A New or Improved Method and Means of Producing Sound.
Year: 1894

page_text: Date of Application, 5th Jan., 1894
Complete Specification Left, 3rd Nov., 1894-Accepted, 8th Dec., 1894
PROVISIONAL SPECIFICATION.
A New or Improved Method and Means of Producing Sound.
I, ALFRED GRAHAM, of No. 32 De Crespigny Park, Denmark Hill, in the
County of Surrey, Electrical Engineer, do hereby declare the nature of this
invention to be as follows:-
My invention has reference to a new method and means of producing sounds
applicable for use for telegraphic, telephonic, railway or other signalling and
Various other acoustical purposes.
In carrying out my invention an electrical circuit is formed of a battery or other
source of electricity connected to a mass of granular carbon or other material
whose electrical resistance can be varied by vibration or otherwise and then
completed through the coils of an electro-magnet either polarized or non-polarized.
In front of the electro-magnet is a diaphragm or armature sensitive to the
variations of current flowing through the electro-magnet. This diaphragm or
armature is so placed relatively or mechanically connected to the circuit of variable
resistance that any vibration imparted to it is transmitted either through a column
of air or through a material which conducts sound to the diaphragm which is in
connection with the material or parts composing the circuit of the said variable
resistance.
In the construction of the variable resistance I prefer to use the granular carbon
that is employed in telephonic transmitters. This granulated carbon is contained
in a chamber closed at one end by a diaphragm of carbon with which the granular
carbon is in electrical contact. I place this carbon resistance so that its diaphragm
can be effectively acted upon by the vibration set up by the diaphragm or armature
of the electro-magnet. Sometimes when great intensity of sound is required I
place a trumpet in front of the diaphragm of the electro-magnet and a flexible tube
coming from the carbon diaphragm is applied either to the mouth of the trumpet or
introduced in an aperture in the wall thereof.
According to another method I attach to the armature or diaphragm of the
electro-magnet a mechanical means for introducing automatically various resistances
into its circuit.
The note emitted by the apparatus may be varied by regulating the size of the
apertures either of the trumpet itself or of the tube or by adjusting their positions
relatively one to the other.
For musical purposes I may place a tube such as that of an ordinary flute
between the two diaphragms and adjust the note by varying the holes in the tube.
In connection with the above apparatus a key or make-and-break piece is inserted
in the battery circuit.
Dated this 5th day of Januar 1904
A. F. SPOONER,
124, Chancery Lane, W.C., Agent for the Applicant.
COMPLETE SPECIFICATION.
A New or Improved Method and Means of Producing Sound.
I, ALFRED GRAHAM, of No. 32 De Crespigny Park, Denmark Hill, in the
County of London, Electrical Engineer, do hereby declare the nature of this
invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
My invention bas reference to a new method and means of producing sounds
TD 071

page_text: applicable for use for telegraphic, telephonic, railway, or other signalling, and
various other acoustical purposes.
In carrying out my invention an electric circuit is formed of a battery or other
source of electricity connected to a mass of granular carbon or other material
whose electrical resistance can be varied by vibration or otherwise and then
completed through the coils of an electro-magnet either polarized or non-polarized.
In front of the electro-magnet is a diaphragm or armature sensitive to the
variations of current flowing through the electro-magnet. This diaphragm or
armature is so placed relatively or mechanically connected to the circuit of variable
resistance that any vibration imparted to it is transmitted either through a columa
of air or through a material which conducts sound vibrations to the circuit of the
said variable resistance or its diaphragm.
In the construction of the variable resistance I prefer to use the granular carbon
that is employed in telephonic transmitters. This granulated carbon is contained
in a chamber closed at one end by a diaphragm of carbon with which the granular
carbon is in electrical contact. I place this carbon resistance so that its diaphragm
can be effectively acted upon by the vibrations set up by the diaphragm or
armature of the electro-magnet. Sometimes when great intensity of sound is
required I place a trumpet in front of the diaphragm of the electro-inagnet and a
flexible tube coming from the carbon diaphragm is applied either to the mouth of
the trumpet or introduced in an aperture in the wall thereof.
