bluetooth headphones, how to tell if A2DP is being used

[lazydays]

I found this in the system profiler but it wasn't very enlightening:

DR-BT21G:
Name: DR-BT21G
Address: 00-1d-ba-29-46-7e
Type: Handsfree
Services: Headset, Hands-Free unit
Paired: Yes
Favorite: Yes
Connected: No
Manufacturer: Cambridge Silicon Radio ($3, $d55)