Does an oscillating source always produce sound waves?

$A$ tuning fork of frequency $220 \,Hz$ produces sound waves of wavelength $1.5 \,m$ in air at $N.T.P$. The increase in wavelength when the temperature of air is $27^{\circ} C$ is nearly $\left(\sqrt{\frac{300}{273}}=1.05\right)$ (in $\,m$)

The temperature at which the speed of sound in air becomes double of its value at $27^\circ C$ is ... $^\circ C$

How does the speed of a sound wave depend on the absolute temperature of air?

The velocity of sound in air is doubled when the temperature is raised from $0^{\circ} C$ to $\alpha^{\circ} C$. The value of $\alpha$ is . . . . . . .

Sound velocity is maximum in