Q.State the general Doppler-effect formula for the frequency heard by an observer when both the source and the observer are in motion, defining every symbol and the sign convention used for the source's and the observer's velocities.

The Doppler effect is the shift in a sound's apparent frequency due to relative motion between source and observer: $f'=f_0(v+v_o)/(v-v_s)$, with $v_s$ positive when the source moves toward the observer and $v_o$ positive when the observer moves toward …