Q: external usb microphone not working with FaceTime and mac mini with os x Yosemite

While I'm glad this worked for you, it has not for myself and others.

It does make me hopeful that there is a way to correct this behavior in software.

Yeah, I"ve got the same problem as well.  Seems to always want to use the built-in microphone instead of my external USB one (even when it is selected as the Microphone to use in FaceTime).

i tried this... "sudo killall coreaudiod" in terminal and my usb webcam microphone then works fine... but only until i reboot. When i reboot the machine i have to copy and paste this again into terminal. This there anyway to make this permanent ??

While I've not tested, perhaps this thread can help:

running shell script at startup (before login)

Basically set up a the command as a shell script to run upon login.

Glad this works for you, perhaps we will see more comments from USB mic users. 

I have the sis, it only works like <once>, then the microphone quits working.  The mic is a Blue Snowball - works great otherwise.  And what's odd is that FaceTime still works - I can make/receive FT calls just fine, I just can't answer my iPhone.  I can pick it up, but the little sound graph display doesn't budge when I'm making noises.  After I disconnect, the mic works fine elsewhere.

Im Just another user with the same issue.

I have a Blue Yeti USB External Mic on a Mac Mini.

Running the command did work for me... but not sure what will happen when I reboot.

Its a bug that will be squashed in future versions I am sure.

Same issue.  I have a logitech webcam.  Microphone does not work when trying to make phone calls via my iPhone 6.  I hope this gets fixed.  Was looking forward to using my mac mini as a speaker phone while on conference calls. 

Some appens to me with my usb headphone.

Mike is not recognized, although it appears in the preferences panel.

Even if I enable USB microphone, the computer takes the the machine default microphone and I cannot use my apps.

Why Apple makes so big errors ??

Have we to pray for 10.10.01 ??

Same problem with Logitech external. Killing coreaudio does nothing.

The terminal command works for me.  I haven't tried rebooting, though.

I am using the mic on a USB webcam and was having trouble getting audio while making calls through iPhone 6. 

Very handy feature. 

Thanks!!!

Was using Microsoft LifeChat LX-6000 USB stereo headset on Mavericks for: audio, Cisco VoIP app (Cisco Jabber) and videconference app (Sandberg Movi, now Cisco Jabber Video).

iMac (27-inch, Late 2012) updated to Yosemite, USB audio no longer works.

This command did not work for me:

     sudo killall coreaudiod

This is my office machine so I need to get this sorted out pretty quickly!

This worked for me! Thanks. Although, in my case, I could not get audio from the built-in mic on my early 2008 MBP.

Now I can.

Thanks again.

UPDATE: And... it stops working after reboot as well ...

The terminal command doesn't work for me. Hope Apple fixes this soon.

Same here on a Mac Pro 09 with Logitech C930e webcam - mic selected in FaceTime but no-one can hear me when calling via iPhone

Me too! Go Mic by Samson on my Mid-2011 Mac Mini. Want to use the Yosemite FaceTime/iPhone feature with audio only. Mic receives signal in Sys Pref, calls come through and ring out ok via my iPhone 5S, but mic isn't recognised by the app.