I have a similar problem to you. Have completed and compiled the Pickers app and everything works well on the simulator with the exception of sound. No errors or crashes so this is a truly silent fail.
I've played with various settings for the MAC sound card, accompanied by numerous reboots to no avail. The sounds do work when I install the app on an iPad so whatever is wrong appears to relate specifically to the Simulator.
Did you manage to solve your issue?
I'm using the following:
Model Name: MacBook Pro
Model Identifier: MacBookPro11,2
Processor Name: Intel Core i7
Processor Speed: 2 GHz
Number of Processors: 1
Total Number of Cores: 4
L2 Cache (per Core): 256 KB
L3 Cache: 6 MB
Memory: 8 GB
Using Xcode 6.1.1
January 2015