US2451317A - Microphone adapted to be actuated by a bone structure of a user - Google Patents

Description

Oct. 12, 1948. w. R. BLAIR ET AL 1 2,451,317

MICROPHONE ADAPTED TO BE ACTUATED BY A BONE STRUCTURE OF A USER 3 Sheets-Sheet 1 Filed May 16, 1945 INVENTORS. WILLIAM R. BLAIR ALBERT E. WOODRUFF ATTORNEY Oct. 12, 1948. w BLAIR ET AL 2,451,317 MICROPHONE ADAPTED TO BE ACTUATED BY A BONE STRUCTURE OF A USER Filed May 16, 1945 3 Sheets-Sheet 2 FIGS F|G.7

INVENTORS. WILLIAM R.BLAIR ALBERT E. WOODRUFF akzazw ATTORNEY Oct. 12, 1948. w. R. BLAIR ET AL MICROPHONE ADAPTED TO BE ACTUATED BY A BONE STRUCTURE OF A USER 3 Sheets-Sheet 3 Filed May 16, 1945 INVENTORS. WILLIAM R. BLAIR ALBERT E. WOODRUFF ATTORNEY Patented Oct. 12, 1948 MICROPHONE ADAPTED TO BE ACTUATED. BY A BONE STRUCTURE OF A USER William R. Blair, Washingtoii, D. 0., and Albert E. Woodruff, Oak Park, Ill., assignors to Automatic Electric Laboratories, Inc, Chicago, 111., a corporation of Delaware Application May 16, 1945, Serial No. 594,058

9 Claims. 1

The present invention relates in general to microphones of the type employed for speech transmission and more particularly to microphones which engage the speakers body in such a way as to receive therefrom vibratory energy corresponding to the articulate sounds which issue from his lips.

Ordinarily, a microphone employed to reproduce speech is actuated by sound waves reaching it through the air. In very noisy locations, however, as on board aircraft or in the engine room of a ship, microphones of this type are not satisfactory, since the background noise which is picked up and transmitted along with the speakers voice is so loud that his words are rendered unintelligible. To remedy this situation, microphones designed to engage the speakers throat and to pick up only the vibrations of his larynx have been proposed. These are quite successful insofar as the elimination of background noise is concerned, but the pressure which they exert upon the throat makes them somewhat uncomfortable to wear; and, more important, the speech reproduced by them is of a somewhat guttural quality which is less, easily understood than normal speech.

It is the primary object of the invention, therefore, to provide a microphone which, like the throat microphone, does not pick up objectionable background noise and does not interfere with the speakers lips, but which reproduces speech of higher quality and greater intelligibility than the throat microphone. Another object is to provide a microphone suitable for use in noisy locations, which neither interferes with the speakers lips nor exerts any pressure upon his throat.

Tests disclose that the guttural quality of soundsreproduced by a throat microphone is duein a large measure to the fact that the human voice, as it exists in the region of the larynx, is imperfectly formed. Essentially an unfinished product, it subsequently is reinforced by certain resonating cavities of the head and modified by the tongue and lips, whereby in its finished form it contains overtones, or higher frequencies, not found in the region of the larynx. Contrasted with the predominately low frequency vibration of the speakers throat, the vibration imparted to certain bones of his head which adjoin the aforementioned resonating cavities now have been discovered to contain these higher audio frequencies in ample proportion and hence to be more truly characteristic of the sounds which issue from his lips.

One feature of the invention, therefore, is the, provision of a microphone which engages the speakers head in such a way that, during speech, it receives vibratory energy directly from a part of the bone structure thereof. Another feature is the provision of a microphone which engages the upper portion of the speakers nose and receives the vibratory energy from the nasal bone.

Other objects and features of the invention will become apparent from the ensuing description taken in conjunction with the drawings comprising Figs. 1 to- 13, inclusive.

Figs. 1 to 4, inclusive, illustrate one from of microphone according to the invention. More specifically, Fig. 1 is a side view of the microphone, part having been cut away to show the internal construction; Fig. 2 is a cross section taken along the line 2-2 of Fig. 1, the upper microphone cell being shown exploded; F g. 3 is a fragmentary view of one microphone cell showing in elevation the side thereof which engages the nose of the wearer; and Fig. 4 is a perspective view showing the manner in which the microphone is worn.

Fig. 5 is a schematic diagram of a circuit emplaying the microphone shown in Figs. 1 to 4.

