An Improved Topophone or Apparatus for Localising or Determining the Direction of Sound Producing Instruments.
Year: 1888

page_text: Date of Application, 4th Feb., 1888
Complete Specification Left, 31st Oct., 1888
Complete Specification Accepted, ith Dec., 1838
An Improved Topophone or Apparatus for Localising or Determining
the Direction of Sound Producing Instruments.
1, CHARLES MARIE MICHEL DE GOYON, Duc de Feltre, of Paris, France, do hereby
declare the nature of this invention to be as follows:—
My Invention relates to an improved topophone or apparatus for localizing or
determining the direction of origin of all kinds of acoustic signals particularly at sea
and in a foggy condition of the atmosphere such that ship's lights cannot be seen,
except at too short a distance to avoid collisions, when steaming at full speed.
It has been sought to obviate this danger, by the employment of the siren which
cannot, however, be relied on alone, as it often happens that two vessels in commu-
nication with each other in foggy weather by means of a siren, are unable to determine
either their relative positions or courses, each being liable to be deceived in the
direction whence the sound of the other's siren proceeds. This is due to the fact
that in the obscurity of a thick fog, the sense of hearing uncorrected or unaided by
that of sight becomes perverted, so that sounds appear to come from a totally
different direction to the true one. This oral error is consequently apt to lead to
results which might be avoided were the captain of a vessel able to determine with
absolute precision the direction whence the sound of the siren on another vessel
emanates.
The present invention is based on the employment of a resonator capable of being
rotated in azimuth, so that when the mouth of the resonator is directed towards the
direction whence the sound proceeds, the resonator will respond if it has been attuned
to the pitch of this sound or one of its harmonics, and if the vibrations of the
resonator be transmitted to a suitable indicator the latter will denote by the maximun
indication afforded, when the month of the resonator is directed to the true point
whence the sound is emitted. It will therefore only be necessary to observe the
bearing position of the resonator relatively to the course of the vessel to ascertain the
true bearing of the direction whence the sound emanates. The obliteration of
the sense of hearing is in this manner corrected by the sense of sight which under
such circumstances is incapable of error, the human ear which is subject to external
impressions through the brain being replaced by the resonator which is entirely
unaffected by such influences.

page_text: The invention comprises three essential parts z.-the sound receiver; the trans-
mitter of the vibrations of the receiver; and the indicator denoting that position of
the receiver at which the vibrations attain their maximum.
Reference is to be had to the accompanying drawings forming part of this specifica-
tion wherein figure 1 represents one of the combinations by which the invention may
be carried into effect. As the ships sirens now in use do not all produce the same
fundamental tone, it is preferred to employ a series of resonators a be placed one
above the other in the same vertical plane (three being represented in the drawing
although any other number may be employed) each corresponding to one of the said
fundamental tones or to one of their harmonics. The resonators are mounted upon a
support & mounted on a hollow column h and are each provided with a capsule or
chamber containing a membrane or diaphragm vibrating in unison with the
resonator, the whole constituting the receiver."
Instead of simple resonators producing a single sound as shown, Koenigs cylindrical
resonators producing sounds of variable pitch may be used which may be brought in
unison at will with several harmonics of the same fundamental tone.
Each of the capsules or boxes e, is put in communication by means of a branch
tube with a main tube fof rigid metal which communicates with the tubular axis h
upon which the receiver or set of resonators may be rotated..
The receiver support d is fixed in a metal socket piece g screwed to the top of
tube and the latter turns freely in a bearing i fixed at a convenient height above the
deck in an exposed position (such as on the captains bridge j for example), the lower
end of the tube turning in a footstep 7 fixed on a table and provided with a
stuffing box and enclosing a chamber with which the tubes m and n communicate.
Upon the tube is keyed a disc having a handle a in the same vertical plane with
the axes of the mouths of the resonators. In this same vertical plane and upon the
upper face of disc r is diametrically marked an arrow whose point is above the centre
of handle . A pointer y fixed on a support z is adjusted in a fore and aft direction
parallel to the longitudinal axis of the vessel, so that when the arrow on the disc vis
similarly adjusted it will be in a line with the pointer y.
When any one of the resonators vibrates, the vibrations are transmitted by the
diaphragm of the corresponding capsule or box e to the gazeous fluid contained in
tubes f. This fluid may consist of illuminating gas supplied by pipe m from a
reservoir at a constant pressure, and in this case the vibrations would be indicated
by a manometric or sensitive flame as shown, the gas passing through a metal pipe n
connected to the chamber within the footstep and provided with a cock 0, to a
burner having a very small circular orifice and enclosed in a lantern q.
