over it. If you put your ear close to violin number 2 you will
hear a faint sound coming from the corresponding string in
number 2 even though you have not touched it, but you won't
hear a sound from the other three strings. You can do the same
with any string--you will always hear a faint sound from the
corresponding strings in violin number 2.
Just what has caused this curious action we will explain
now. You know that sound travels in waves just as water does
when disturbed. When we plucked the string we caused a disturbance
which produced sound waves. Air waves are not
exactly like rope waves or water waves although they follow
the same laws. When a string is vibrating in one direction it
compresses the air before it. As it moves in the other direction
the air before it is expanded. There are successive compressions
and rarefactions, then, which follow each other in regular order.
These waves travel in all directions just as Radio waves do,
so the effect on violin number 2 will be the same if it is on a
table with number 1, or under the table, or above it, or on any
side of it.
When the waves produced at number 1 reach number 2 they
naturally strike all the strings. One of the strings is in tune
with the one producing the waves so when the crest of the first
wave strikes it, the string will be pushed out of line by it, just a
trifle of course. Then when the trough follows, the string will
fly back and because of the strain put upon it, will fly back
beyond its normal position. By the time it gets back as far as
possible it is met by the crest of the second wave, and again
pushed forward. This action continues and the string on violin
number 2 vibrates in time with the string producing the waves.
What happens in the case of the other strings, why don't
they vibrate, too? The trouble appears when the very first wave
strikes it. The crest of the wave causes the other strings to
move just as it did the string that was in tune but the string
sprang back either before or after the crest of the second wave
was there to give it its second push. So the string “cut” the
waves and its motion was stopped. From this you will gather
that strings vibrate at different frequencies, depending on thickness,
length and tautness, or tension. If two strings vibrate
(oscillate) at the same frequency they are in tune.
The word “resonance” which means the same as “tuning”
will help us remember what we have talked about in the last few
paragraphs. It comes from Latin words meaning to “sound
