Improvements in Electric Sound-producing Devices.
Year: 1897

page_text: Date of Application, 19th Mar., 1897-Accepted, 5th June, 1897
COMPLETE SPECIFICATION.
Improvements in Electric Sound-producing Devices.
A communication by JOSEPH A. G. TRUDEAU, of 329, Kent Street, Ottawa, in
the Dominion of Canada, Electrical Engineer.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of The Agency for
Foreign Patent Solicitors, 6 Lord Street, Liverpool, and 6, Bank Street,
Manchester, both in the County of Lancaster, 118 New Street, Birmingham, in
the County of Warwick, and 322 High Holborn in the County of Middlesex,
Civil 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 :-
This invention relates to sound-producing devices in the nature of a horn or
whistle, and consists essentially of a magnet or magnets energised by an alternating
current and approximated to a plate of iron, steel, or other metal, forming the
bottom of a horn or whistle, through which magnets the electric current thus
generated, is transmitted and regulated, as to sound in proportion to the electric
power utilised.
The invention is more particularly designed for use where a large volume of
sound is required, as for instance, for factory whistles, fog horns, railway and boat
whistles, fire alarms, and the like, and to adapt the device to such uses it is
essential that there be both a powerful current of electricity and a rapid reversal
or alternation thereof.
The attainment of the result upon a satisfactory commercial basis requires the
employment of an alternating current. By varying the frequency of alternation,
that is the rate per second or minute, and consequently the rate of vibration of
the bottom or vibrating part of the instrument, the pitch of the note produced may
be varied as desired, other conditions remaining unchanged. The note may also be
changed in quality by varying the distance between the vibrating parts and the
magnet poles, of which latter there may be any desired number. So too, separate
vibrating parts may be employed and caused to vibrate in unison for the purpose
of producing composite sounds, or of varying the sound, and means may be provided
for controlling the current of any or all of the magnets employed. The possible
applications of the device are very numerous, and some of them will be hereinafter
mentioned.
Referring now to the drawings:-
Figure 1 is a sectional view of a fog horn or signal constructed in accordance
with the invention;
Figure 2, a perspective view of a whistle or sound-producing device suitable for
factories;
Figure 3, a face view or side elevation of the same, with one vibratory part
partially broken away;
Figure 4, a vertical transverse section through the same.
In the drawing, A indicates an alternating electric generator, a the outgoing
line, and b the return line of said generator, and B a fog horn or whistle included
in the circuit of the alternator A. This fog horn or whistle consists essentially of
a box-like shell or body e within which is placed an electro-magnet, or a series of
electro-magnets, d, the poles of which protrude beyond the bobbins or spools, and
are brought to a common plane by careful dressing of their ends. The magnets
should be so wound as to produce like poles in said common plane.
017
Facing the

page_text: poles of the electro magnets d, and in close proximity thereto, but not in contact
therewith, is a vibratory part e of iron, steel or other magnetic material, or of some-
non-magnetic substance bearing armatures of soft iron facing the poles of the
magnets. indicates a horn or funnel, preferably provided with a cylindrical'
section at its inner end, screw threaded to engage with or screw upon the box-like
body of the instrument, so that by turning and thus adjusting the horn or funnel,.
the sound produced by the instrument may be varied.
The operation of the device will be readily understood. Upon the operation of
the generator A, a series of electrical impulses will be produced in the circuit a b
and in the included magnet windings, alternately in opposite directions. These
current impulses will energise the magnets d for minute periods, giving to the
poles facing the vibratory parts first a north and then a south polarity. This will
in turn cause the vibration of the vibratory parts, or molecular changes therein, or
both, resulting in the production of a loud and well defined note. This note may,
as above indicated, be varied or modified by increasing or diminishing the number
of vibrations or alternations per second; by varying the distance between the
magnet poles and the vibratory part, or by adjusting the horn or funnel with
reference to the latter. Two or more of these modes of variations may be utilised
jointly. In practice it is found important and in fact well nigh essential, to employ
a current of high frequency of alternation.
In Figures 2, 3 and 4, the apparatus has been represented in a form suitable for
factory use, the magnets d in this case being supported in a suitable upright frame g
provided with a roof h, and two vibratory parts e being employed. The cores of
the magnets extend through and protrude beyond their windings or helices, producing
a pole at either end, and one vibratory part is arranged opposite the poles at one
end and the other opposite those at the other end, as best seen in Figure 4. As before
explained, the windings should be such as to cause all those poles in one plane to
be of like polarity, so that all shall act simultaneously and with like effect up on
the vibratory part facing them. The form of the apparatus may of course vary as
desired.
By the construction above set forth, my correspondent has been enabled to
produce instruments capable of producing an enormous volume of sound, which may
be heard at distances hitherto impracticable with any instrument in the nature of a
horn or whistle, of which he has knowledge. For fog horns, which often require to
be located in places difficult of access, or at times wholly inaccessible, or which are
necessary to sailing vessels and craft devoid of steam or of air forcing devices, this
invention affords an invaluable means of signalling. For like reasons it is of special
usefulness for mills operated by water; for electric railway systems; for producing
warning signals at railway crossings; and for all similar uses. The facility with
which wires may be run into and throughout a building, and current taken from
general supply mains, also renders the device readily applicable with horns or
whistles of small size, to the purpose of calling or signalling systems in buildings,
as for instance, in hotels, office buildings and the like; or for fire alarm systems,
either general or local. It may also be employed in connection with time
measuring devices to give signals at stated hours or periods, or with thermostats to
indicate variations in temperature beyond predetermined points, or in connection
with barometers, thermometers, water ganges, and analogous instruments, and
generally in all places where electric bells, annunciators and the like have hitherto
been employed.
Having now particularly described and ascertained the nature of the said inven
tion and in what manner the same is to be performed, as communicated to me by
my foreign correspondent, I declare that what I claim is :-
1. A sound-producing device comprising a generator of alternating electric
currents, an electric magnet or magnets included in the circuit of said generator
and a vibratory part facing the pole or poles of said magnet or magnets and having
a magnetic portion opposed to said pole or poles, substantially as set forth.

page_text: 2. A sound-producing device consisting of a generator of alternating currents of
electricity, an electro magnet or magnets included in the circuit of said generator,
a magnetic vibratory part facing the pole or poles of said magnets and adapted to
be thrown into vibration by variations in the polarity of the latter, and a pipe or
funnel adapted to gather and to direct the sound waves produced.
3. In combination with a suitable support, a magnet or magnets d carried
thereby, a vibratory part e facing said magnets, and a pipe or funnel ƒ adjustable
relatively to the vibratory part substantially as described and shown.
Dated this 18th der of March 1897
WM. P. THOMPSON & Co.,
Agents.