$A$ wave has simple harmonic motion whose period is $4\; s$,while another wave which also possesses simple harmonic motion has its period $3\; s$. If both are combined,then the resultant wave will have the period equal to ....... $s$.

Two waves $Y_1 = 0.25 \sin 316t$ and $Y_2 = 0.25 \sin 310t$ are propagating along the same direction. The number of beats produced per second are

Two wires are in unison. If the tension in one of the wires is increased by $2\%$,$5$ beats are produced per second. The initial frequency of each wire is .... $Hz$.

When two tuning forks are sounded together,$5$ beats per second are heard. One of the forks is in unison with $0.97 \ m$ length of sonometer wire and the other is in unison with $0.96 \ m$ length of the same wire. The frequencies of the two tuning forks are

$A$ tuning fork of frequency $280\, Hz$ produces $10$ beats per second when sounded with a vibrating sonometer string. When the tension in the string increases slightly,it produces $11$ beats per second. The original frequency of the vibrating sonometer string is ... $Hz$.

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