$y =-0.21 \sin ( x +30 t )$
$(x$ in meter $\&$ $t$ in sec)
$v =\frac{\omega}{ k }=\frac{30}{1}=30 m / s$
$v =\sqrt{\frac{ T }{\mu}} \Rightarrow T = v ^{2} \mu=(30)^{2}(0.0135)$
$=12.15$
$= x \times 10^{-2} N$
$\Rightarrow x =1215$
(Take speed of sound in air as $340\, {ms}^{-1}$ )
