Apple - MacBook Pro creates soft hissing sound through headphones

Tough to know for certain, but my money is on an impedance mismatch between the output of the Macbook and your new headset. Or, perhaps more accurately stated, excessively sensitive (low impedance) headphones are revealing flaws in the MacBook audio output circuit.

Care to share the model of headphones you're now using? My guess is it's a low-impedance model intended for use with portable audio devices. You can boost the impedance by adding an in-line volume control adaptor like the Shure EA650. You will find other suggestions for solving this problem, including some DIY answers, by searching the forums at Head-Fi.org

For more information/background see: Impedance, and how it affects audio equipment by Rod Elliot and Sound On Sound: Understanding Impedance.

---

Another possible solution: I have M-Audio powered monitors plugged into my MacBook Pro, and plug my Etymotic earplugs into the headphone jack on the monitors for private listening. I haven't noticed any noise problems with this set-up.

I have had the same hissing with my MacBook Pro and a pair of Sennheiser CX300-II in-ear headphones. I solved this by changing the output format of the Built-in Output device from 48kHz/2ch-16bit to 48kHz/2ch-32bit.

This can be done as following:

• Open Audio MIDI Setup. Use Spotlight to find it or find the application in your Utilities folder
• Make sure your headphones are plugged in
• Click on `Built-in Output'
• On the right it will say Source: Headphones and format will be 48000.0 Hz / 2ch-16bit
• Click on 2ch-16bit and choose 2ch-32bit from the drop down menu

I choose 2ch-32bit, but I've noticed that any other value than 2ch-16bit already eliminates the noise.

I am still in the process of figuring out why this works, anyone with more understanding of this issue, please feel free to edit my answer accordingly.

I had the same buzz noise as questioned. Though, it went away when i unplugged my MacBook from the adapter. The buzz appeared every time i used a specific power socket. Changing the power socket made the noise go away.