??
The flame produced at the burner will be elongated by the vibrations of the receiver
being transmitted to the gas, this elongation attaining its maximum when the receiver
or series of resonators is directed towards the source of the sound under observation
which is done by rotating the dise v together with the receiver by means of the
handle until the maximum elongation of the flame is attained.
The angle which the fixed pointer y then forms with the arrow on the disc v will
give the direction of the origin of the sound relatively to the course of the vessel.
In order to ascertain when the maximum elongation of the flame is attained, a
prism or mirror r mounted on a vertical axis and rotated through bevel gear from a
handles is employed. In this mirror, the image of the flame has the appearance of
a luminous band more or less tongued whose variable height may be read off upon a
graduated scale (suspended from the support u a little to the rear so as not to eclipse
the reflection of the flame in the mirror) whereby the instant when the disc v has been
turned to the proper direction, may be ascertained.
The combination of the fixed pointer y, tube n, burner p, mirror v and scale
constitutes one of the indicators which may be employed, but the instrument may be
varied in either of the two following ways; First instead of illuminating gas, atmo
spheric air contained in the tubes fhn may be employed as a transmitting medium
(in which case the tube n would be dispensed with) the vibrations of the air contained
in these tubes being transmitted to the index of a sphygmograph, and the. maximum

page_text: む
notion of this instrument indicating when the disc has been turned to indicate the
true bearings of the sound under observation; Secondly, again employing atmospheric
air, the vibrations of this medium may be transmitted to an electric commutator acting
on a series of rheostats introduced into the circuit of a voltaic battery of which the
current by its variable intensity as denoted by the galvanometer will indicate when the
disc and resonators are properly adjusted to the sound under observation.
The mouths of the resonators may be made trumpet shaped, as indicated in dotted
lines, instead of cylindrical in order the better to collect the sound-waves. More-
over, in order to render sensible the vibrations of one or more resonators situated at
a very great distance from the source of the sound under observation and to increase
the distance at which the vibrations of the resonators may be perceived, the well-
known properties of the microphone and telephone may be utilized. For this
purpose, the resonator or resonators would be mounted on the supporting base, or
sounding board of a microphone which would be isolated, as usual, in order that this
instrument may respond only to the influence of the resonators.
The combination of resonators and microphone is mounted on a vertical axis so that
it may be rotated in azimuth as in the former case. The terminals of the microphone
are connected to the telephonic receiver, and in the circuit is also included a battery
the intensity of whose current is proportionate to the length of the circuit connecting
the transmitting and receiving parts of the instrument. "By these means, the highly
magnified vibrations of the resonators may be audibly perceived at the telephonic
receiver, the maximum intensity of the sound thus perceived, corresponding to the
instant when the mouth of the resonators are exactly directed towards the source of
the sound under observation.
In order to enable the sense of sight to be substituted for that of hearing in the
search for the direction of the sound, the telephonic receiver may be closed by a cover
fixed upon the car piece, and the space comprised between the diaphragm of the
receiver, and this cover may be in communication with the manometric or sensitive
flame placed in front of a rotating mirror. The telephonic receiver thus acts upon the
flame in the same way as, and in lieu of, the manometric chamber applied to the
resonator in the arrangement shewn in figure 1.
It should be observed that in the above described apparatus, any suitable kind of
microphonic, telephonic, or micro-telephonic transmitting or receiving apparatus may
be employed.
When it is required to collect and indicate only the vibrations of a sound of
determinate pitch, they should be collected as above explained, by means of a resonator
attuned to this sound, but if there is no necessity to distinguish a particular sound
amongst others of different pitch or nature, the use of a resonator is not indispensable.
Experience has shewn that by placing in the direction of origin of the sound a
microphone having sufficiently numerous points of contact, the vibrations of the
microphone produced by this sound, and transmitted to the telephonic receiver by
means of an electric current, are indicated by the manometric or sensitive flame
without recourse being had to the use of a resonator. The amplitude of theso
vibrations is inversely proportional to the distance of the microphone from the
source of the sound, but other things being equal this amplitude and consequently the
movement of the manometric or sensitive flame are at their maximum when the
microphone is exactly turned in the direction of the source of the sound.
