According to Verizon Wireless the data usage for audio streaming is 60 MB/hr.
Audio Track Download (3 1/2 min at 192 kbps) = 7 MB
1 MB = 1,024 KB
1 GB = 1,024 MB
Verizon Wireless Data Calculator
verizonwireless.com/b2c/splash/dataShareCalculator.jsp