Safe listening levels and Exposure to SPL? - AVS Forum
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post #1 of 20 Old 06-16-2014, 02:33 PM - Thread Starter
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Safe listening levels and Exposure to SPL?

Hi everyone, I have a question, say I were to watch a movie at -15db (0db being reference) with the LFE channel 10db "hot" would there be a way of estimating the average SPL I was exposed to over the length of the movie?.

I suppose one could record the movie with a Mic and laptop and average the SPL? and I understand that different movies would have different averages of SPL (heavy LFE tracks having more total SPL for example).

The reason I ask is because I feel I have some minor "noise induced hearing loss", I love the tactile feeling of low bass, but obviously my hearing health long term is very important.

I find it difficult to hear conversations in noisy environments, and I know that NIHL affects the "vocal" frequencies first, a sort of "notch" in the frequency response of the ear.

So if anyone has information or thoughts on the matter It would be great to hear them.

John.
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post #2 of 20 Old 06-16-2014, 02:38 PM
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There are much louder levels of sound than a movie theater and especially constant sounds. I would think your problems are from everyday life. There are other threads with great info about this.
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post #3 of 20 Old 06-16-2014, 02:55 PM - Thread Starter
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Well, I only developed the problem in the last few years after I built my Subs and started watching movies at a much louder level. Also, I always use hearing protection with day-day life and rarely go to Clubs/Bars that play loud music. I am just trying to figure out the total level and duration of SPL I am exposed to while watching a film, so I know it is safe.
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post #4 of 20 Old 06-16-2014, 03:38 PM
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Well, the levels you stated are for what frequencies? The LFE? The guidelines are for higher frequencies so the lower frequencies are a crap shoot. I listen much louder than you and have no problems, it has to be something else. People lose the hearing as they age, how old are you? You say you wear hearing protection, from what?
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post #5 of 20 Old 06-16-2014, 03:43 PM
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Well, I only developed the problem in the last few years after I built my Subs and started watching movies at a much louder level.
How old are you? Hearing acuity declines with age. It's the third thing to go. Memory is the second. I forget what the first is.

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post #6 of 20 Old 06-16-2014, 05:02 PM - Thread Starter
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Haha, well I am only 28 and my higher frequency hearing is fine. I am merely saying that I have some symptoms of NIHL, and I feel its from watching films at levels that were too loud with my home theater system (Its capable of 130db peaks, the subs are twelve 12's (ported) with 3.3Kw power input in a 1,800 cubic foot sealed room).

Just because you listen to higher levels with no apparent problems does not mean that I have not damaged my hearing in recent years, after all, the anatomy of everyone's ears is going to be slightly different. Also is it not the case that the ear is simply more sensitive at mid frequencies (Intelligibility) and that bass frequencies are still capable of damaging the ossicles and other workings of the inner ear?.

I am not trying to start an argument about weather we listen to films at too high SPL levels's, I am just trying to determine what are safe levels to listen at.

I use hearing protection for cutting the grass, power tools etc. I am not in a loud working environment day to day.
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post #7 of 20 Old 06-16-2014, 05:08 PM
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I just want to see a pic of 12 12's...
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post #8 of 20 Old 06-16-2014, 05:26 PM
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Also is it not the case that the ear is simply more sensitive at mid frequencies (Intelligibility) and that bass frequencies are still capable of damaging the ossicles and other workings of the inner ear?
Damaging frequencies closely follow equal loudness curves, so we are far less likely to suffer damage from lows or highs as we are the midrange. Exposure to 105-110dB broadband for a couple of hours a day shouldn't be a problem. That's plenty loud enough for any sane person. But of course that means that at 28 you've only recently arrived at that milestone.

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post #9 of 20 Old 06-16-2014, 05:41 PM
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For frequencies above 100hz, the recommended-max average-level works out to be ~90dbA for a 1-2 hour movie.

It is really the mids and tweets that kill your ears far faster than bass.
If you are experiencing hearing loss I would keep the speakers to the lowest level that you can get away with while still being able to hear what is being said, and no louder.

For bass, anything more than 105db is probably starting to get unsafe; and surely by 115db.

The environment can really make a large difference too.
If you live under an airport besides a train, work as a miner, go to the club every weekend, and have a hobby of wood-working and target practice and grass cutting, then you will (likely) be 100% deaf in no time.