I will now describe in detail, the microphonic and telephonic combination for the
reception and transmission of sound-waves and a galvanometric indicator for denoting
their intensity.
Referring to the drawings, figure 2 shews in plan, a diagram of an instrument in
which a single movable microphone is employed. Figure 3 is a similar view of the
same instrument with the addition of a telephonic receiver. Figure 4 is a diagram
of a multiple instrument in which several stationary microphones are employed. In
these figures, the same letters indicate the same parts.
In figures 2 and 3, a is the base or sound-board and the carbon pencils of the
microphone capable of being rotated in azimuth upon an axis c on which it is mounted

page_text: by brackets d. The microphone is connected in circuit X with a battery e and
galvanometer fand in the case of figure 3; with a telephonic receiver g. Experience
has shewn that the effect of waves of sound upon the microphone is not only inversely
proportional to the distance of the source of sound, but also that this effect is less
powerful, according as the angle of incidence of the sound is more acute and attains
its maximum when the sound strikes perpendicularly against the board a.
In order to determine whence a sound emanates, it is only necessary to rotate the
microphone in azimuth until the sound perceived in the telephonic receiver g or the
deflection of the galvanometer needle, attains its maximum.
If, for example, this maximum occurs when the microphone is turned to the
position at it will be known that the direction of the sound is then normal to the
microphone, as indicated by the arrow Y.
Instead of a movable microphone, a number of fixed microphones facing towards
different points of the compass may be employed, as indicated, for example, in
figure wherein four microphones a a² a³ at are represented as facing the four
cardinal points, the carbon pencils of each microphone being, connected up in a
separate circuit (X¹ X*X*X) with a battery (e¹ e² e³¹) and galvanometer (ſ¹ƒª²ƒ³ ƒ^)
as before.
With such an arrangement, if a sound received causes the needle of only one of
the galvanometers to be deflected it will be known that the direction in which the
sound arrives is perpendicular to the corresponding microphone. Thus, if for example,
the needle of the galvanometer 1 only be deflected, the sound emanates from the
direction of the arrow W, but if two of the galvanometer needles be deflected, it will
be known that the sound strikes at a certain angle upon two out of the four
microphones, and that if the deflection of the two galvanometers is equal, the angle of
incidence of the sound upon the two microphones is also equal and therefore, emanates
from a source situated in the line bisecting the angle at which the two microphones
are placed relatively to each other. Thus, if for example, the galvanometers f1f2
are deflected simultaneously and to the same extent, it will be known that the sound
emanates from the direction of the arrow S. W. which is in the line bisecting the
angle m, n, p
If, on the other hand, the deflection of the galvanometer needles is unequal, it will
be known that the source of the sound is towards the one or other side of the
bisecting line, for instance, if the deflection of f2 is greater than that of f1, it will
be known that the sound emanates from a point situated between the directions S. W.
and S., and between the directions S. W. and W. if the deflection of the needle f¹ be
the greater.
By employing a greater number of microphones, a much more precise determina-
tion of the direction whence the sound emanates may be obtained, and to this end a
multiple instrument composed of say, 8, 12 or 16 microphones arranged in the form
of a single polygon, or of several superposed polygons may be employed. It will also
be understood that the arrangement of the apparatus may be modified in practical
details without varying the nature of the invention; for example, the circuits may
comprise any number of galvanometers if it is desired that the indications may be
observed in different parts of the ship. Moreover, the deflections of the galvanometer
needles may be graphically registered by any suitable known means, or the galvano-
metric indicator may be replaced by any equivalent recording apparatus furnishing
graphic indications, such, for example, as the well known Siphon Recorder.

page_text: An Improved Topophone or Apparatus for Localising or Determining
the Direction of Sound Producing Instruments.
1, CHARLES MARIE MICHEL DE GOYON, Duc de Feltre, of Paris, France, 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 relates to an improved topophone or apparatus for localizing or
determining the direction of origin of all kinds of acoustic signals particularly at sea
and in a foggy condition of the atmosphere such that ship's lights cannot be seen,
except at too short a distance to avoid collisions, when steaming at full speed.
