The intensity level at a distance of $200 \ cm$ from a sound source is $80 \ dB$. If there is no loss of acoustic power in the air and the threshold intensity of hearing is $10^{-12} \ W/m^2$,what is the intensity level at a distance of $400 \ cm$ from the source (in $dB$)?

Two waves are represented by
$y_1 = 5 \sin 2 \pi(75 t - 0.25 x)$
$y_2 = 10 \sin 2 \pi(150 t - 0.50 x)$
The intensity ratio $\frac{I_1}{I_2}$ of the two waves is

The clocktower ("ghantaghar") of Dehradun is famous for the sound of its bell, which can be heard, albeit faintly, up to the outskirts of the city $8 \,km$ away. Let the intensity of this faint sound be $30 \,dB$. The clock is situated $80 \,m$ high. The intensity at the base of the tower is ............. $\,dB$.

The ratio of intensities of two waves is given by $4:1$. The ratio of the amplitudes of the two waves is

The amplitudes of two waves are in the ratio $5 : 2$. If all other conditions for the two waves are the same,what is the ratio of their energy densities?

$A$ stationary point source of sound emits sound uniformly in all directions in a non-absorbing medium. Two points $P$ and $Q$ are at a distance of $4 \ m$ and $9 \ m$ respectively from the source. The ratio of amplitudes of the waves at $P$ and $Q$ is