WHO Says What!?

As I opened my news feeds yesterday morning I found a glut of reports about "International Ear Care Day" on March 3rd and recent recommendations from the World Health Organization to bring awareness to hearing health and preservation. The numbers are sobering.

  • 1.1 billion teenagers and young adults are at risk of hearing loss due to the unsafe use of personal audio devices.
  • Among teenagers and young adults aged 12-35 years, nearly 50% are exposed to unsafe levels of sound from the use of personal audio devices and around 40% are exposed to potentially damaging levels of sound at entertainment venues.
  • Between 1994 and 2006, the prevalence of hearing loss among teenagers 12 to 19 years old rose significantly from 3.5% to 5.3%. This rise may be expected to continue as the number of people listening to music through headphones increased by 75% from 1990 to 2005 in the United States.

Recommendations from the WHO are pretty comprehensive and are spelled out in their "Make Listening Safe" brochure, which includes these tips for young folks:

  • Keep the sound from your player below 85dB. Volume control at 60% as a rule of thumb.
  • Where ear plugs in loud environments like clubs and concerts.
  • Use noise canceling headphones so you don't have to raise the volume too high to overcome outside noise.
  • When at a club or concert take short "listening breaks" away from the sound to help reduce exposure duration.
  • Move to quieter locations in the venue (away from the speakers) to enjoy the music at a lower level.
  • Limit use of personal audio devices to less than one hour per day.

That last one is the tough one. I'm not sure I could even pull that one off, much less my teenager. The thing is, it is damned important to get the gist of this message across. It's really largely about the intensity of exposure over time. And worse, this damage can be happening without symptoms like ringing in the ears or any indication of trouble. The damage can lay dormant for long periods of time and then pop up as you age.

But how are you going to convince your teen that this is important? Let me suggest the gift of good hearing with the gift of good headphones and some good attenuator ear plugs. I suggest you, completely out of the blue, buy these items for your youngster and take that moment of surprise to also spend some time talking about hearing safety. Here are some resources for that conversation:

Please help your youngster keep their hearing and the joy of music throughout their entire life.

COMMENTS
tony's picture

Well, lets see:

One bit equals 6db, 85db would be, hmm, 14 Bits.

That kinda says that 16/44.1 is about all our ears can handle.

So why are those folks trying to sell us 24 Bit recordings? , 24 Bits would have 144db. of dynamic range , that's 59db of signal pressure level above what is safe for humans.

OUCH!

Is the World Health Organization giving us music lovers permission to stay with Red Book CD standards?

I read this as another reason to not waste the money on the "more expensive" download versions of music that feature 24/192 type specifications.

I guess this makes me "Old School" now.

Tony in Michigan

ps. thanks for passing this on, Tyll.

Tyll Hertsens's picture
...but I always enjoy your posts, mate.
steaxauce's picture

Tell me if I'm off my rocker, but this is my understanding of it. Take two files of the same recording, one 16 bit, one 24 bit. Make a third file, the subtractive difference between the two. The audio in this third file should be representable by only the 8 least significant bits, giving it at most 48dB dynamic range.

Now, set your volume so that peak loudness is 85dB. The audio in the difference file you created will occupy the space between -59dB and -11dB, where 0dB is the threshold of human hearing. This means the difference between the two files shouldn't be audible, even when isolated from the main signal and played back in absolute silence. It seems odd to think we should be able to hear it when it's added back to the main audio file. That's like hearing a spec of dust land on the carpet when your main speaker rig is playing at a solid level.

Here's a general audio question: Is it ever possible to hear a difference between two audio components/files when the subtractive difference between them, when you isolate it, is below the threshold of human hearing? Seems odd to me.

Rillion's picture

I think steaxauce is on the right track but I am not sure about the details of his argument. I prefer to think of it in concrete terms of voltage levels from a music source. For example, a music source that outputs a range of -1 to +1 volt. One bit is used to represent the sign of the voltage, so a 16 bit number represents 2 to the power of 15, or 32768 voltage levels. Each step is then 1 volt/32768 = 3.05E-05 volts. In other words, the lowest non-zero voltage that can be represented is about 3.05E-05 volts. In terms of dB below the peak that is 20*log10(3.05E-05 volts / 1 volts) = -90 dB below the peak. If the peak should be 85 dB (90 dB in short bursts may occur in some highly dynamic music, but let's stick with 85 dB), that means 16-bits can represent sounds that are 5 dB below the audible threshold (for pure tones -- a caveat that some may criticize), or equivalently, such small sound differences superposed on top of louder sounds which as steaxauce was arguing (if I understand correctly) should not really be audible.

However, if you do some sort of audio processing like applying multiple equalization filters, then one might worry that 16 bits is not enough--I haven't thought this through myself in a convincing way.

Let's repeat the above example using 24-bits: 2^23 = 8388608 levels, so 1.19E-07 volts per step and 20*log10(1.19E-07 volt/ 1 volt) = -138 dB. In other words, -138 dB + 85 dB = -53 dB. 53 dB below audible should be good enough even for pro work with all sorts of gain adjustments, equalization, and mixing.

tony's picture

Dear Tyll,

Yes, it isn't anything as "simple" as dynamic range alone.

