Source starvation means that somehow the input stream starves probably because the throughput obtained from the stream manager is insufficient for some reason (e.g. due to long seek times on DVD etc.)
Voice starvation means that the sound engine was not able to fill the hardware voice fast enough usually due to too much processing to be done (in which case the audio thread CPU is often near 100%) or because the audio rendering thread was not scheduled for a sufficient time slice due to other higher priority threads.
Understanding the difference between the 2 when one of them is flagged in the profiler will give you a better understanding of the situation
