a) If an infant can scream at a sound level of 106-d? measured at a distance 12-cm from their mouth, how far away should a parent stand so that the child can be seen but not heard? (The threshold of hearing is 0-d?, or equivalently I0 = 10-12-Wm-2.) Assume spherical symmetry for the dispersion of the sound wave energy (this is of course a bad assumption)
b)How much power is the child putting in to screaming?