$A$ tuning fork of frequency $n$ produces $x$ beats per second when sounded with a vibrating sonometer string. What must have been the frequency of the string, when a slight increase in tension produces lesser beats per second than before?

Two sound waves of wavelengths $\lambda_1$ and $\lambda_2$ $(\lambda_2 > \lambda_1)$ produce $n$ beats per second. The speed of sound is:

Two tuning forks $A$ and $B$ produce $4$ beats per second. The frequency of $A$ is $256 \ Hz$. On loading $B$ slightly,the beat frequency becomes $5$ beats in $2$ seconds. The frequency of $B$ after loading is .... $Hz$

When two tuning forks (fork $1$ and fork $2$) are sounded together,$4$ 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 the original frequency of fork $2$ is ........... $Hz$.

Two sitar strings,$A$ and $B$,playing the note $'Dha'$ are slightly out of tune and produce beats at a frequency of $5 \, Hz$. The tension of string $B$ is slightly increased and the beat frequency is found to decrease to $3 \, Hz$. If the frequency of $A$ is $425 \, Hz$,the original frequency of $B$ is ... $Hz$.

When a vibrating tuning fork moves towards a wall,why do we hear sound beats?