Great Falls tribune. [volume] (Great Falls, Mont.) 1921-current, 1922-10-01
Barney 0ld6f@e!d says:
NOISES IN THE CAR

The variety of sounds produced by
a car that is not in need of repair is
bewildering. There is about every
sound from the dull thud of a loose
main bearing to the squeal of a rusty
spring, or from the pinking character
istic of heavy carbon deposit to the
noise due to loose body bolts or other
Tetainers holding heavy parts of the
structure in place.
The continuous sounds are the less
unpleasant. 1t is q fact that the sounds
which come from ~reciprocating parts,
such as pistons and valves, are as a
rule more unpleasant than those which
cone from rotating parts, such as
~crankshaft, camshaft and gears. A
continuous hum in a real axle is not
nearly as unpleasant as the intermlt-
tent knock due TO a loose valve tappet
or a loose connecting rod bearing. The
fact, however, that these different units
produce different sounds, makes it very
possible for the experienced ear to
Judge the point from which the sound
proceeds and an experienced mechanic
can very often tell at the first indl-
cation of sound just what point he
should reach in making his repair.
Elastic Mediums
- lUe nuEUHU ear Is OILY CdpdDle VI uc-
tecting sounds within certain ranges
That is, all sound is due to vibration
This vibration might be set up by i'm
pact, such as in a loose bearing, OIL
in a spark which is too far advanced
or it might be set up by friction. such
as in a rusty, un0iled spring. Never
theless, the effect of noise on the cal
is created by these vibrations, which
in turn, set up sound waves. The
sound waves are transmitted through
the air, which is an elastic medium.
Sound can only be transmitted
through elastic mediums. For instance
if an electric bell were operated in
vacuum, it would not be heard because
there would be no medium in which tt
form and transmit the impulses. These
sound vibrations are known as waves
and it takes these ave. a certain
length of time to travel from one point
to another. Through the air, it has
been found that sound has a velocity
independent of the pitch of the sound
or the length of the sound wave. A
very interesting example of this is, Of
course, in the instance where the bullet
from a gun outspeeds the sound made
by the explosion of the gun, the pro
jectile reaching the target before the
sound.
There are a great many sounds which
are made which no human being eve
hears, because the impulses are 81
close together that it is beyond the
power of the human ear to detect them
The upper limit of a number of vibra
tons for the average ear is about 20,
coo per second. 1t is probably yer!
fortunate for the human being that j
is impossible for him to detect sounds
above and below a certain pitch, be
cause If his range were infinite it woult
be impossible to make an automobile
which would be silent enough to b.
comfortable.
AS it is, we must work to eliminate
the intermittent noises altogether ant
to make the continuous sounds as low
as possible in our cars,-an end Il
which all our engineers are striving
When the mechanic has trained his eye
to locate certain parts by the SCUM
they are making, he might well cal
himself an expert. In many cases thu
good mechanic will not trust his owl
hearing but will make certain tests
For example, wrist pins when working
loose, say .005 inch, will knock and il
some engines it sounds very much like
a piston slap or a loose tappet. Blu
wrist pins that are loose will knocl
under load more than they will whel