Improvements in or relating to Apparatus for Rendering Audible Slight Sounds.
Year: 1899

page_text: Date of Application, 7th July, 1899-Accepted, 26th Aug., 1899
Improvements in or relating to Apparatus for Rendering Audible
Slight Sounds.
A communication from MARTIN WALLACH NACHFOLGER, of 'Cassel, Prusein.
I, ALFRED JULIUS BOULT, of 111, Hatton Garden, in the County of London,
Chartered Patent Agent, 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:
The present invention refers to an apparatus by means of which all kinds of
sounds high as well as low-can be rendered of equal intensity in membrane-
hearing-apparatus, such as phonendoscopes, or, when required, one sound or
another out of a greater number of simultaneous sounds may be rendered more
audible than others.
In the membrane or diaphragm hearing devices used up to the present time,
it has been observed that when several sounds are simultaneously heard, the
lower sounds are more distinctly audible than the higher ones, which evidently
points to an imperfection in the hearing or transmitting device. This drawback
of the apparatus, protected by German Patent No. 85784, has become evident
in several cases of auscultation of pathological character, in which certain sounds,
which were produced simultaneously with others, could not be heard with sufficient
distinctness.
To overcome this drawback it has proved to be advantageous to provide a
passage between the hollow chamber or recess e and the outer air, the width
or opening of which may be regulated according to requirements or it may be
reduced to zero, by closing it altogetlier. The principle of this sound solector
33
is based on the fact that the portion of sound which passes through the passage
outwardly, and which is proportional in all sounds to the area of said passage,
is proportional in the separate sounds to the duration of the oscillations, i.c.
lower sounds will lose more of their intensity when the passage is open than
higher sounds, which are caused by the more rapid oscillations. Owing to this
arrangement the higher sounds can be transmitted to the ear with greater
intensity.
The invention is carried out in the construction shown in the accompanying.
drawing. From the air chamber e a passage is bored or formed through the
disc body S of the instrument, where a plate w (Figure 2) pivotted on a pin 5,
is so arranged, that its opening (, can be made to coincide partly, or wholly, or
not at all, with the said passage z whereby the passage z can communicate partly
or wholly with the atmosphere, or be entirely closed against it. Such, or a
slide, or a similarly acting device may be arranged also in both of the ear tubes;
when the car-tubes issue from a common connecting tube, one valve is preferably
arranged in the latter.
For the purpose of rendering high sounds especially clear a
transmitter is
provided for the transmission of the sound from the outer diaphragm p to the
inner membrane or diaphragm m. The purpose of this transmitter æ, made of

page_text: hardened indiarubber or the like, is to render the contact between the two
membranes perfect, even when the pressure on the outer membrane, or on the
small rod connected to it, is not sufficiently strong to produce an intimate contact
between them. For, when such pressure is excessive, the slight oscillations of
the inner membrane, and consequently the sensitiveness of the instrument are
interfered with and affected.
The object of the invention is to render the transmission of sound as clear
and free of undesirable or secondary noises as possible.
To attain this result it has been found advantageous to employ a spring y of
special shape (Figures 3 and 4) made say of German silver, which cannot be
moved from one side to the other in the recess e, and which does not possess any
individual sound of its own. This spring y is star- or cross-shaped, the middle
portion of which permits the passage of air to the passage z; the spring is so
arched that it fits into the hollow space .e, while its arms, with the slight pro-
jections towards or at the ends are in contact with the membrane m.
It has also been found of advantage to have the edge S' of the disc S slightly
chamfered towards the outside (Figure 1) in such a manner that on screwing
on the clamping ring which is also slightly chamfered, the membrane mis
forced to arch slightly outwardly owing to the pressing down of its edge.
Having now particularly described and ascertained the nature of this said
invention, as communicated to me by my foreign correspondent, and in what
manner the same is to be performed, I declare that what I claim is:-
1. In apparatus for rendering audible slight sounds of the kind described, a
connecting passage between the air chamber below the membrane, and the outer
atmosphere, and means for closing said passage wholly or partially so as to
regulate the intensity of the different sounds according to requirements.
2. A construction of apparatus of the kind described in which the disc body
is provided with a passage and with a pivotted plate with a hole in it capable
of registering witli said passage substantially as described.
3. A construction of apparatus of the kind described in which passages and
covering plates or valves are arranged in the ear tubes, or a single covering plate
or valve is arranged in a tube from which both the ear tubes issue, substantially
as described.
4. A device as specified in Claims 1 and 2 in combination with a disc body
for the purpose of transmitting the oscillations from the outer diaphragm to the
inner diaphragm and to effect an intimate contact between the two diaphragms,
while avoiding the disadvantages which would result from producing a contact
between the two diaphragms, by pressure on the outer membrane, substantially
as described.
5. A device of the kind described in combination with a star shaped spring
of sheet metal and a chamfered edged disc body and clamping ring for the purpose
of causing the membrane to arch outwardly, substantially as described.
6. The complete apparatus for use in rendering slight sound audible sub-
stantially as described or illustrated in the accompanying drawings.
Dated this 7th day of July 1800