It has been sought to obviate this danger, by the employment of the siren which
cannot, however, be relied on alone, as it often happens that two vessels in communi-
cation with each other in foggy weather by means of a siren, are unable to determine
either their relative positions or courses, each being liable to be deceived in the
direction whence the sound of the other's siren proceeds. This is due to the fact that
in the obscurity of a thick fog, the sense of bearing uncorrected or unaided by that
of sight becomes perverted, so that sounds appear to come from a totally different
direction to the true one. This oral error is consequently apt to lead to results which
might be avoided were the captain of a vessel able to determine with absolute precision
the direction whence the sound of the siren on another vessel emanates.
The present invention is based on the employment of a resonator capable of being
rotated in azimuth, so that when the mouth of the resonator is directed towards the
direction whence the sound proceeds, the resonator will respond if it has been attuned
to the pitch of this sound or one of its harmonics, and if the vibrations of the resonator
be transmitted to a suitable indicator the latter will denote by the maximum indication
afforded, when the mouth of the resonator is directed to the truc point whence the
sound is emitted. It will therefore only be necessary to observe the bearing position
of the resonator relatively to the course of the vessel to ascertain the true bearing of
the direction whence the sound emanates. The obliteration of the sense of hearing is
in this manner corrected by the sense of sight which under such circumstances is
incapable of error, the human car which is subject to external impressions through
the brain being replaced by the resonator which is entirely unaffected by such
influences.
The invention comprises three essential parts.viz.-the sound receiver; the transmitter
of the vibrations of the receiver; and the indicator denoting that position of the
receiver at which the vibrations attain their maximum.
Reference is to be had to the drawings left with my provisional specification wherein
figure 1 represents one of the combinations by which the invention may be carried
into effect. As the ships' sirens now in use, do not all produce the same fundamental
tone, it is preferred to employ a series of resonators a b c placed one above the other
in the same vertical plane (three being represented in the drawing although any other

page_text: number may be employed) each corresponding to one of the said fundamental tones
or to one of their harmonics. The resonators are mounted upon a support d
mounted on a hollow column hand are each provided with a capsule or chamber e
containing a membrane or diaphragm vibrating in unison with the resonator, the
whole constituting the receiver.
Instead of simple resonators producing a single sound as shown, Koenigs cylindrical
resonators producing sounds of variable pitch may be used which may be brought in
unison at will with several harmonics of the same fundamental tone.
Each of the capsules or boxes e, is put in communication by means of a branch
tube with a main tube of rigid metal which communicates with the tubular axis h
upon which the receiver or set of resonators may be rotated.
h
The receiver support d is fixed in a metal socket piece g screwed to the top of tube
and the latter turns freely in a bearing i fixed at a convenient height above the deck
in an exposed position (such as on the captains bridge for example), the lower end of
the tube turning in a foot step I fixed on a table & and provided with a stuffing box
and enclosing a chamber with which the tubes m and n communicate. Upon the
tube is keyed a disc e having a handle a in the same vertical plane with the axes of
the mouths of the resonators. In this same vertical plane and upon the upper face
of disc is diametrically marked an arrow whose point is above the centre of
handle a.
A pointer y fixed on a support is adjusted in a fore and aft direction
parallel to the longitudinal axis of the vessel, so that when the arrow on the disc is
similarly adjusted it will be in a line with the pointer y.
€
When any one of the resonators vibrates, the vibrations are transmitted by the
diaphragm of the corresponding capsule or box e to the gazeous fluid contained in
tubes fh. This fluid may consist of illuminating gas supplied by pipe m from a
reservoir at a constant pressure, and in this case the vibrations would be indicated by a
manometric or sensitive flame as shown, the gas passing through a metal pipe n
connected to the chamber within the footstep and provided with a cock o, to a
burner having a very small circular orifice and enclosed in a lantern g.
The flame produced at the burner will be elongated by the vibrations of the receiver
being transmitted to the gas, this elongation attaining its maximum when the receiver
or series of resonators is directed towards the source of the sound under observation
which is done by rotating the disc together with the receiver by means of the
handle until the maximum elongation of the flamme is attained.
The angle which the fixed pointer y then forms with the arrow on the disé v
will give the direction of the origin of the sound relatively to the course of the vessel.
In order to ascertain when the maximum elongation of the flame is attained, a
prism or mirror 7 mounted on a vertical axis and rotated through bevel gear from a
handles is employed. In this mirror, the image of the flame has the appearance of
a luminous band more or less tongued whose variable height may be read off upon a
graduated scale (suspended from the support a little to the rear so as not to eclipse
the reflection of the flame in the mirror) whereby the instant when the dise has been
turned to the proper direction, may be ascertained.
