Headphones

Started by Bonehelm, June 10, 2007, 02:50:21 PM

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DavidRoss

"Maybe the problem most of you have ... is that you're not listening to Barbirolli." ~Sarge

"The problem with socialism is that sooner or later you run out of other people's money." ~Margaret Thatcher

mc ukrneal

Quote from: DavidRoss on April 22, 2013, 04:38:53 PM
So the answer is "no"?
I was not in on this discussion, but it is a topic of interest for me. I found one link to research that does seem to indicate some preference for over the ear headphones to earbuds, but it does seem that volume is a far more important factor (regardless of type).
Link: http://www.cbsnews.com/2100-500368_162-2109712.html

Here's one that says it has almost nothing to do with it: http://www.time.com/time/health/article/0,8599,1827159,00.html

One more: http://archive.techtree.com/techtree/jsp/article.jsp?article_id=69832
Be kind to your fellow posters!!

DavidRoss

Quote from: mc ukrneal on April 23, 2013, 10:43:30 AM
I was not in on this discussion, but it is a topic of interest for me. I found one link to research that does seem to indicate some preference for over the ear headphones to earbuds, but it does seem that volume is a far more important factor (regardless of type).
Link: http://www.cbsnews.com/2100-500368_162-2109712.html

Here's one that says it has almost nothing to do with it: http://www.time.com/time/health/article/0,8599,1827159,00.html

One more: http://archive.techtree.com/techtree/jsp/article.jsp?article_id=69832

Yep, there's a well-established correlation between exposure to high spls and hearing loss, but if anything that should suggest well-designed earbuds that seal out extraneous sound and thus permit hearing adequately at lower volume might even be a wiser choice than buds or cans that don't.  As Maria Muldaur famously said, "It ain't the meat, it's the motion." ;)
"Maybe the problem most of you have ... is that you're not listening to Barbirolli." ~Sarge

"The problem with socialism is that sooner or later you run out of other people's money." ~Margaret Thatcher

Parsifal

I find it plausible that earbuds are worse than over-ear are worse than speakers.  It has to do with transients.

Consider a sharp transient like a stroke on a drum.  Listening to speakers, your ears receive the primary impulse via direct propagation, and some time later multiple secondary impulses via reflection from walls, ceiling, floor, etc.  For a perceived volume level, there is less power in the transient.  With earbuds, there are no reflections, the transient is received raw.  For over-ear, there at least might be some softening of the transient as the sound bounces around your outer ear.

Todd

#624
Quote from: mc ukrneal on April 23, 2013, 10:43:30 AMbut it does seem that volume is a far more important factor (regardless of type).



It seems to me that volume is the only parameter that matters when it comes to headphone-related hearing loss.  The recommendations as to "percent of the maximum" seem misleading or pointless.  If 70% of max on one device delivers 90 dB average volume and 90% of max on another device delivers 80 dB average volume, the former will cause hearing loss and the latter will not.  (Here's a handy guide for safe volume limits and exposure periods.
The universe is change; life is opinion. - Marcus Aurelius, Meditations

People would rather believe than know - E.O. Wilson

Propaganda death ensemble - Tom Araya

DavidRoss

Your url got dropped, Todd. I presume it referred to a chart like this one from the CDC: http://www.cdc.gov/healthyyouth/noise/signs.htm
"Maybe the problem most of you have ... is that you're not listening to Barbirolli." ~Sarge

"The problem with socialism is that sooner or later you run out of other people's money." ~Margaret Thatcher

Todd

Quote from: DavidRoss on April 23, 2013, 01:36:56 PMYour url got dropped, Todd. I presume it referred to a chart like this one from the CDC: http://www.cdc.gov/healthyyouth/noise/signs.htm



It's similar, and I updated the post.  The url is http://www.lowertheboom.org/trice/safedblevels.htm.  It includes OSHA proposed time limits at various SPLs.  One of the prior article links claims that young people will listen at 110+ dB.  Anyone dumb enough to do that will lose hearing quickly, irrespective of what type of headphones or speakers are used.  (And I do believe these types of concerns are what prompted the local orchestra to put angled plexiglass reflectors in front of the horn section.)