Knees, spine, eyes, ears, memory... you gotta LOVE getting OLD!!!
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post #10 of 20 Old 06-16-2014, 05:53 PM
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Originally Posted by homeboydeluxe View Post
Also is it not the case that the ear is simply more sensitive at mid frequencies (Intelligibility) and that bass frequencies are still capable of damaging the ossicles and other workings of the inner ear?
Damaging frequencies closely follow equal loudness curves, so we are far less likely to suffer damage from lows or highs as we are the midrange. Exposure to 105-110dB broadband for a couple of hours a day shouldn't be a problem. That's plenty loud enough for any sane person. But of course that means that at 28 you've only recently arrived at that milestone.
Yikes! IMO, 105-110 dBA is WAY too much for two hours. OSHA specifies 90 dBA average over eight hours, and for each 5 dB above that, cut the exposure in half. So that would put the "safe" exposure at 105 dBA at one hour and 110 dBA at 30 minutes. However, I believe that the OSHA standards are way too liberal for real safety. Here's a quote from the OSHA website:

"OSHA sets legal limits on noise exposure in the workplace. These limits are based on a worker's time weighted average over an 8 hour day. With noise, OSHA's permissible exposure limit (PEL) is 90 dBA for all workers for an 8 hour day. The OSHA standard uses a 5 dBA exchange rate. This means that when the noise level is increased by 5 dBA, the amount of time a person can be exposed to a certain noise level to receive the same dose is cut in half.

"The National Institute for Occupational Safety and Health (NIOSH) has recommended that all worker exposures to noise should be controlled below a level equivalent to 85 dBA for eight hours to minimize occupational noise induced hearing loss. NIOSH has found that significant noise-induced hearing loss occurs at the exposure levels equivalent to the OSHA PEL based on updated information obtained from literature reviews. NIOSH also recommends a 3 dBA exchange rate so that every increase by 3 dBA doubles the amount of the noise and halves the recommended amount of exposure time.

"Here's an example: OSHA allows 8 hours of exposure to 90 dBA but only 2 hours of exposure to 100 dBA sound levels. NIOSH would recommend limiting the 8 hour exposure to less than 85 dBA. At 100 dBA, NIOSH recommends less than 15 minutes of exposure per day."

I'm with NIOSH on this one!

Bill is correct that noise-induced hearing loss normally affects the midrange (2-4 kHz), which is exactly where speech consonants live. This is why it's more difficult to understand conversations in a noisy environment. Plus, NIHL is cumulative and insidious; it often doesn't manifest until years after the exposure, when it's too late.

As for measuring the levels in your theater, I use the AudioTools iPhone app from Studio Six Digital. The app is $20, and to get a realistic measurement over time, it's best to use the add-on called SPL Graph, which is another $6. I also sprung for the calibrated microphone, which is $200. That's pretty expensive, but as a professional in this field, I felt it was a worthwhile investment. You can probably do without the microphone, but the iPhone's internal mic overloads somehwere around 100 dBA or so. I think Android phones do much better in this regard, but I don't know what SPL apps are available for it.

For more about hearing protection, loss, and compensation for loss, please watch my Home Theater Geeks podcast episode 209 here.
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post #11 of 20 Old 06-16-2014, 08:22 PM
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Yikes! IMO, 105-110 dBA is WAY too much for two hours.
"Here's an example: OSHA allows 8 hours of exposure to 90 dBA but only 2 hours of exposure to 100 dBA sound levels.
OSHA standards are measured dBA. They're useless with respect to full range material, be it music or HT. Music measured on the dBC scale will come in about 10dB higher than when measured dBA, while HT measured flat will come in at least 15dB higher than when measured on the dBA scale. In other words, with music add 10dB to the OSHA spec, with HT add 15dB.

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post #12 of 20 Old 06-17-2014, 12:14 AM
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OSHA standards are measured dBA. They're useless with respect to full range material, be it music or HT. Music measured on the dBC scale will come in about 10dB higher than when measured dBA, while HT measured flat will come in at least 15dB higher than when measured on the dBA scale. In other words, with music add 10dB to the OSHA spec, with HT add 15dB.
Ah, so you were specifying dBC, then? You're right about the differences between dBA and dBC, but even compensating for the difference, I would still follow the NIOSH recommendations rather than OSHA.

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post #13 of 20 Old 06-17-2014, 02:09 AM - Thread Starter
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Originally Posted by

For more about hearing protection, loss, and compensation for loss, please watch my [URL="http://www.avsforum.com/forum/138-avs-forum-podcasts/1534730-importance-hearing.html"
Home Theater Geeks podcast episode 209 here[/URL].
Hi Scott, your video on NIHL is exactly why I posted about this topic! Its very in depth and informative!, I love the home theater geeks show, only stumbled upon it a few months ago, and am hooked since.

