Assertion: A closed pipe and an open pipe cannot be in resonance with the same tuning fork, if the length of the closed pipe is integral multiple of the length of the open pipe.

Reason: An odd number is not divisible by an even number.

Assertion: No Doppler effect will be observed in sound when source and observer are moving with the same speed.

Reason: Doppler effect may be due to change in wavelength also.

Assertion: Ultrasonic is the acoustic analogue of ultraviolet radiation.

Reason: Ultraviolet rays do not produce visual sensations while ultrasonic waves are not heard by the human ear.

Assertion: Longitudinal waves are called pressure waves.

Reason: Propagation of longitudinal waves through a medium involves changes in pressure.

Assertion: If two people talk simultaneously and each creates a sound level of $60 \mathrm{dB}$ at a point $P$, then total sound level at the point $P$ is $120 \mathrm{dB}$.

Reason: Sound level is defined on a non-linear scale.

Assertion: Doppler effect does not depend upon the distance between source and observer.

Reason: If source and observer are moving with same velocities, then no Doppler effect will be observed.

Assertion: Speed of sound in ${\mathrm{O}}_2$ gas at temperature $T$ is $v$. If temperature is increased to $2T$, the molecular oxygen breaks into atomic oxygen. Then, the speed of sound under these conditions will become $2v$.

Reason: With the increase in humidity in the air, speed of sound increases.

Assertion: Fundamental frequency of a narrow organ pipe is more than a broad diameter organ pipe of the same length.

Reason: If we apply Laplace end correction, then the fundamental frequency of a closed organ pipe is more than $\frac{v}{4l}$.

Assertion: If a stretched wire fixed at both ends is vibrating in its second overtone mode, then the total number of nodes and antinodes are four each.

Reason: Number of antinodes is equal to the number of loops.