Three sources of sound $S_1, S_2$ and $S_3$ of equal intensity are placed in a straight line with $S_1{S}_2=S_2{S}_3$. At a point $P$, far away from the sources, the wave coming from $S_2$ is $120°$ ahead in phase of that from $S_1$. Also, the wave coming from $S_3$ is $120°$ ahead of that from $S_2$. What would be the resultant intensity of sound at $P$?

Two coherent narrow slits emitting sound of wavelength $\lambda$ in the same phase, are placed parallel to each other at a small separation of $2\lambda$. The sound is detected by moving a detector on the screen $\mathrm{\Sigma }$ at a distance $D (>>\lambda )$ from the slit $S_1$, as shown in the figure. Find the distance $x$ such that the intensity at $P$ is equal to the intensity at $O$.

Figure shows two coherent sources $S_1$ and $S_2$ which emit sound of wavelength $\lambda$ in phase. The separation between the sources is $3\lambda$. A circular wire of large radius is placed in such a way that $S_1{S}_2$ lies in its plane and the middle point of $S_1{S}_2$ is at the centre of the wire. Find the angular positions $\text{θ}$ on the wire for which constructive interference takes place.

Two sources of sound $S_1$ and $S_2$ vibrate at same frequency and are in phase. The intensity of sound detected at a point $P$, as shown in the figure, is $I_0$.

$\left(\mathrm{a}\right)$ If $\text{θ}$ equals $45°$, what will be the intensity of sound detected at this point, if one of the sources is switched off?

$\left(\mathrm{b}\right)$ What will be the answer of the previous part, if $\text{θ}=60°$?