The note emitted by the apparatus is capable of variation
described.
as hereinafter
For musical purposes I may place a tube such as that of an ordinary flute
between the two diaphragms and adjust the note by varying the holes in the tube.
In connection with the above apparatus a key or circuit closer is inserted in the
battery circuit.
To render my said invention clear, the same is further described with reference
to the annexed drawings wherein,
Figure 1 is a diagram illustrative of my invention, and
Figures 2, 3 and 4 are modifications thereof.
Like letters refer to like parts in all the figures.
Referring to the drawings I employ essentially, a magneto-electric or electro-
magnetic receiving device such as A which is like an ordinary telephonic receiver
having a diaphragm preferably of considerable area and of minimum thickness so
that the maximum amplitude of vibration may be obtained; a variable resistance
like an ordinary telephonic transmitter and comprising preferably carbon granules
o powder held loosely between a movable and a stationary electrode respectively;
means or arrangements for conducting the vibrations impatted to the receiver
diaphragm to the circuit of variable resistance; a battery or other source of power
such as B; and preferably but not necessarily a sound-increasing and varying
device such as D and a circuit controlling key E.
My invention consists in so constructing disposing and arranging relatively to
each other the said elements that upon completion of the circuit the vibrations set
up in the receiver diaphragm are caused to act upon the circuit of variable
resistance which in turn again acts upon the receiver diaphragm whereby a
continuous sound or musical note is emitted.
In Figure 1A is the receiving element of the apparatus consisting preferably of a
powerful U-shaped permanent magnet a carrying upon its polar extremities spools b
wound with low resistance coils. This receiving element acts upon a diaphragm c
held in a suitable case or frame d. The diaphragin c may be made of any suitable
material (in the form shown it is made of iron and is attracted directly by the
magnet a) and in front of it is the trumpet D which in the form shown operates
not only to give off the sound produced but acts by reason of the air column
enclosed within it and the position of the two elements relative to each other as
the connecting medium between the said two diaphragms. The element of variable
resistance C is shown composed of a stationary electrode f which may be a block

page_text: of carbon or other suitable conducting material having conical or other projections
from its base and mounted in a suitable case g of insulating material. In the said
case is fixed the diaphragm h which either carries, or itself forms, the movable
electrode of the apparatus and between which and the stationary electrode is
placed the body of carbon granules or powder. The sound-collecting trumpet k
is in front of the case g and operates to concentrate the sound waves upon the
diaphragm h. The element of variable resistance and the coils of the receiving
magnet a are electrically connected in series in the circuit 1, 2, 3, in which are
placed the battery B and the circuit controlling key E.
Figure 2 shows a modified form of apparatus wherein both the receiving device
and the element of variable resistance are formed as one apparatus, the two
elements being connected by a small lateral tube to the inner end of the
trumpet D. The relatively small proportion of the sound waves produced by the
vibration of the diaphragm c which will act upon the element of variable resistance
in this construction is sufficient to maintain its effectiveness. Similar results may
be obtained by employing a flexible tube coming from the element of variable
resistance (which in that case may either form part of or be separate from the
receiving device) and extending into the mouth of the receiver trumpet.
Figure 3 shows another modification wherein the vibrations of the receiving
diaphragm c are transmitted by direct mechanical connection to the circuit of
variable resistance instead of through an intermediate air column. As will be
observed the diaphragm c in this modification, itself acts as, or carries, the movable
electrode of the element of variable resistance and serves the purpose of the two
separate diaphragms used in the former arrangements. The stationary electrode f
is mounted in front of the diaphragm and is shown attached to the same frame as
that in which such diaphragm is held.
Figure 4 illustrates an arrangement for musical purposes of a flute like tube
extending between the two diaphragms. The apertures s in the tube are opened
or closed by the levers s' and operate to vary the note. The reversal of the
polarity of the battery will in this case reverse the scale of tones. This drawing
is only intended to be diagrammatic aud illustrative, it does not depict the exact
form of apparatus which may be varied without departing from the spirit of my
invention.
