[ag8908]

Can an expert please confirm if this is a not a terribly error ridden and inappropriate way to measure dbA output of headphones/IEMs?
 
I am trying to measure the dbA of sound going into your ear canal, whether by way of an IEM or headphone. I'm also trying to figure out at what volume level an IEM is equivalent to an over the ear. Same with speakers (I obviously know how to measure that, just put the meter in the air). This is just for fun/curiosity. For example, I seem to need 8-10 bars of volume on my LG G Flex phone to get my Shure SRH940 into the 70 dbA output area (average), but I only need 3 bars of volume on my Shure SE846 IEM to get into that 70 dbA range. Based on this, I put the headphone and IEM on at this purported 70dbA level, to see if my ears could confirm that they had the same volume, but ultimately I could not be sure because they sound so fundamentally different.
 
What do you guys think? Is there some horrible error being introduced by this measurement technique? Or is it good for an approximation?
 
First pic is how I measure dbA output from the IEM, and the second shows how I measure it from the headphone.
 

 

[esldude]

I think there would be plenty of error.  I have a few ideas on what might be better, but none are all that simple.
 
http://www.innerfidelity.com/content/expert-tests-innerfidelitys-headphone-measurement-repeatability-and-reproducibility
 
Here is a good analysis of measured differences where they did multiple measures using a good dummy head.  Just repositioning the phones between measured made some large differences. relatively speaking.  And your method would have far more variance than this.  I realize you aren't trying to do the same detailed measurements.  But I think the error is large enough you need a bit more effort for the comparison to mean much at all. 

 

[ag8908]

Thanks for the link I'll read it when I'm near a big computer screen. Accepting that the headphone measurement is probably off, is it fair to say that the iem measurement should be pretty close? Since that's just going right into you ear canal and it's sealed?

 

[higbvuyb]

Thanks for the link I'll read it when I'm near a big computer screen. Accepting that the headphone measurement is probably off, is it fair to say that the iem measurement should be pretty close? Since that's just going right into you ear canal and it's sealed?

You probably need at least a 2cc coupler for good results with an IEM.
 
From the Master, Don Wilson:
 
http://www.head-fi.org/t/7972/ety-power-handling-and-other-questions/15#post_93448

 

[ag8908]

Thanks. Hopefully this method is within 3 dba or so? I'll have to read the article though.

 

[ag8908]

Oh I see the purpose of the coupler is to measure dba hitting your ear drum; I think that might actually be unhelpful because when people talk about dbA they're thinking of the dbA that would be heard at the opening of you ear canal. So I think a coupler would give you results that wouldn't give apples to Apples numbers comparable to the way others talk about dbA.
 
Thanks again fur the link. Excuse typos on phone

 

[higbvuyb]

You'll get an eardrum SPL measurement, yes. You can convert that to a free field SPL, though (but that won't work with an SPL meter)

 

[ag8908]

I should note that I use the iem tip as essentially a couplerif you look closely. When taking the measurement I maintain a seal between the tip and meter.
 
Link to a place where you can convert eardrum dbA to field free dbA? I'll see if I can Google it.