They bless those who offer the oblationThe Sraddha ceremony comes under Pitr Yajna. It is the sacred duty of the householder. Every householder should perform the Sraddha ceremony for his ancestors. Pitrs are forefathers who dwell in the Pitrloka.
They possess the power of clairvoyance and clairaudience. When Mantras are recited, they exercise tremendous influence through their vibrations.
The Pitrs (ancestors) hear the sounds through the power of clairaudience and they are pleased. They bless those who offer the oblation.