Under what condition, te Doppler will not be observed, if the source of sound moves towards the listener ?

Under what condition, te Doppler will not be observed, if the source o

1.	Under what condition, te Doppler will not be observed, if the source of sound moves towards the listener ?
Answer» Solution :Doppler effect will not be OBSERVED, if the SOURCE of sound moves towards the listener with a velocity GREATER than the velocity of sound. Same is ALSO true if listener moves with velocity greater than the velocity of sound towards the source of sound.