IMPROVEMENTS IN THE MANUFACTURE AND USE OF PARABOLICAL APPARATUS FOR ACOUSTIC PURPOSES
Year: 1880

page_text: LETTERS PATENT to Frank Wirth, of the Firm of Wirth and Company, Patent
Solicitors, at Frankfort on the Main, in the Empire of Germany, for an
Invention of "IMPROVEMENTS IN THE MANUFACTURE AND USE OF PARABOLICAL
APPARATUS FOR ACOUSTIC PURPOSES." A communication from Adolph Rettig,
Barrister, of Saarbrücken, in the Empire of Germany.
PROVISIONAL SPECIFICATION left by the said Frank Wirth at the Office
of the Commissioners of Patents on the 9th March 1880.
FRANK WIRTH, of the Firm of Wirth and Company, Patent Solicitors, at Frankfort
on the Main, in the Empire of Germany. "IMPROVEMENTS IN THE MANU-
FACTURE AND USE OF PARABOLICAL APPARATUS FOR ACOUSTIC PURPOSES." A
communication from Adolph Rettig, Barrister, of Saarbrücken, in the Empire of
Germany.
This Invention has for its object the practical use of parabolical apparatus for
acoustic purposes. Any parabola can be used for this purpose, the shape and size
of the apparatus varying according to circumstances. As a rule the sound is
conducted to the ear by means of a suitable pipe. If the sound conducting pipe
is to be situated behind the parabola the crown or vertex of the latter is cut off,
and a conical pipe piece attached, to which in its turn the tubing is attached. If
the crown is cut off in such a manner that the focus of the parabola falls within
the conical pipe this is enough. In order to prevent loss of sound the conical tube_
is arranged in such a manner that all waves of sound passing through the focus
are reflected into the conical tube before named; if the vertex is so cut off that the
focus falls in front of the vertex cut a second small parabola must be placed in
front of the first in such a manner that they have a common axis and the same
focus, but are placed in opposition to each other, the opening of the second parabola
corresponding to the cut off of the crown or vertex of the first. The second
parabola having the same focus as the first will catch and reflect all waves of
sound into the pipe piece of the first parabola. If the sound conducting tube is to
be situated in front of the parabola a conical conducting pipe is to be placed in the
place of the before named second parabola, and arranged in such a manner that the
.

page_text: focus of the parabola falls within the said conical conducting pipe; in this case
the cut off of the crown or vertex has no effect, so long as it is not larger than the
opening of the conical conducting pipe. A parabola can be made telescopic in order
that large sized apparatus can be more easily transported from one place to the
other; constructed in this manner the apparatus can be used with advantage for
naval, military, and similar purposes. It is preferred to construct the parabolas
with universal ball joints, so that they can be turned and fixed in the direction the
sound comes from; they can also be attached to railway carriages, and serve as a
means of communication between guard and passengers; they can also be situated
on station platforms, or attached to the rails,

