The waves of sound move in every direction from the place where the noise is made.
Why do we put both hands around the mouth when we call to a person at a distance from us?
We do so to keep the waves of sound more together.
Does it make the voice louder?
It does make the voice louder.
What instrument has been made so as to operate in the same way?
The speaking-trumpet, as is shown in [Fig. 24].
Fig. 24.
Of what use are speaking-trumpets?