’m measuring for health and safety concerns, or “A” frequency weighting).

And how should I angle it when I’m in “C”?

19

A week and a half did it for me.

20

10 log(P2/P1) = 10 log(2) = 3 dB

An increase of 10 dB is equivalent to a increase in the sound pressure level by a factor of 10.