|"We observed that the in-ear and earbud-style earphones produced 7 to 9 dB higher output than the over-the-ear earphones at the same volume control setting. Unfortunately, the popular media over-interpreted this observation and earbud-style headphones got a bad rap!"
You are, too, over-interpreted what that one paragraph said. If you read on:
|"I’m glad we got back to this, as this is an important point. In our study, we found that the level of background noise had a direct effect on a user’s chosen listening level. For instance, in a quiet sound booth (background noise level is low, about 28 dBA) about 6% of headphone users chose levels above 85 dBA. (We might consider 85 dBA as a cutoff for “riskier listening behavior.”)
When background noise was raised to 80 dBA of airplane cabin noise (as though subjects were listening to their headphones while flying on an airplane), 80% chose levels above 85 dBA. This was seen irrespective
of whether they used an earbud or an over-the-ear earphone, as long as the
earphone provided no sound isolation.
However, when subjects listened in that airplane noise condition using the ER6i (Etymotic Research, Inc.), an earphone with sound isolation, only 20% listened above 85 dBA. This earphone provided an average of 25 dB of sound isolation according to our measures for each of our 100 subjects."
|"Yes, using a sound-isolating earphone will generally cause a person to moderate their listening levels. This assumes that it isn’t necessary for the person to be able to hear in their surroundings (that is, it’s not necessary for safety or communication reasons to be able to hear well).
Consider it a matter of signal-to-noise ratio. If background noise is masking the sound you want to hear (like music), you’ll turn up that signal. In a noisy background (for example, on a plane), people will typically turn up the music so they can hear it over the noise. For those people who would usually choose a moderate level in quiet, but turn it up in high background noise, using sound-isolating earphones has a direct impact on listening behavior."
What the author means is: if you use an IEM, you are more likely (as 80% of people do) to turn down the volume, thus resulting in less volume and less likely for hearing damage to occur. In fact, many people choose to use IEM because we can turn our volume down yet enjoy great SQ in noisy environment.
Also note that, while an good closed headphone can block out about 80% (or less) of noise, an good IEM can easily block out >90% of noise.