85 dB and higher - prolonged exposure will result in hearing loss
90 dBA - no more than 8 hours per day (examples - lawn mower, truck traffic, hair dryer)
95 dBA - no more than 4 hours per day
100 dBA - no more than 2 hours per day (example - chain saw)
105 dBA - no more than 1 hour per day
110 dBA - no more than ½ hour per day
115 dBA - no more than ¼ hour per day (preferably less)
140 dBA - NO EXPOSURE TO IMPACT OR IMPULSE NOISE ABOVE THIS LEVEL (examples - gunshot blast, jet plane at takeoff)
The universe is change; life is opinion. - Marcus Aurelius, Meditations

People would rather believe than know - E.O. Wilson

Propaganda death ensemble - Tom Araya

71 dB

Quote from: Todd on April 23, 2013, 01:54:41 PM


It's similar, and I updated the post.  The url is http://www.lowertheboom.org/trice/safedblevels.htm.  It includes OSHA proposed time limits at various SPLs.  One of the prior article links claims that young people will listen at 110+ dB.  Anyone dumb enough to do that will lose hearing quickly, irrespective of what type of headphones or speakers are used.  (And I do believe these types of concerns are what prompted the local orchestra to put angled plexiglass reflectors in front of the horn section.)


85 dB and higher - prolonged exposure will result in hearing loss
90 dBA - no more than 8 hours per day (examples - lawn mower, truck traffic, hair dryer)
95 dBA - no more than 4 hours per day
100 dBA - no more than 2 hours per day (example - chain saw)
105 dBA - no more than 1 hour per day
110 dBA - no more than ½ hour per day
115 dBA - no more than ¼ hour per day (preferably less)
140 dBA - NO EXPOSURE TO IMPACT OR IMPULSE NOISE ABOVE THIS LEVEL (examples - gunshot blast, jet plane at takeoff)

Since the noise exposure doubles for every 3 dB increase in sound pressure level, this listing isn't reliable in my opinion. For example, 115 dB A-weighted noise for 15 minutes per day is really BRUTAL for ears! For A-weighted equivalent noise levels LAeq the limits for workers are like this:

85 dB - 8 hours
88 dB - 4 hours
91 dB - 2 hours
94 dB - 1 hour
97 dB - 30 minutes
100 dB - 15 minutes
Spatial distortion is a serious problem deteriorating headphone listening.
Crossfeeders reduce spatial distortion and make the sound more natural
and less tiresome in headphone listening.

My Sound Cloud page <-- NEW Jan. 2024 "Harpeggiator"

Todd

#628
Quote from: 71 dB on April 24, 2013, 03:47:14 AMSince the noise exposure doubles for every 3 dB increase in sound pressure level, this listing isn't reliable in my opinion.



I dare say the folks at OSHA knew all this when compiling the list.  I am thus forced to decide whether to believe OSHA or you.  I'll go with OSHA on this, unless you can point to your special credentials in this field, or the work of some other government agency (Finnish? EU?) that has different standards. 
The universe is change; life is opinion. - Marcus Aurelius, Meditations

People would rather believe than know - E.O. Wilson

Propaganda death ensemble - Tom Araya

Todd

Quote from: jlaurson on April 24, 2013, 06:19:54 AMBut googling OSHA and "absurd" is great fun and an entertaining lesson in the fallibility of any organization that doesn't have to justify its existence or its conduct on a regular, rigorous basis.



