The Bennington evening banner. (Bennington, Vt.) 19??-1961, 1916-01-25
MAKING A RECORD
Methods by Which a Phonograph
Disk Is Produced.
CATCHING THE SOUND WAVES.

| They Are First Imprisoned In Wax and
Then Transferred to Negative In
Copper, and From This Master Mold
the Records Are Obtained.
The Edison phonograph. the graphic.
phone type perfected by Bell and Tain.
ter and the gramophone type by Ber-
liner are all based on substantially the
same principle. Sound waves set up in
the air by any sound are allowed to
strike a delicately held diaphragm,
which vibrates under the impact of the
sound waves. The vibrations are made
| to leave a record on suitable me-
dium, and this sound record is used to
| perform tfis inverse operation when 1t
is required to reproduce recorded
| sounds-that Is, the record is made to
vibrate a sensitive diaphragm and set
up in the air particular waves, which
convey to tho ear the impression Of
sound,
Tho differences In the systems are in
| the way in which the vibrations are ru-
| corded. The disk record, which made
the machine popular, was first manu-
factured in the United States in 1897
improvements In the machine and in
the needles followed.
To make n rramonIlone record n nor.
son sings before tho mouth of horn,
the object OF which is to concentrate
the energy OF the sound waves upon
the recording diaphirwm. Ar the nor.
row end OF the horn !, "a the srecor,,,n,
sound box and the machine with its
attendant expert. There "a n screen
between singer and operator 20 cuard
the secrets of the sounJ. box. on. the
farther side OF the scraep. 1s 81 hor,.
zontaI toble carrying a way tahIet
rotated beneath, the recording sound
boy at a uniform speed. .usua,lv ahout
seyenty-six revolutions. ,,er minute. A
the table rotates it travels latera,lv NJ
uniform spced and tha wax tablet
IL TINS caused 70 travel slowly under
tho stationary recorilinp hoy The
sappl,ire cutting noint Is lowered so
as to enter tho way three and ouc.ba,f
70 four ono -thousan,lths Of m inch. and
as tho machine rms II cuts n fine spiral
groove. running from the edge TO the
center. The construction of the sound
boxsis secret. MS is the composition of
the wax tablet. fW sl
The next step in the process is the
reproduction OF the record as a mega.
tive in copper. The wax is busted with
graphite and worked into the grooves
with a badger brush to make It elec.
tro-conductiyc; then it is lowered into
an clectrolytic bath OF copper salt solus
tion. The wax is kept in continuous
motion i'm the bath until the copper
shell is nlne-tenths Of millimeter IN
thickness.
This negative is n master. md from
this a few commercial samples can be
pressed to test the quality Of the rec.
ord. The manufacturers. however.
wish to make thousands OF copies
without hurting their master. there.
fore they make duplicates of their
master hv taking impressions in wax
comnosition from which WORKING mat.
r,cos ore n,oao Tbcn conner sbcl,s
oro ohta;ned from thoso IN tbo aama
nav rho conror sholl 60 ,ber hac,.ad
hv hross n,ate oro.ba,f inch IN tb,cl.
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