It makes a humming noise.
When lightning passes through the air, what noise is made?
A noise which we call thunder.
How can a murmur be produced?
When sounds, too faint to be heard separately, are united, they produce a murmur.
Where may we hear a murmur?
We may hear a murmur from the brook, as its waves flow over the pebbles, and from the wind, as it passes through the trees.
When a sound is heard but once, what is it called?
It is called a noise.
When sounds are made at irregular intervals, what are they called?