Music reproduction "Mysteries" are the reason I'm following along on this site since I saw you and Steve G on one of those panels at RMAF back 4 or 5 years ago, my Local lad Jude was on that panel too ( throwing water on the Thunderpants discussions ).
Back then I felt you to be the Scientist, Steve the credible "reviewer" with Jude being the smiling Salesman of "anything and everything" guy that we manufacturers turn to to keep our numbers up.

I've probably read all you're and Steve's posts since then.

Thank you for all this hard work!

Tony in Michigan

ps. I'm pleased to see you've survived another Winter, I hope this one will be my last in the Freezing North, I'm getting too darn old for all this Ice & Wind-chill although I did complete 6 Teaching Company Courses and collect a couple hundred nice CD musics, three winter months in my Lazyboy has it's benefits!

ps.2 That Joker fella is a god send

zobel's picture
zobel's picture
collateral's picture

One hour does seem short since a lot of albums last that much or even longer, but I don't see how anyone who's past high school age can have the time to listen to music for hours (and I'm talking 3+ hours) on end. Especially if it's consecutively and I do see a lot of people with their headphones glued to their heads everywhere they go. I do think your appreciation for music drastically diminishes when you listen to so much of it all the time. It becomes background noise for you.

I'm also very interested to see how my generation will cope with hearing loss in their twilight years. I think hearing aid companies will see a huge boom in business in the next few decades!

AsSiMiLaTeD's picture

I think the problem a lot of people having is knowing how much is too loud. It would be nice to at least have a baseline reference to start with to give us an idea of what 80db or 90db sounds like.

So for example, if I plug the Apple EarPods into an iPhone 6 using the stock Music app with no EQ applied playing a given reference track at 12 (of the 16 'indicator' bars) that would yield a given db level.

Does something like that already exist???

Gooberslot's picture

Since phones already have a built-in mic how about an app than can calibrate maximum safe listening level by putting the headphone against the mic. I know it wouldn't be 100% accurate but it might work. Of course, I realize this wouldn't work for stand alone mp3 players.

Jamey Warren's picture

While I haven't tested it for accuracy, there is an app called CanOpener (http://canopenerapp.com/) that includes a Dosimeter with SPL meter. The SPL meter works based on your chosen model of headphones. Though not relevant to the discussion, the app has some other nice features too, crossfeed, eq, and headphone optimization.

tony's picture

Dear Tyll,

Stereo Exchange

Dave Wasserman got going strong with headphones a year ago or more. He's pulling in some heavy hitters, as he always seems able to do.

By the way, is that Aurilac Vega "the" DAC now-a-days?, I seem to remember you mentioning it to be your fav.

Too sad, you not able to fly out to NY for this, you're Fan Base would love to see and meet you, you'd be a huge draw for the Show.

Tony in Michigan

ps. Of course NY is filled to brimming with the Lunatic Fringe types but they won't drug you so you'll be safe and in good hands. Stereo Exchange and Dave Wasserman are the top dealers in the Area, maybe the entire East Coast, it's an outfit with integrity. I'll be in Europe, so I can't be there.

Tyll Hertsens's picture
Thanks Tony, but I think you posted in the wrong thread.
GNagus's picture

I can't follow these guidelines. They will disrupt self-help seminars and Genesis "Calling All Stations".

tony's picture

I know but this is the thread where all the action is.

She & Him just arrived today, it's not-so good music very well recorded so I love it. Funny how recording quality of 5 Stars makes a so-so music a keeper.
In fact I just got about 10 CDs from the PILZ people in West Germany who are distributing superb quality re-issues of 1960s Jukebox Rock songs ( the kind of music you'd hear at any local Hot Rod Car show ).
Quality is darn good for music we only heard thru crappy radio or 45s back in the day.

Recording Quality carries the day here, even if the music would be otherwise horrible or forgettable.

Tony in Michigan

ps. Are you preparing to do a Wall of Fame "re-fresh" for DACs?, the $2,000 price point is about to see something from Antelope and even Schiit. Everyday headphone people are moving up the price escalator now, we'll be seeing plenty of $2,000 to $5,000 product going begging for proper evaluations.

Gandasaputra's picture

WHO needs to put how loud is the loudness of each mp3 players/DAPs. Like in my Sansa Clip zip, I always play my songs at 2/8 bar at "normal volume" setting so how much DB is that? I listen songs at comfort level that I can go on for 3-4 hours without getting fatigues, unless if my ears needed some fresh air.

zobel's picture

Pretty good info here covering this topic, except they didn't cover circumaural cans;

http://www.generationdeaf.com/headphonehazards.html

ina's picture

I'm very glad the WHO has said this, and I hope manufacturers limit the maximum volume of their headphones and players to around 100 db, and include this advice with all their leaflets and manuals.

But why say volume control at 60%? You don't know what the maximum volume is set at. 100% could be anything from 80 to 200 db

bluecap's picture

Good headphones can cause hearing loss just as easily as bad ones. The problem is the concept of "headroom" or that feeling you get when the volume is loud enough that the music is overwhelming your senses and floating around all over your head. That's what headphone listeners go for, and it's the level of sound that results in hearing loss.

Stefraki's picture

If headphones have good isolation, then people will generally listen to them at a safe volume. It's because the majority of people use free earbuds in public, which do a horrible job of isolating any outside sound, that people crank them up and damage themselves.

Really they should be banned in public for everyone's good. Irritating to people not wearing them to hear their constant tinny leakage, really bad for the hearing of the kid wearing them.

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