Products > Test Equipment
Measuring distorting Etymotic earphones with an osciloscope
RBBVNL9:
--- Quote ---I am not sure that you should draw any quantitative conclusions from this setup. The drivers are tiny and are meant to go into a sealed ear canal. I believe that if you place them in free space, radiation efficiency increases with frequency (something like 6 dB/octave, even though the proximity effect of the cardioid mics may offset this to some degree), so there will be a large emphasis on the harmonics.
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Thanks for the reply! Yes, that certainly makes sense. Just in the open air, they are not acoustically loaded as they are designed for and might behave in unintended ways. Unfortunately, I do not have this 'fake head' or whatever they are called for proper tests of in-ear devices.
Still, I find the relative differences interesting: the two earpieces/drivers behave differently, even if tested in free space.
RBBVNL9:
--- Code: ---Mode retail??
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Oops, it should be 'more detail'. Sorry for the typo...
--- Quote ---Anyway, do you not see the earwax filter sticking out of the lower one? I’d start there…
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Yes, I now see in the picture one of them has the filter in there; the other not. The one with the filter is the 'good' one; I remember taking it out of the 'bad' one. Still, for a 1:1 comparison, I should have taken them both out. You learn every day and never can be careful enough when experimenting ;-)
tooki:
--- Quote from: RBBVNL9 on February 20, 2023, 10:15:52 am ---
--- Code: ---Mode retail??
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Oops, it should be 'more detail'. Sorry for the typo...
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Heheh. FYI, that specific type of transposition has a special name, a Spoonerism (after a Mr. Spooner who famously made lots of them, like “well-oiled bicycle” -> “well-boiled icicle”! :D )
As for characterizing your Ety’s, with these tiny acoustic systems, even the tiniest differences in shape, etc. have significant effects on the frequency response, etc. I don’t think any simple setup is capable of providing any meaningful results.
bicycleguy:
Not sure about your instruments but with mine the fft's work a lot better if the signal of interest is full screen but not clipping. Full resolution requires full amplitude.
RBBVNL9:
--- Quote ---Heheh. FYI, that specific type of transposition has a special name, a Spoonerism (after a Mr. Spooner who famously made lots of them, like “well-oiled bicycle” -> “well-boiled icicle”! :D )
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Today I received a new set of Etymotic ER4XR earphones I ordered, and, as always, they include an individual measurement sheet with them. Nice! Interestingly, this sheet also reveals how the manufacturer measures themselves: they use a G.R.A.S. RA0045 Ear Simulator. It's based on the IEC 60318-4 standard.
The manual (page 5) explains that "The acoustic input impedance [...] closely resembles that of the human ear up to 10 kHz and, as a result, loads a sound source in very much the same way.", and also provides the electrical equivalent diagram.
--- Quote ---Not sure about your instruments but with mine the fft's work a lot better if the signal of interest is full screen but not clipping. Full resolution requires full amplitude.
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Good point. I was in an environment where the mics also picked up my voice (when I was making the video ;-). For more serious testing, I'd need both a proper acoustic load, as well as proper full range settings!
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