Popping and sibilance:
Popping occurs when words containing Ps & Bs (like popping and barbecue) are sung or spoken Try saying popping or barbecue with your hand directly in front of your mouth. You will feel the extra burst of air when saying these words compared to words without Ps or Bs. When using a microphone to capture vocals the burst of air will head straight for the unprotected microphone and can cause overload distortions in the mic and associated electronics.
Sibilance is the excessive hissing when pronouncing Ss and Zs. Sally sells seashells by the seashore is a phrase that would emphasize sibilance. Sibilance can also overload an unprotected microphone and associated electronics.