What is carried by the waves? Mass,velocity,or energy?

The intensity of a sound wave while passing through an elastic medium falls by $10\%$ as it covers $1 \ m$ distance through the medium. If the initial intensity of the sound wave was $100 \ dB$,its value after it has passed through $3 \ m$ thickness of the medium will be .... $dB$.

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

$A$ musical instrument $X$ produces sound waves of frequency $n$ and amplitude $A$. Another musical instrument $Y$ produces sound waves of frequency $\frac{n}{3}$. The waves produced by $X$ and $Y$ have equal energies. The amplitude of waves produced by $Y$ will be (in $A$)

The intensity of sound after passing through a slab decreases by $30\%$. On passing through two such slabs,the intensity will decrease by ..... $\%$

$A$ musical instrument $P$ produces sound waves of frequency $n$ and amplitude $A$. Another musical instrument $Q$ produces sound waves of frequency $n/4$. The waves produced by $P$ and $Q$ have equal energies. The amplitude of waves produced by $Q$ will be