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Frank Wirth in the Great Seal Patent Office on the 8th September
1880.
FRANK WIRTH, of the Firm of Wirth and Company, Patent Solicitors, at Frankfort
on the Main, in the Empire of Germany. "IMPROVEMENTS IN THE MANU-
FACTURE AND USE OF PARABOLICAL APPARATUS FOR ACOUSTIC PURPOSES." A
communication from Adolph Rettig, Barrister, of Saarbrücken, in the Empire of
Germany.
This Invention has for its object the practical use of parabolical apparatus for
acoustic purposes.
Any paraboloid can be used for this purpose, the shape and size of the apparatus
varying according to circumstances. As a rule the sound is conducted to the ear
by means of a suitable pipe. If the sound conducting pipe is to be situated behind
the paraboloid the crown or vertex of the latter is cut off, and a conical pipe piece
attached, to which in its turn the tubing is attached.. If the crown is cut off in
such a manner that the focus of the parabola falls within the conical pipe the latter
is sufficient. In order to prevent loss of sound the conical tube is arranged in such
a manner that all waves of sound passing through the focus are reflected into the
conical tube before named; if the vertex is so cut off that the focus falls in front of
the vertex cut a second small paraboloid must be placed in front of the first in
such a manner that they have a common axis and the same focus, but are placed
in opposition to each other, the opening of the second paraboloid corresponding to
the cut off of the crown or vertex of the first. The second paraboloid having the
same focus as the first will catch and reflect all waves of sound into the pipe piece
of the first paraboloid. If the sound conducting tube is to be situated in front of
the paraboloid a conical conducting pipe is to be placed in the place of the before
named second paraboloid, and arranged in such a manner that the focus of the
paraboloid falls within the said conical conducting pipe. In this case the cut off of
the crown or vertex has no effect so long as it is not larger than the opening of the
conical conducting pipe. A paraboloid can be made telescopic, in order that large
sized apparatus can be more easily transported from one place to the other;
constructed in this manner the apparatus can be used with advantage for naval,
military, and similar purposes. It is preferred to construct the paraboloids with
universal ball joints, so that they can be turned and fixed in the direction the
sound comes from; they can also be attached to railway carriages, and serve as a
means of communication between guard and passengers; they can also be situated
on station platforms or attached to the rails.
.
In the accompanying Drawings Fig. 1 shows a parabolic reflector (a-b-c), the
focus of which falls within the conical pipe, so as to dispense with any further
device for diverting the waves into the latter, the shape of the conical pipe being
such that all waves passing through the focus are reflected into the pipe; Fig. 2,
b₁, C, shows in elevation and horizontal section a parabolic reflector with a small
counter reflector placed opposite, the main reflector, and having the same focus as
the latter. In Fig. 2, b, c, the pipe-is-situated in front of the parabolic reflector;
in this case the vortex of the main parabola need not be cut off.
As only those waves have any useful effect which reach the counter reflector or
the interior of the conducting pipe the size of the main reflector is limited by this
condition. In Fig. 1 the reflector is supported in a ball joint attached to a post or
stand. If the apparatus is to be portable the stand is held in two superposed eye
bars pivoted at their other ends to a plate which may be attached to the belt,
or otherwise carried by the person using the apparatus; Fig. 3 shows, besides the
plate and eye bars, two rings placed one over the other, and by which the stand
may be supported for more convenient transport if desired. In portable apparatus
the round conducting pipe may be situated before the parabolic reflector, but

page_text: preferably behind the latter. If the conducting pipe is behind the reflector the
apparatus may be attached to a strap or belt carried by the person using it, without
necessitating a special carrying plate.
From the end of the conical round conducting pipe a conducting pipe of metal,
india-rubber, or other suitable material leads to the ear, and is provided with a
terminal or button of bone, india-rubber, or other suitable material, to be introduced
into the ear; Fig. 5 shows a short metallic conducting pipe, while Fig. 6 indicates
the shape of the button or terminal. In order to diminish the pressure on the ear
this conducting pipe is held by a short pipe fitting tightly to the conducting pipe,
and resting in a ring attached to a button, which may be fastened in a slit or
button hole of a coat or other piece of garment; Fig. 4, a, b, c, gives an example of
a holding ring and button. This device, which considerably facilitates the use
of the apparatus, serves also to retain the terminal in its proper place without
using the hands.
The greater the conducting power of the pipe the smaller is the loss of sound by
its transmission from the reflector to the ear. The reflector is generally powerful
enough to allow of the application of a pliable pipe, but where the sound must be
economised a rigid metal pipe should be used, at least for the greatest part of the
way in which the sound is to be conducted; the terminal however remains
substantially the same as for the flexible pipes. The intensity of the sound
transmitted to the ear may be diminished by using soft india rubber conducting
pipe, or by partly withdrawing the terminal from the ear, but especially by
diminishing the effective surface of the reflector; this is effected by providing the
reflector with concentric rings, which may be used together, so as to produce the
maximum reflecting surface, or which may be detached and enclosed in a casing.
By putting on one or more of the concentric rings the power of the reflector may
be varied at will to suit different circumstances. This arrangement may be utilized
to ascertain by experiment the size of reflector required for a certain effect, or for
operating at a certain distance.
The apparatus may be adapted to be attached, supported, or suspended in any
suitable position. Figs. 1 & 2 show a ball joint or spherical bearing provided with
a screw and a vertical pin pivoted in a hollow standard, so as to permit an
adjustment in all directions; Fig. 8 shows a parabolic reflector constructed in
telescope fashion, being composed of three zones, the two outer ones of which may
be put in or out of action.
This shape of reflector may not only be used for large reflectors, but also for
small instruments (for assisting a weakened hearing organ), for the use of
physicians, &c.).
For observing sounds in the interior of various bodies (auscultation) long
reflectors are most suitable.
If used on railways the apparatus may be connected with the rails, in order to
utilize the sound conducting power of the rails, the connection taking place by means
of a conductor ascending in the interior of the column which carries the parabolic
reflector. By this means the motion of a train may be heard at a great distance.
In order to make observations on railways from the interior of a building the
sound conducting pipe is placed in the column, and continued on any suitable way
to the observatory. Fig. 9 illustrates such an arrangement where the reflection can
be turned to any side by means of shafts and tooth gearing. The sound may be
made to pass at will either through the bottom of the column or through a lateral
arm (a, Fig. 9) by means of valves, for instance, such as are shown by the detail
views on Sheet II. For conducting the sound laterally a branch pipe is adapted
to the arm a, and closed by the valve when not used.
If it is desirable to observe a large field from one point, for instance, the environs
of a fortress, and the use of one large apparatus would be inconvenient or difficult
several movable or fixed reflectors may be stationed at suitable points, and
connected with the centre of observation by conducting pipes which lead to a
parabolic reflector, the front opening of which is covered by a plate having openings

