US2755336A - Electrical stethoscope - Google Patents

Description

July 17, 1956 F. B. zENER ETAL ELECTRICAL STETHOSCOPE Filed Jan. 7, 1955` l rraeA/EV.

United States Patent() ELECTRICAL STETHOSCOPE Francis B. Zener, Santa Barbara, and John A. Moseley, Malibu, Calif.

Application January 7, 19.55, Serial No. 480,370

4 Claims. (Cl. 179-1) This invention relates generally to a novel electrical stethoscope and particularly describes such a device including a new and unusually effective microphone housing for use with a stethoscope.

In the preferred embodiment of the present invention there is provided a microphone housed in a body, the output of the microphone being arranged to be amplified by conventional electrical amplifier means. The output of the amplifier, in the form of an amplified electrical signal, is fed to a small speaker whose acoustic output is connected to a pair of flexibly mounted tubes terminating in conventional plugs for insertion into the ears of the user.

Although electrical stethoscopes have been proposed in the past, they have been subject to disadvantages in operation and use principally resulting from the picking up and amplifying of unwanted sounds. Such sounds are caused, for example, by the microphone or microphone housing rubbing against the clothing or body of a person being examined. By the present construction these disadvantages are minimized and virtually eliminated. Preferably a microphone with a frequency response of from 40 to 6000 cycles per second is employed in the invention and since extraneous sounds are excluded as above mentioned, the present invention is particularly well suited for detecting respiratory, cardiac and peristaltic sounds as well as the fetal heartbeat.

Accordingly it is a principal object of the present invention to disclose a novel electrical stethoscope.

Another object of the invention is to provide an electrical stethoscope whose construction minimizes the introduction of unwanted extraneous sounds into the system.

A further object is to disclose, in the above apparatus, a microphone housing consisting of a body having a hollow chamber near one end thereof for resiliently housing a microphone and including in its other end an impedance-matching section including outwardly flared horn communicating with the microphone chamber through an aperture formed in the housing.

A further object of the invention is to disclose an apparatus of the above character including means for protecting the microphone from damage caused by jarring when inadvertently dropped or otherwise mishandled, as well as to acoustically shield the diaphragm of the microphone.

These and other and allied objects of the invention will become clear from a study of the following description of a preferred embodiment thereof taken in connection with the accompanying drawing in which:

Fig. 1 is a diagrammatic layout of a complete elec trical stethoscope embodying the present invention.

Fig. 2 is a longitudinal sectional view through the microphone housing; and

Fig. 3 is a fragmentary sectional view, on an enlarged scale, taken on line III-III of Fig. 2.

Referring now in detail to the drawing there is shown in Fig. l a microphone housing indicated generally at 2,755,336 Patented July 17, 1956 ice connected through a suitable electrical cable 12 to the input of an electrical amplifier indicated generally at 14 supplied with electric power through leads 15. The amplifier 14 may desirably include conventional volume control means 16 and its output is fed through electrical cable 18 to the female portion 20 of a detachable plug jack connection of conventional design.

A small dynamic speaker 22 is provided with an insertable plug 24 removably receivable in known fashion in the jack 20. The acoustic output of the dynamic speaker or transducer 22 is coupled through a resilient sleeve 26 to the yoke portion 28 of a stethoscope. Acoustic waves originated by the transducer 22 and fed to yoke 28 are further conducted through resilient sleeve members 3f) to ear tubes 32 terminating in inwardly directed earpieces 34. The apparatus just described includes resilient member 36 to hold the component members in position as indicated and consitutes the well known physicians headpiece or harness for listening to sounds such as heart beats andthe like.

A preferred form of the microphone housing 10 used in the present invention is shown in detail in Fig. 2. As there appears, the housing body 10 is made of rigid material having in its rear portion a hollow chamber indicated generally at 4f), and in its front portion an impedancematching section including an outwardly flared horn indicated generally at 42. Within the chamber 40 there is provided a microphone indicated generally at 44. The microphone 44 is preferably of the piezo-electric type, affording good frequency response from the relatively low frequency heart beat sounds to the respiratory and peristaltic sounds of higher frequency.

The chamber 40 is desirably cylindrical in shape and a layer of resilient acoustic insulation material is provided as a lining for both the cylindrical side wall of the chamber 40 as well as the major portions of the end walls defining the chamber. Thus the resilient lining includes a cylindrical portion 46 extending the length of the chamber dii, a disk-shaped portion 48 across the rear end of the chamber and an annular portion 50 across the front end of the chamber. The resilient members 46, 48 and 5f) may be made of rubber or suitable substitute having similar resilient characteristics.

