Ultrasonic waves are those waves

Mention the audible frequency range for humans.

The wavelength of sound in any gas depends upon

If the density of oxygen is $16$ times that of hydrogen,what will be the ratio of their corresponding velocities of sound waves?

$A$ metal rod of $1 \; m$ length is dropped vertically onto a hard metal floor. Using an oscilloscope,it is determined that the impact produces a longitudinal wave of $1.2 \; kHz$ frequency. The speed of sound in the metal rod is: (in $; m/s$)

$A$ car is moving with a speed of $72 \,km/h$ towards a hill. The car blows its horn at a distance of $1800 \,m$ from the hill. If the echo is heard after $10 \,s$, the speed of sound (in $m/s$) is: