Blackfoot news. (Blackfoot, Idaho) 1891-1902, 1898-11-19
SLIGHTEST NOISE IS REVEALED
TO THE EYE.
kakes Waves of LiGht-Projeoted to .
Screen and shown In Highly MAgai-
ned Form-Is Similar to Photography
Says Prof. Webster.

lessor Webster advanced the question,
How loud is sound?" When NO one
was able to answer he brought into
view an apparatus which served as an
absolute standard of comparison.
Hereafter il will be possible to say
lust how loud any sound may be, not
by guess work. but by means of waves
made by reflected light Incidentally,
Professor Webster remarked that with
his instrument it may be possible to
shase the echo to the source and find
sut all about it: that modified form
sf the instrument might be installed
On shipboard to be used to denote the
approach Of other vessels.
The mechanism by which Professor
Webster's machine records sound
ready for measurement is comparative
" simple. 1t consists Of set of NOV
able mirrors and prisms which act in
conjunction with diaphragm. One of
he principles involved in this part of
The process is hundreds of years old.
and was discovered by Sir Isaac New
ton. To illustrate it suppose that light
is admitted through pin hole shutter
into a dark room. Introduce into the
panel of light any opaque body, as
knife blade for example, and observe
the shadow which 1t casts on a white
screen, we shall see that the edges of
the shadow are fringed with colored
light. The light in passing by the edge
n roy NJ rb1 10
Or a bubble of air In glass is in each
case affected the same way. This is
because light always is infected, or,
more popularity speaking, refracted,
when it passes by the edges OF bodies.
But 1t is rarely observed in ordinary
circumstances, because when light
comes from various directions the coll
ors composing 1t overlap and are re-
iuced to whiteness. Any transparent
substance of excessive thinness rede7es
brilliant colors. Examples are seen in
thin laminas of air occupying cracks
in glass and ice, and the interstices be-
tween plates of mica, also in thin films
of oil on water and alcohol on glass,
but most remarkably In soapy water
blown into thin bubbles.
The same effect is produced If lens
Of slight convexity is laid on a plane
lens, and the two, after being placed
together by screw, are viewed by re-
fected light. Rings of color may be
seen ranged around the point of con-
tact. The smallest rings are broadcast
and most brilliant, and each one con-
tains the colors OF the spectrum in
their order. These are commonly cali
ed Nevton's rings, because Sir Isaac
Newton first investigated their phe-
nomena. This principle of infection
then, and modification of the instru-
ment used in producing Newton's
rings, are used in the new apparatus
for measuring sound. Within a small
square box Professor Webster has
placed several mirrors and prisms in
such manner that Newton's rings
will be projected against moving SEN
sitive Photographic plate. On one side
Of the box Is a globe-shaped resonator,
inside of which is sensitive dia-
phragm to vibrate. On the inner side
Of the diaphragm is attached small
circular mirror weighing a fraction of
gram. When sound, however
slight, enters the resonator or receiver
of the instrument, the diaphragm. and
consequently the small mirror vi
brates backward and forward. and a
small beam Of light is sent careeninx
about among the other mirrors and
he n fg L.
solve itself into series Of colored
fringes. These fringes are projected
through series of Sits in a screen
until by the time the light reaches the
Photographic plate 1t takes the form
OF waving line. This waving lin.
Is projected on a screen by means of
lantern, and may be viewed, II nee
essary, by a number Of persons at
once, as during the meeting OF the
American Association for the Advance
ment Of Science. SO. as Professor
Webster jocularly remarked, deaf
man easily might distinguish the DIFF
ference between the sounds, while a
blind man could not.
Some really startling results were
shown on the screen. Thus the yibra-
lions produced by tuning fork were
shown in the form of regular waves
across the screen. Some vowel sounds
projected into the receiver were do
picted In an irregular, waving line
showing that 1T Is impossible for snv
person to hold the voice evenly while
pronouncing letter or word. This is
a point for singers and musicians gem
orally to ponder over. A draft In the
room produced an effect which result
ed In series Of rather irregular curves
having downward trend. Silence
manifested itself in a series Of regular
fine waving lines. Ability to hear or
see silence might occasion some sur
prise, but the record proved simply
that there were sounds in the atmos-
phere which the human ear could not
hear Lord Reylelgb after some ex-
perimentation, declared that we are
capable OF hearing sounds Of an ipten-
sity less than one-millIoneth of an at
mosphere. Some idea Of the capabiI-
tiles OF this new instrument may be
gained from the fact that the little
mirror mentioned above will move