Sound - Mr Thou

Will there be sound if there is a vibrating source?
Is the speed of sound in air always 330 m/s?
If the obstruction is considerably small, will there still be an echo?
If sound strikes a soft surface, will there be a reflection that forms an echo?
If sound travels in all directions, why don’t we consider the sound that reflects off the floor/ground that we are standing on when we use the formula (speed = distance/time) to find either the speed of sound or time taken by the echoes?
What is a natural frequency of an object?
What is a resonance?
If a dolphin emits ultrasound for echolocation, what animal will emit infrasound? Are there any advantages of using infrasound compared to ultrasound?

Examiner likes to ask questions that deal with the following:

Identify the concept of sound can be broken down into 3 parts – the production, the transmission and the reflection/absorption.
Explain how sound is transmitted in a medium (solid, liquid and gas) between the source and the receiver.
Explain how sound is produced.
Calculate the time difference between subsequent echoes in a scenario of a cliff or a man standing between two walls.
Calculate the depth of an ocean using the concept of an echo.
Explain the attenuation of sound as it travels in the a medium. Popular scenario is the reduction of sound intensity in a graph that plotted for a sonar to determine the depth of an ocean.