Peak @ 7Khz is due to 21/32 (.656") length of the plastic ear canal , + .3" offset by larger tip which set the driver at about .957" from mic element. This is a half wave length of 7khz. the reflection constructively interferes. (C≈13500 in/sec @ 20 degC. ƒ=C/λ)
Peak @ 8.9Khz is due to 21/32 (.656") length of the plastic ear canal , + .1" offset by tip which set the driver at about .756" from mic element. This is a half wave length of 8.9khz. the reflection constructively interferes.
Here we have better low frequency response, probably due to a better seal. (wish I could get this good a seal in my ears)
The bump @ 2.7khz appears to be the same for both. Is it not related to canal length?
Same as above, but with plastic ear canal filled with open cell foam. Note some flattening of the response without significant overall attenuation. I suspect that this is due to attenuation of standing waves, which is why I put it in there.
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