(a) sound heard directly
`f _(1) = f _(0) ((nu)/(nu + nu_(S))) rArr nu_(S) = 10 m//s`
`:. f_(1) = ((330)/(330 +10)) xx1000`
= `970.6 H_(Z)`
(b) The frequency of the reflected sound is given by
`f_(2) = f_(0) ((nu)/(nu - nu_(s)))`
`f_(2) = ((330)/(330 - 10))xx 1000`
=`1031.25 H_(Z)`