The microphone 44 within the chamber 40 is supported on the cylindrical resilient member 46 and is provided with output leads 56 and 58, the former lead being grounded at 60 to an access and mounting plate 62 coustituting the rear closure member for the microphone chamber and held in position relative to the body housing by suitable fastening means 64. The end plate 62 includes an aperture 66 therethrough and a conventional coupling member 68 is threaded therein and held in assembled relation as by nut 70. The outer portion of the coupling member 63 includes a portion of increased diameter 170 to which may be threadedly connected the female portion of a conventional electrical fitting 72. Electrical connection is thus made between the contacts at 74 and the conductor 5S is thereby connected to the output lead 76 which is desirably a portion of coaxial cable 12 as indicated.

In the front portion of the housing body 10 the impedance-matching section 42 includes outwardly and frontwardly diverging walls 80 which are convexly formed in an exponential curve of revolution. At the inner end of the curved walls 80 the horn 42 communicates with a restricted throat or channel 82 which terminates rearwardly in an aperture 84. Thus the housing body 10 is provided, in effect, with a. transverse partition dividing the microphone housing 40 in the rear portion of the body from the horn 42 in the front end thereof, and this partition is provided with the central aperture 84. Desirably the rear surface of the partition, constituting front wall of the microphone housing chamber 40 includes a recessed portion 86 constituting an enlarged air chamber immediately rearwardly of and in communication with the aperture 84. The microphone 44 includes a frontwardly disposed llexible diaphragm 88 which is thus exposed to sound waves existing within the air chamber 86.

It will now be understood that the front end of the horn 42 formed in the housing body 10 and dened by the circular rim 90, may be placed in direct contact with a portion of a persons body near the origin of sounds to be investigated by means of the present apparatus. The rim 90 effectively isolates the microphones diaphragm 88 from sound waves originating elsewhere than the particular area surrounded by the rim 90. The sound waves thereby transmitted into the horn 42 are conducted through the throat portion 82 and the aperture 84 into the air chamber 86. When the horn 42 is constructed as herein shown and described, body sounds are thus transmitted into the air chamber 86 and impinge on the diaphragm 88 with a minimum of attenuation, and the resilient mounting of the microphone within the rear portion of the housing body etectively isolates the microphone from extraneous sounds or vibrations.

Accordingly' it will be seen that we have provided a novel and useful device by which to receive and make audible various body sounds for diagnostic purposes. Moditications and changes from the specific forms of the invention hereinabove shown and described as illustrative may be made without departing from the spirit of the invention, and such modifications and changes are intended to be embraced within the scope of the appended claims.

We claim:

l. An electrical stethoscope comprising: a microphone housing including a generally tubular body having a front portion provided with an outwardly directed horn converging inwardly to an axial channel and an enlarged air chamber formed in the body rearwardly of the channel and in communication therewith and a rear portion provided with a cylindrical microphone chamber; a layer of resilient, soundinsulating material lining said microphone chamber; a microphone within the microphone chamber supported by said layer having a diaphragm exposed to said air chamber; electrical conductors operatively connected to the microphone and leading outwardly of the housing; amplifier means connected to said conductors for amplifying signals from said microphone and provided with output terminals; an elongated electrical cable connected to said output terminals; an electroacoustic transducer operatively connected to the other end of said cable; a pair of flexible tubes connected to said transducer terminating in laterally spaced ear members; and harness means for resiliently biasing the ear members toward one another.

2. The invention as stated in claim 1 wherein the walls of said horn are convexly formed in an exponential curve of revolution.

3. In an electrical stethoscope, a microphone housing comprising: a body of rigid material having an enlarged cylindrical chamber in its rear portion; a layer of resilient material lining the side wall of said chamber; a closure means forming an outer rear end wall for said chamber and provided with means for leading an electrical conductor therethrough; a transverse partition intermediate the ends of said body forming the front inner end wall of said chamber and provided with a central aperture therethrough, said front inner end wall having a frusto-conical surface inclined steeply outwardly from said aperture; and an acoustic impedance-matching section formed in the front portion of the body and terminating inwardly in communication with said aperture.

4. In an electrical stethoscope: a housing made of rigid materiai and having front and rear portions, the rear portion being provided with a microphone chamber formed therein and the front portion including a transverse partition having a small centrally disposed aperture formed therein, the partition having a rearwardly directed frusto-conical surface inclined steeply outwardly from the partition aperture and a front surface constituting an acoustic horn flaring outwardly from the aperture; and a microphone disposed within the chamber including a diaphragm facing said frustoconical surface.

References Cited in the file of this patent UNITED STATES PATENTS 1,540,585 Abbott June 2, 1925 1,791,932 Miller Feb. l0, 1931 2,145,449 Lockhart Ian. 31, 1939 2,419,471 Thibos Apr. 22, 1947

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