page_text: provided with small cylindrical pipes which can be closed or opened, and to which
the conducting pipes are screwed or otherwise attached. The parabolic collector
receives the sound transmitted by the conducting pipes and reflects the sound waves
into a common conducting pipe.
For conducting sound to great distances several reflectors may be applied in
succession, the first transmitting the sound through a pipe to the second, the second
to the third, and so on.
Fig. 10 illustrates the application of parabolic reflectors or collectors to railway
trains for establishing a communication between the passengers and the conductor
or the engine-driver. Each carriage has a reflector in the ceiling of each com-
partment, and the reflectors are connected by pipes with a parabolic collector in
front of the carriage, the opening of which is covered by a plate, and which also
communicates by a pipe with a parabolic reflector at the back of the carriage, the
latter being connected by a pipe with the collector situated in front of the following
carriage.
The apparatus may be used as a telephone in various places; for instance, for
establishing communication between different parts of a fortified place, or of a mine,
or of a building, &c. If persons at different places are connected with one person
(central station) the latter has a parabolic reflector communicating with his ear,
and closed by a plate, to which are joined several pipes leading to the different
speakers, each of the said pipes being attached or removed at will. The conducting
pipes for the various speakers may be joined to a plate, upon which the parabolic
collector is movable, so that it can be placed before any of the sound conducting
pipes. It is not necessary to speak direct into the parabolic reflector used for
transmitting speech. For auscultation the wide end of a parabolic reflector may
be placed directly upon the body to be observed, and metallic sound conducting
pipes are most suitable for this purpose. The fact that sound waves can be
collected and transmitted by means of parabolic reflectors is known, I do not
therefore claim the general principle, but the special means and forms of apparatus
for its practical application.
1. The fundamental forms of apparatus illustrated by Figs. 1 & 2.
2. The various constructions for receiving and collecting paraboloids, substantially
as described.
3. The various auxiliary appliances comprising hollow columns, ball joints,
carrying plate and button shaped device for attaching the conducting pipe to
garments, in combination with sound reflectors, substantially as described.
4. A sound reflector constructed in telescope fashion, substantially as described.
5. The adaptations of the apparatus for military purposes, for use on railways,
and in railway trains, substantially as described.
6. The apparatus for transmitting speech by means of parabolic reflectors
(telephonic arrangement), substantially as described.
7. The method of regulating the power of parabolic reflectors by means of
movable concentric rings, applied before the front opening of the paraboloid,
substantially as described.
In witness whereof, I, the said Frank Wirth, have hereunto set my hand and
seal this 1st day of September. A.D. 1880.