OSHA certainly has its shortcomings, but when faced with a choice between the recommendations of an agency that has experts at its disposal and a random poster on an internet forum, I must say that OSHA is probably the better bet.  Now, if there are any audiologists on the board who can cover safe SPL levels, that would be most interesting and informative. 
The universe is change; life is opinion. - Marcus Aurelius, Meditations

People would rather believe than know - E.O. Wilson

Propaganda death ensemble - Tom Araya

DavidRoss

Loudspeakers, earbuds, or cans: the question is which best represents Elgar's complex vibrational fields at SPLs adequate for self-induced prefrontal lobotomy?
"Maybe the problem most of you have ... is that you're not listening to Barbirolli." ~Sarge

"The problem with socialism is that sooner or later you run out of other people's money." ~Margaret Thatcher

71 dB

Quote from: Todd on April 24, 2013, 05:39:55 AM
I dare say the folks at OSHA knew all this when compiling the list.  I am thus forced to decide whether to believe OSHA or you.  I'll go with OSHA on this, unless you can point to your special credentials in this field, or the work of some other government agency (Finnish? EU?) that has different standards.

By all means believe who you want. As an acoustics engineer with an university degree I don't "need" to make you believe what I say. Just don't say I didn't warn you if 15 minutes of A-weighted 115 dB per day makes you deaf.  ???

http://www.osha.gov/SLTC/noisehearingconservation/index.html
OSHA uses 5 dB exchange rate*. The page mentions that NIOSH uses the same rules and limits I mentioned here. In Finland, the 3 dB exchange rate is the only one as far as I know.

* Exchange rate: The relationship between intensity and dose. OSHA uses a 5-dB exchange rate. Thus, if the intensity of an exposure increases by 5 dB, the dose doubles. Sometimes, this is also referred to as the doubling rate. The U.S. Navy uses a 4-dB exchange rate; the U.S. Army and Air Force use a 3-dB exchange rate. NIOSH recommends a 3-dB exchange rate. Note that the equal-energy rule is based on a 3 dB exchange rate.

Source: PREVENTING OCCUPATIONAL HEARING LOSS — A PRACTICAL GUIDE — U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES, 1996.


Spatial distortion is a serious problem deteriorating headphone listening.
Crossfeeders reduce spatial distortion and make the sound more natural
and less tiresome in headphone listening.

My Sound Cloud page <-- NEW Jan. 2024 "Harpeggiator"

Todd

Quote from: 71 dB on April 24, 2013, 11:06:59 AMJust don't say I didn't warn you if 15 minutes of A-weighted 115 dB per day makes you deaf.



Why would I need a warning from you regarding exposing myself to 115 dB sounds?  What a strange reply.
The universe is change; life is opinion. - Marcus Aurelius, Meditations

People would rather believe than know - E.O. Wilson

Propaganda death ensemble - Tom Araya

71 dB

Quote from: Todd on April 24, 2013, 11:57:16 AM
Why would I need a warning from you regarding exposing myself to 115 dB sounds?  What a strange reply.

Following OSHA limits means significantly higher "allowed" noise exposure.
Spatial distortion is a serious problem deteriorating headphone listening.
Crossfeeders reduce spatial distortion and make the sound more natural
and less tiresome in headphone listening.

My Sound Cloud page <-- NEW Jan. 2024 "Harpeggiator"

Parsifal

Quote from: Todd on April 24, 2013, 06:39:32 AM
OSHA certainly has its shortcomings, but when faced with a choice between the recommendations of an agency that has experts at its disposal and a random poster on an internet forum, I must say that OSHA is probably the better bet.  Now, if there are any audiologists on the board who can cover safe SPL levels, that would be most interesting and informative.

Perhaps you should consider the fact that 71dB has formal education in the scientific discipline of acoustics and is more qualified to interpret the OSHA rules, since he has a detailed understanding of the concepts involved.  Of course, this would violate your life philosophy, which holds that anyone who disagrees with you obviously doesn't know anything.   ::)

Todd

#635
Quote from: 71 dB on April 24, 2013, 01:00:14 PMFollowing OSHA limits means significantly higher "allowed" noise exposure.


Hmm, "allowed" is an interesting word choice.  To be honest, I still place far more faith in the estimates of OSHA than in your opinion, but irrespective of whether one follows professional guidelines or amateur guidelines, listening to music at 115 dB (or 110, or 100 for that matter) is something only dunderheads do.



