The audible range for a normal human being is

What is a longitudinal wave?

State whether the following statement is true or false: The velocity of sound in air is higher for higher frequencies than for lower frequencies.

State whether the following statement is true or false:
The frequency of a sounding body with a time period of $0.01 \, s$ is $100 \, Hz$.

$(a)$ What is the audible range of the average human ear?
$(b)$ Explain how ultrasound is used to clean spiral tubes and electronic components?

$A$ girl is sitting in the middle of a park of dimension $12 \,m \times 12 \,m$. On the left side of it there is a building adjoining the park and on the right side of the park,there is a road adjoining the park. $A$ sound is produced on the road by a cracker. Is it possible for the girl to hear the echo of this sound? Explain your answer.