The sound-collecting trumpet (see Figure 1) of the element of variable
resistance is located opposite or otherwise relatively to the trumpet D of the
receiver so as to in part intercept the sound waves emanating from the diaphragm c
and cause them to act, through the diaphragm h, on the circuit of variable resist
The same or similar results are attained in the modifications shown in the
ance.
other figures.
For my purposes the best results are attained when the coils b are connected
with the battery B so as to energize the magnet a in the same direction as that
due to the permanent magnetism in it. Upon the circuit being closed by depressing
the key E the coils will be energized attracting the diaphragm c which normally
is held under tension by the said permanent magnet a. This movement of the
diaphragm c operates either through the medium of the air column in the trumpet
and the second diaphragm or directly through the compound diaphragm, to increase
or decrease the resistance in the circuit of variable resistance. This (say) increase
of the resistance decreases the strength of the battery current and causes a return
movement of the diaphragm c which, through the air column or its equivalent,
produces a return movement of the diaphragm or its equivalent with the result
of causing the movable electrode of the element of variable resistance to approach
the stationary one and decrease the resistance of the circuit. The consequent
increase of the battery current in turn increases the energy of the coils b. In this
way reciprocal effects are produced which result in the production of a continuous
sound or musical note which lasts as long as the circuit is kept closed.
The pitch, loudness, or quality of the sound produced may be varied by varying
the battery current in strength or changing its direction or by changing the forms

page_text: of the trumpets or varying the relative position of the instruments as shown for
instance by the broken lines in Figure 1 or by varying their distance apart.
The circuit closing key E may be considered as a typical representation of any
of the numerous forms of transmitting devices which will be employed in the
various applications of the apparatus.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare what I
claim is ;-
1. The method of producing continuous sound which consists in producing
vibrations of the diaphragm of an electrical receiving device and causing such
vibrations to affect an element of variable resistance included in the circuit of the
said receiver which in turn produces corresponding variations in the current flowing
in the said circuit.
2. The method of producing continuous sound which consists in producing
electrical vibrations in a closed circuit, which vibrations operate to affect the
sound-producing diaphragm of a receiving device and are communicated therefrom
either by a column of air or mechanically to, and act upon, a portion of such
circuit of variable resistance the variations in which in turn operate through the
receiving device to cause electrical vibrations of its sound-producing diaphragm.
3. An apparatus for producing continuous sound having in combination a sound-
producing diaphragmn operated by an electrical receiving device, a variable
resistance located opposite, or in a position relative to, or carried in the same
frame-work as, and acted upon by, such sound-producing diaphragın, the electrical
receiving device and the variable resistance being electrically connected in such
manner that the variations in the latter will produce corresponding variations of
the current flowing through the closed circuit of the said apparatus substantially as
described.
4. In an apparatus for producing continuous sound wherein vibrations of a sound-
producing diaphragm of an electrical receiving device are caused to act upon a
Circuit of variable resistance which in turn influences such receiving device, the
means, substantially as described, of varying the pitch, loudness, or quality of
sound produced.
5. In an apparatus for producing continuous sound wherein vibrations of a sound-
producing diaphragm of an electrical receiving device are caused to act upon a
circuit of variable resistance which in turn influences such receiving device, a single
diaphragm which acts as the diaphragm in electric connection with the movable
electrode of the element of the circuit of variable resistance and also as the
diaphragm of the receiver.
6. An apparatus for producing continuous sound having in combination an
electrical receiving device, the fixed electrode of a variable resistance, and a single
diaphragm forming part of the circuit of variable resistance between them, the
said parts being so disposed, and electrically connected in such manner, that the
vibration of the diaphragm produces corresponding variations in that part of
the circuit which is of variable resistance resulting in a continuously increasing
amount of variation of the current flowing through the apparatus.
Dated this 3rd day of November 1894.
A. F. SPOONER,
124, Chancery Lane, W.C., Agent for the Applicant.