Quote from: jlaurson on April 24, 2013, 12:50:46 PMDBAD!


I had to look this particular abbreviation up.  It is very clever. 



Quote from: Parsifal on April 24, 2013, 01:19:49 PMOf course, this would violate your life philosophy, which holds that anyone who disagrees with you obviously doesn't know anything.


This from the person who writes about "raw" transients.  What are those, exactly?
The universe is change; life is opinion. - Marcus Aurelius, Meditations

People would rather believe than know - E.O. Wilson

Propaganda death ensemble - Tom Araya

Parsifal

The energy transfer in a complex signal is not uniform.   It varies with time. 

For instance, if someone presses a key on an organ the pipe starts oscillating and there is a steady transfer of energy until the key is released.  If someone hits a key on a piano there is a very intense burst of energy as the hammer hits the string, then the tone trails off.  You could characterize both by the average energy transfer rate, but the piano note has a higher peak energy.  It is not clear whether the peak energy or the average energy is more significant in determining ear damage.

Another factor is that stapedius muscle, which acts as a volume control in the ear, can protect your inner ear from very loud sounds.  However, a very brief pulse of sound could damage your ear before the spapedius muscle has time to react.  That is why explosions can be especially dangerous to hearing.  The "white noise" machines that people sometimes use to mask sound work by keeping your stapedius muscle engaged, making your ears less sensitive to ambient noise.

As a result, I think that a criteria that says that so many decibels is dangerous is approximate at best, because a given level of noise might be more or less dangerous depending on whether it is continuous or contains strong impulses.

Todd

Quote from: Parsifal on April 24, 2013, 03:12:48 PMAs a result, I think that a criteria that says that so many decibels is dangerous is approximate at best, because a given level of noise might be more or less dangerous depending on whether it is continuous or contains strong impulses.



Do you have any measurements to support your hypothesis, particularly regarding earbuds?
The universe is change; life is opinion. - Marcus Aurelius, Meditations

People would rather believe than know - E.O. Wilson

Propaganda death ensemble - Tom Araya

Parsifal

#638
Quote from: Todd on April 24, 2013, 03:21:39 PM
Do you have any measurements to support your hypothesis, particularly regarding earbuds?

The hypothesis is easy to verify using widely accepted mathematical tools.  The impulse response function can be constructed by tabulating all of the possible paths that sound can propagate from a source to your ear.  After a minute or two of googling I found a page by someone who measured the impulse response function for their living room.

http://pcfarina.eng.unipr.it/Aurora/SAW/RoomSim.html

See Figure 3.  It shows how a sharp impulse gets smeared out by reflections.  Once you know the impulse response function, the effect on a waveform can be found using convolution.  This is how audio processors that simulate the acoustic of a concert hall work.  Based on the graph in the link above, there is no doubt that a room would smear out transient impulses compared with headphones.  Now, since an over-ear headphone is just a little "room" that you put over your ear, the same effect would apply, in principal.  The question is the degree.  Whether the smearing of over-ear headphones compared with earbuds would be significant is not obvious and would require measurement, which I obviously have not done.    However, smearing of transients would only occur for wavelengths which are smaller than the room size, and this means that only relatively high frequency sounds might have their impulses smeared out by over-ear headphones.  So I suspect the difference between over-ear headphones and earbuds would not be large.

The biggest unknown is not the acoustics, which are very straightforward.   The main question is the physiology of the ear, since the NIH not going to allow researchers to experimentally determine how much sound makes people deaf.  All they can do is ask deaf people how much noise they listened to and for how long.

Todd

Quote from: Parsifal on April 24, 2013, 03:50:33 PMThe hypothesis is easy to verify using widely accepted mathematical tools.



So the answer is no, you do not have any measurements to support your hypothesis, particularly as they pertain to "raw" transients, earbuds, and the impact on hearing.  You can suspect all sorts of things; you can prove nothing.
The universe is change; life is opinion. - Marcus Aurelius, Meditations

People would rather believe than know - E.O. Wilson

Propaganda death ensemble - Tom Araya