When I plug my IE80 into my Macbook Air and play any audio, it has a hissing noise in the background. I tried the solution in How can I make my Macbook Pro's headphone jack stop "humming"? by changing audio MIDI setup and it did not work. So I am wondering whether there is some other ways to solve i
I glean from the official specs:
sound pressure level: 125dB
This can mean just about anything, but if my hunch is right in that what they are trying to say is that their sensitivity is 125dB/mW, then this is indeed a highly sensitive set of IEMs, and I'm in no way surprised that they hiss to some extent when plugged into your MacBook Air. While the MBA has pretty low noise levels as far as laptops go, it should still be more than high enough for the IE80s to pick up.
Just to be certain of course: See if the noise changes considerably by plugging and un-plugging the power supply. Also check how much noise you can hear through a more normal set of headphones (iBuds, PortaPros, something like that).
If the noise level is objectionably high only through the IE80s, even when running the Mac on battery power, your choices are essentially to either live with it, use other headphones, or buy a usb DAC/amplifier with a sufficiently low noise level. Something like those from Leckerton or JDS Labs, for example.
I had this same problem with both headphones and my external speakers (both Bose). I had more than just buzzing, I had noticeable pops when I just touched my headphone jack or audio cable.
After struggling with MIDI and sound tweaks forever, what solved my issue permanently was that I got an external (USB) DAC interface.
My first device was the Behringer UCA202 Audio Interface which I connected directly to a Bose Wave radio.
It had the convenience of providing both a optical and analog out as well as another analog input as well as a headphone monitor port. One of the features of a product like this is that it shows up as an additional audio device in System Preferences > Sound. This allows me to pipe music to my Bose while system sounds came out of the system speaker.
What was even nicer about the product was the price; less than $30 when I bought it.
I have since upgraded to the Marantz Hi-Res Audio DAC since I got into Hi-Res Audio. This DAC is obviously overkill if you want to remove hum or the noticeable buzz; it's just absolutely phenomenal in terms of sound quality.
Since going with an external DAC, I don't think I will ever go back to "futzing" around with sound settings trying to perfect it - it's just not worth the time.