The intensity of a sound appears to an observer to be periodic. Which of the following can be the cause of it?

Two sound waves having wavelengths $5.0 \ m$ and $5.5 \ m$ propagate in a gas with velocity $300 \ m/s$. The number of beats produced per second is

When two tuning forks (fork $1$ and fork $2$) are sounded simultaneously,$4$ beats per second are heard. Now,some tape is attached to the prong of fork $2$. When the tuning forks are sounded again,$6$ beats per second are heard. If the frequency of fork $1$ is $200 \, Hz$,then what was the original frequency of fork $2$ (in $, Hz$)?

What is beat frequency?

The frequencies of two tuning forks $A$ and $B$ are $1.5 \%$ more and $2.5 \%$ less than that of the tuning fork $C$. When $A$ and $B$ are sounded together, $12$ beats are produced in $1$ second. The frequency of tuning fork $C$ is: (in $\text{ Hz}$)

$A$ set of $24$ tuning forks is arranged in a series of increasing frequencies. If each fork gives $4 \, Hz$ beats per second with the preceding one and the frequency of the last tuning fork is two times that of the first fork,find the frequency of the $5^{th}$ tuning fork in $Hz$.