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The magic 85db number

post #1 of 23
Thread Starter 
Ok I have a question for you and i hope this is the right forum section for it.

Is it possible to have 2 different headphones, both matched to 85db on an spl meter yet one appear louder than the other???

Confused? Me too lol (if your not then your the person I'm looking for lol)

I'll explain. I have a pair of sen HD555 and the new Bose AE2. I have been researching hearing loss and headphones and have found the magic 85db limit. So I got an spl meter for iPhone app to test them.

So I shoved my iPhone mic into the HD555 and formed a seal with my hand and turned up volume on iPod until the avg db reading was 85db, then I did the same with the AE2.

Now the HD555 sound louder at 85db than the AE2 do! Is that even possible? Have I measured wrong?

Also it has to be said, 85db is much louder than I thought it would be, and my typical listening volume ( assuming i have done it right) is 70-75db. Do you guys and gals find 85db quite loud too?

So that's a few questions,


Thanks

Troykm
post #2 of 23

Maybe it's all about presentation. Like some cans are forward and some are laid back, no matter the volume. Psychoacoustics is tricky like that.

post #3 of 23

Decibels are weighed across frequencies.  It might be the case that you are less able to hear high frequencies, and the HD555 (which are not particularly bright phones) seem to get most of their average sound energy from frequencies below 10k Hz, which might be what you hear best.

post #4 of 23
Thread Starter 

both good answers. 85db seems really loud, its it really a safe level?

post #5 of 23
Quote:
Originally Posted by troykm View Post

both good answers. 85db seems really loud, its it really a safe level?


 

no. its the level of loudness that permanent hearing loss begins. heres a pretty informative chart-

 

 
Sound Noise Level (dB) Effect
Whisper 30 Very quiet
Quiet Office 50-60 Comfortable hearing levels are under 60 dB
Vacuum Cleaner, Hair Dryer 70 Intrusive; interferes with telephone conversations
Food Blender 85-90 85 dB is the level at which hearing damage (8 hrs.) begins
Garbage Truck, Cement Mixer 100 No more than 15 minutes of unprotected exposure recommended for sounds between 90-100 dB
Power Saw, Drill/Jackhammer 110 Regular exposure to sound over 100 dB of more than 1 minute risks permanent hearing loss
Rock Concerts (varies) 110-140 Threshold of pain begins around 125dB

Edited by Thecoolguy - 12/15/10 at 5:02pm
post #6 of 23

As eucariote said, the human ear perceives different frequencies differently (due to lots of stuff, for example resonance in the ear canal due to different wavelengths, etc.). To work around this, there are weighted response curves (dBA, dBB, dBC,etc.) trying to give a good approximation of perceived loudness for most people. Maybe your iPhone app can measure in dBA? By the way, the iPhone meters are not particularly accurate. I have compared the "SPL Meter" app with a pretty expensive B&K SPL meter, in a quiet studio, and the difference between the two were 20-40 dB (the iPhone fluctuating a lot, B&K stable).

post #7 of 23
Quote:
Originally Posted by Thecoolguy View Post



Quote:
Originally Posted by troykm View Post

both good answers. 85db seems really loud, its it really a safe level?


 

no. its the level of loudness that permanent hearing loss begins. heres a pretty informative chart-

 


In addition an increase in 3dB halves safe exposure time, so at 85dB you might be at risk after a few hours. For interests sake, here's the guidelines for workplaces in the UK: if the levels are "80 dBA Leq over 8h (or 135dBC instantaneous)", then "ear protection must be available on request". 

post #8 of 23
Thread Starter 

so how do you guys manage your sound levels or do you just go full on and not worry so much

post #9 of 23

I listen at what I feel is comfortable level, which I know most of my friends think is too low, so I feel safe:P (I've been anal about not damaging my ears for years.. apparently paid off, as a test I recently took at an audiologist came out with above average results).. 

 

Just keep in mind that the ear gets tired, and what might have started out sounding loud, may not be sounding as loud 30 minutes later. So people tend to increase the volume a little again and again. Taking a few short breaks now and then will let the ears recover and you won't need to crank it up to get the same perception of loudness.

 

Edit: And you can go pretty high without damaging your ears, just keep in mind that how long you are exposed to a certain level is crucial (about 8h safe for 80dB, up to instant damage at 130dB).


Edited by Jodles - 12/15/10 at 5:41pm
post #10 of 23
Quote:
Originally Posted by troykm View Post

so how do you guys manage your sound levels or do you just go full on and not worry so much



I set my levels to a comfortable level and then turn it back a few and listen at that level being careful to not turn up by more than half of the initial reduction. So far, my hearing is fully intact and safe. I would argue that it's even improved over time.

post #11 of 23
Thread Starter 

thanks guys, it all helps. i love music and would rather loose my sight over my hearing smily_headphones1.gif

post #12 of 23
Quote:
Originally Posted by troykm View Post

Ok I have a question for you and i hope this is the right forum section for it.

Is it possible to have 2 different headphones, both matched to 85db on an spl meter yet one appear louder than the other???
 


IME, yes.  I used my SPL meter to test out the Ultrasone S-Logic and to my readings when matched the Ultrasone was louder than my other sets.  Also my experience w/ IEMs versus headphones suggest SPL is not merely a function of loudness.  I actually once asked an Ety engineer if IEMs posed more of a risk due to their direct and sealed nature and he said a dB is a dB.  Well, I'm not so sure that design can't reduce SPL levels and match gains.  Just my experience.  I was quite reluctant to give up my HFI580s due to this and the Mu shielding.  

post #13 of 23

troykm, what test tone does this app produce? A pure 1 kHz sine tone or pink noise?

 

 

Usually, I also listen at levels below half (-10 dB) of that.


Edited by xnor - 12/16/10 at 5:28am
post #14 of 23

A fun fact is that audio equipment of good quality with a good bass response more easily activates the acoustic reflex in your ear, which effectively raises the threshold needed to permanently damage your ear. So better audio equipment crudely means less damage at same listening levels. And being on head-fi, I have a feeling good audio equipment applies to all of you;-)

post #15 of 23

On the other hand, distortion usually goes up with volume increase, and high levels of distortion usually force you to bring the volume down but good audio equipment have low distortion at high volume,encouraging you to listen louder.

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