I have a Behringer ECM-8000, so if I can get that app (Or REW?) you mentioned (or something similar for Android) and record the levels of a few films at listening position using db(C) and average it, then I can get my answer Hopefully!.

Thanks for everyone's input so far.
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post #14 of 20 Old 06-17-2014, 02:21 AM - Thread Starter
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Here is a link, and short description of the setup and a video of a sine wave sweep:

http://www.avforums.com/threads/twel...power.1473809/

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post #15 of 20 Old 06-17-2014, 06:59 AM
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Ah, so you were specifying dBC, then?
Of course. If you measure using dBA you're effectively excluding all content below 200Hz, making it useless with music and HT. If you look at a dbA chart you'll see it's -10dB at 200Hz, -20dB at 100Hz, -50dB at 20Hz.

Ten years ago a large concert venue near me had massive noise complaint issues, and were on the verge of being shut down because of them. At the heart of the issue was the bass. This, after they paid a consulting firm $25k to do a study, create a community noise standard, and install a computerized system in the FOH that warned when the standard was being exceeded. Despite the fact that the standard was not exceeded the complaints continued.
Then they hired me to fix it. It took me all of 30 seconds to find the problem: the level standard and the FOH measuring system were dBA. The bass wasn't even being measured. The clueless consulting firm they'd hired had pissed away $25k, because they followed OSHA standards for industrial noise.

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post #16 of 20 Old 06-17-2014, 07:49 AM
 
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If you watch a movie at reference, won't the average level the movie will be played at be around 90-95 dB? Which is perfectly fine for 2 hours.
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post #17 of 20 Old 06-17-2014, 08:22 AM
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Quote:
Originally Posted by Bill Fitzmaurice View Post
Of course. If you measure using dBA you're effectively excluding all content below 200Hz, making it useless with music and HT. If you look at a dbA chart you'll see it's -10dB at 200Hz, -20dB at 100Hz, -50dB at 20Hz.

Ten years ago a large concert venue near me had massive noise complaint issues, and were on the verge of being shut down because of them. At the heart of the issue was the bass. This, after they paid a consulting firm $25k to do a study, create a community noise standard, and install a computerized system in the FOH that warned when the standard was being exceeded. Despite the fact that the standard was not exceeded the complaints continued.
Then they hired me to fix it. It took me all of 30 seconds to find the problem: the level standard and the FOH measuring system were dBA. The bass wasn't even being measured. The clueless consulting firm they'd hired had pissed away $25k, because they followed OSHA standards for industrial noise.
haha Ooops...

Hope they got some money back off the other guys and gave it to you! lol
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post #18 of 20 Old 06-17-2014, 09:39 AM
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haha Ooops...
Hope they got some money back off the other guys and gave it to you! lol
They didn't get a dime. I created a new noise standard, and identified some necessary venue fixes. I also got a job monitoring levels, so basically I was paid to see 300 odd concerts over the next four years.
At that point things were squared away well enough that I walked. I'd rather spend my nights at home. A year ago they expanded the facility and neglected to involve me in the process. Sure enough, I got a phone call from one of the town officers who said that they were getting noise complaints again. After he described what had been done to the facility I diagnosed the problem and told him how to fix it. Must have worked, I didn't hear anything about it again.

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post #19 of 20 Old 06-17-2014, 10:32 AM
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This is interesting and there are many other charts that are similar

http://www.gcaudio.com/resources/howtos/loudness.html

I'm interested in the apple app. How does the mic connect since we are without USB ports?
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post #20 of 20 Old 06-17-2014, 03:06 PM
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Hearing loss and noise complaints are too different things though; although both correlated to high SPL.

I am guessing here, but I would "think" that bass below 115db probably won't cause hearing damage nearly as quickly as 105dbA of 1-20k.
dbA should be just fine unless we are talking absurd levels of car-like bass (115db+).

Op is trying to determine safe exposure to theaters. Not determine noise complaint thresholds.
For noise complaints then yeah dbC (or in the case of wind turbines, probably even Flat) is more suitable for sure!

If I pull out a meter that is in dbA mode and it reads 100dbA+ then I KNOW the sound is approaching dangerous hearing levels.
Conversely, I could read 110dbC on my meter, but that doesn't tell me if it is a 110db 2khz sinewave or 116db 20hz sinewave; the later won't cause any hearing loss, the 2khz will and that is what dbA will detect.
It's important to not to be accidentally fooled by dbC meters or unweighted mics.
I would not trust some random guy off the street to tell me if a system was "safe" by reading a dbC meter, but give that same noob a dbA meter and his lack of knowledge becomes irrelevant; the dbA does the work for him. But of course having a trained person asses the meter would be even better.
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