A sound absorber attenuates the sound level by $20\,\, dB$. The intensity decrease by a factor of

Two tuning forks $A$ and $B$ produce $8\, beats/s$ when sounded together. $A$ gas column $37.5\, cm$ long in a pipe closed at one end resonate to its fundamental mode  with fork $A$ whereas a column of length $38.5 \, cm$ of the same gas in a similar pipe  is required for resonance with fork $B$. The frequencies of these two tuning forks, are

Dependence of disturbances due to two waves on time is shown in the figure. The ratio of their intensities $I_1 / I_2$ will be

A railway engine whistling at a constant frequency moves with a constant speed. It goes past a stationary observer standing beside the  railway track. The frequency $(n)$ of the sound heard by the observer is plotted against time $(t).$ Which of the following best represents the resulting curve?

Two open organ pipes of fundamental frequencies $n_1$ and $n_2$ are joined in series.  The fundamental frequency of the new pipe so obtained will be

A source of sound is travelling with a velocity of $40\,km/hour$ towards an observer and emits sound of frequency $2000\,Hz$ . If the velocity of sound is $1220\,km/hour$ , what is the apparent frequency heard by the observer ..... $Hz$