Of the following,the one which emits a sound of higher pitch is:

In a city,the sound intensity level increases uniformly by about $1 \ dB$ annually. How many years will it take for the intensity of sound to become double?

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

$A$ source of sound emits $200\pi \text{ W}$ power which is uniformly distributed over a sphere of $10 \text{ m}$ radius. What is the loudness of sound on the surface of the sphere?

$A$ hearing test is conducted on an aged person. It is found that her threshold of hearing is $20 \, dB$ at $1 \, kHz$ and it rises linearly with frequency to $60 \, dB$ at $9 \, kHz$. The minimum intensity of sound that the person can hear at $5 \, kHz$ is

The note "Saa" on the Sarod and the Sitar have the same pitch. The property of sound that is most important in distinguishing between the two instruments is