The combination of the fixed pointer y, tube n, burner p, mirror and scale t
constitutes one of the indicators which may be employed, but the instrument may be
varied in either of the two following ways; First instead of illuminating gas, atmo-
spheric air contained in the tubes fhn may be employed as a transmitting medium
(in which case the tube n would be dispensed with) the vibrations of the air contained
in these tubes being transmitted to the index of a sphygmograph, and the maximum
motion of this instrument indicating when the disc has been turned to indicate the
true, bearings of the sound under observation. Secondly, again employing atmo-
pheric air, the vibrations of this medium may be transmitted to an electric commutator
acting on a series of rheostats introduced into the circuit of a voltaic battery of
which the current by its variable intensity as denoted by the galvanometer will
indicate when the disc and resonators are properly adjusted to the sound under
observation.
The mouths of the resonators may be made trumpet shaped, as indicated in dotted

page_text: lines, instead of cylindrical, in order the better to collect the sound-waves. Moreover,
in order to render sensible the vibrations of one or more resonators situated at a very
great distance from the source of the sound under observation and to increase the
distance at which the vibrations of the resonators may be perceived, the well-known
properties of the microphone and telephone may be utilized. For this purpose, the
resonator or resonators would be mounted on the supporting base or sounding board
of a microphone which would be isolated, as usual, in order that this instrument may
respond only to the influence of the resonators.
The combination of resonators and microphone is mounted on a vertical axis so that
it may be rotated in azimuth as in the former case. The terminals of the microphone
are connected to the telephonic receiver, and in the circuit is also included a battery
the intensity of whose current is.proportionate to the length of the circuit connecting
the transmitting and receiving parts of the instrument. By these means, the highly
magnified vibrations of the resonators may be audibly perceived at the telephonic
receiver, the maximum intensity of the sound thus perceived, corresponding to the
instant when the mouths of the resonators are exactly directed towards the source of
the sound under observation.
In order to enable the sense of sight to be substituted for that of hearing in the
search for the direction of the sound, the telephonic receiver may be closed by a cover
fixed upon the ear piece, and the space comprised between the diaphragm of the
receiver, and this cover may be in communication with the manometric or sensitive
flame placed in front of a rotating mirror. The telephonic receiver thus acts upon the
flame in the same way as, and in lieu of, the manometric chamber applied to the
resonator in the arrangement shewn in figure 1.
It should be observed that in the above described apparatus, any suitable kind of
microphonic, telephonic, or micro-telephonic transmitting or receiving apparatus may
be employed.
When it is required to collect and indicate only the vibrations of a sound of
determinate pitch, they should be collected as above explained, by means of a
resonator attuned to this sound, but if there is no necessity to distinguish a particular
sound amongst others of different pitch or nature, the use of a resonator is not indis-
pensable. Experience has shewn that by placing in the direction of origin of the
sound a microphone having sufficiently numerous points of contact, the vibrations of
the microphone produced by this sound, and transmitted to the telephonic receiver by
means of an electric current, are indicated by the manometric or sensitive flame with-
out recourse being had to the use of a resonator. The amplitude of these vibrations
is inversely proportional to the distance of the microphone from the source of the
sound, but other things being equal this amplitude and consequently the movement
of the manometric or sensitive flame are at their maximum when the microphone is
exactly turned in the direction of the source of the sound.
I will now describe in detail the microphonic and telephonic combination for the
reception and transmission of sound-waves and a galvanometric indicator for denoting
their intensity.
Referring to the drawings, figure 2 shews in plan, a diagram of an instrument in
which a single movable microphone is employed. Figure 3 is a similar view of the
same instrument with the addition of a telephonic receiver. Figure 4 is a diagram of
a multiple instrument in which several stationary microphones are employed. In
these figures, the same letters indicate the same parts.
In figures 2 and 3, a is the base or sound-board and 6 the carbon pencils of the
microphone capable of being rotated in azimuth upon an axis c on which it is mounted
by brackets d. The microphone is connected in circuit X with a battery e and galvano-
meter and in the case of figure 3, with a telephonic receiver g. Experience has
shewn that the effect of waves of sound upon the microphone is not only inversely
proportional to the distance of the source of sound, but also that this effect is less
powerful, according as the angle of incidence of the sound is more acute and attains
its maximum, when the sound strikes perpendicularly against the board a.

page_text: In order to determine whence a sound emanates, it is only necessary to rotate the
microphone in azimuth until the sound perceived in the telephonic receiver g or the
deflection of the galvanometer needle, attains its maximum.
If, for example, this maximum occurs when the microphone is turned to the
position a¹ it will be known that the direction of the sound is then normal to the
microphone.
Instead of a movable microphone, a number of fixed microphones facing towards
different points of the compass may be employed, as indicated, for example, in
figure 4 wherein four microphones a a² a³ a are represented as facing the four
cardinal points, the carbon pencils of each microphone being connected up in a
separate circuit (X¹X² X³ X¹) with a battery (e¹ e² e³ e) and galvanometer (ƒ¹ ƒ³ ƒ³ ƒ³)
as before.
With such an arrangement, if a sound received causes the needle of only one
of the galvanometers to be deflected it will be known that the direction in which
the sound arrives is perpendicular to the corresponding microphone. Thus, is
for example, the needle of the galvanometer f¹ only be deflected, the sound emanates
from the direction of the arrow W, but if two of the galvanometer needles be deflected,
it will be known that the sound strikes at a certain angle upon two out of the four micro-
phones, and that if the deflection of the two galvanometers is equal, the angle of
incidence of the sound upon the two microphones is also equal and therefore, emanates
from a source situated in the line bisecting the angle at which the two microphones
are placed relatively to each other. Thus, if for example, the galvanometers f³ f2
are deflected simultaneously and to the same extent, it will be known that the
sound emanates from the direction of the arrow S. W. which is in the line bisecting
the angle m, n, p.
If, on the other hand, the deflection of the galvanometer needles is unequal, it will
be known that the source of the sound is towards the one or other side of the
bisecting line, for instance, if the deflection off is greater than that of ', it will
be known that the sound emanates from a point situated between the directions S. W.
and S, and between the directions S. W. and W. if the deflection of the needle f¹
be the greater.
By employing a greater number of microphones, a much more precise determination
of the direction whence the sound emanates may be obtained, and to this end a
multiple instrument composed of say 8, 12, or 16, microphones arranged in the form
of a single polygon or of several superposed-polygons, may be employed.
It will also be understood that the arrangement of the apparatus may be modified
in practical details without varying the nature of the invention, for example the
circuits may comprise any number of galvanometers, if it is desired that the indica-
tions may be observed in different parts of the ship. Moreover, the deflections of
the galvanometer needles may be graphically registered by any suitable known
means, or the galvanometric indicator may be replaced by any equivalent recording
apparatus, furnishing graphic indications, such for example as the well known Siphon
Recorder.
Having now particularly described and ascertained the nature of the said inven-
.tion, and in what manner the same is to be performed, I declare that what I
claim is ;-
1st. An indicating apparatus denoting the direction of origin of an acoustic
signal, constituted by the combination of one or more resonators movable in
azimuth, with a manometric tube transmitting sonorous vibrations either to a
sphygmograph or a Koenig's manometric or sensitive flame in such manner that
the moment when the maximum effect produced by a sound wave is reached, this
maximum may be visually determined, as herein specified.
2nd. An apparatus for indicating the direction of origin of sounds, consisting of one
or more resonators acting upon microphones which transmit to, or reproduce in, a
telephonic receiver, corresponding sonorous vibrations in such way that the intensity

page_text: of the vibrations may he estimated orally or whereby the said vibrations may be
translated visually by causing the diaphragm of a telephone to act through a fluid
upon a suitable instrument such as a sphygmograph or a manometric or sensitive
flame, as specified.
3rd. An apparatus for indicating the direction of orign of a sound, consisting of
one or more fixed or movable microphones in circuit with a suitable receiving or
indicating instrument, such as a telephone, galvanometer, or Siphon Recorder,
whereby the amplitude of the vibrations of the microphone may be visually ascer-
tained or graphically recorded, as specified.
4th. The general combination and arrangement of the apparatus comprising reson-
ators and manometric or sensitive flame, as described and represented in. figure 1 of
the drawings for the purpose specified.
5th. The general combination and arrangement of the apparatus, comprising either
a movable microphone or a number of fixed microphones combined in circuit with
telephonic, galvanometric, or other receivers or recorders, as described with reference
to figures 2, 3, and 4, of the drawings for the purposes specified.
Doted this 21st day of October 1888
C. M. M. DE GOYON.
By A. M. & Win. Clark,
53, Chancery Lane, London,
Patent Agents.