Figs. 6 to 13, inclusive, illustrate an alternative form of microphone according to the invention. More specifically, Fig. 6 is a front view of the microphone; Fig. 7 is a rear view of the microphone; Fig. 8 is a bottom view of the microphone; Fig. 9 is a side view of the microphone, showing same applied to the face of the wearer; Fig. 10 is a view in elevation of one detail of the microphone; Fig. 11 is a view partly in section taken along the line I II I of Fig. 10; Fig. 12 is a diametral cross section of one microphone cell, greatly enlarged; and Fig. 13 is an exploded view of one microphone cell.

The microphone illustrated in Figs. 1 to 4, inclusive, comprises two identical microphone cells connected together by a U-shaped spring member I0. This member preferably is stamped from a flat sheet of resilient conductive material such as beryllium copper, after which it is bent into the shape shown. At its two ends, disposed op'-' posite one another, are a pair of dome-like projections I I each of which forms the rear electrode of one microphone cell.

The body of each cell comprises a light weight insulator I2 containing a cylindrical opening l3. This insulator, which may be molded of phenolic material, is cemented or otherwise suitably affixed to the member ID so that one of the electrodes I l projects into the opening I3 with the circular flange around that electrode covering one end of said opening; a shallow recess 14 shaped to receive member ID is provided in the insulator i2, insuring that said member and said insulator are assembled in the correct relationship to one another. The other end of opening 13 is covered by a flexible metallic membrane [5 which is held in place by a further insulator I6 cemented to insulator l2. metallic membrane is concavo-convex in shape and is so disposed that it protrudes through an opening i! in insulator i6. Itforms the front electrode of the microphone cell, and is provided with an elongated tail section I8 which extends beyond the supporting insulators to permit an electrical connection to be soldered thereto.

The opening 53, thus covered at both ends, forms an enclosed chamber adapted to be filled with granular carbon [9. It is desirable that the surfaces of the two electrodes which come into contact with the carbon (1. e., the convex surface of H and the concave surface of 15) be plated with gold or other chemically inert material having high electrical conductivity.

For the purpose of filling the carbon chamber, there is provided in the member It a small hole 20 havingunderneath it a passageway 2| through which the granular carbon may be poured into.

the associated chamber. When full, the mouth of the passageway may be sealed in any suitable way. Preferably, a thin sheet 22 of insulating material such as cellulose acetate is cemented to the entire back surface of the U-shaped member ID, thus covering hole 20 and at the same time partly insulating member a similar strip 23 of thin insulating material is cemented to the inside exposed surface of the member, its marginal edges being drawn down and cemented to outer ,margin of strip 22 in order to complete the insulation of member ID.

In order to insulate the two microphone cells froin the nose of the wearer the exposed surface of each front electrode i5 is covered by a thin cap of insulating material (not shown) shaped to conform withvthe convex face of that electrode and cemented thereto.

.7 Thus assembled, the unit is applied to the nose of the speaker as illustrated in Fig. 4. The two cells are positioned on opposite sides of the nose,

with the insulated metallic membrane [5 of each cell engaging the nose at a point directly over the nasal bone. Only a thin layer of skin covers this bone, and accordingly its vibrations are transmitted substantially without loss or diminution to the flexible membranes l5 of the respective cells. The consequent movement of each membrane, corresponding to the vibrationof the nasal bone, varies the resistance of the associated microphone cell thus to cause the current flowing through that cell to undulate in well known fashion. 7

It will be observed that the U-shaped spring to electrically connects the two cells in series as illustrated in Fig. 5, whereby a greater amplitude of output is obtained across the terminals it! with a given vibrational input to the cells. The spring also serves to press the two cells against the sides of the wearers nose in such a way as to make the unit virtually self supporting. Additional means may be employed to help maintain it in position, if desired; for example, a harness 25 may be used which extends around the head or, alternatively, fastens behind the ears like the bows of glasses. Wiring from the terminals! is carried by this harness up be- As shown in the drawings, the

4 tween the eyes and over the forehead to a point at the side or the rear of the head where it then may connect to the external circuit without interfering with the wearers vision or comfort.

The position of the nasal microphone may be varied somewhat to suit the individual wearer. Since the nasal bone underlies approximately the upper half of his nose, the cells may be positioned rather high on the nose, as shown in Fig. 4, or may be situated somewhat lower than indicated. It will be understood that the pressure of the unit is born by the bone structure of the nose in either case, so that breathing is nowise impaired Neither does the unit obstruct the wearers vision, due to its small size. As a matter of fact, it may easily be made an integral part of eye glasses or goggles, if such are to be worn by the speaker. Laboratory tests prove that the speech reproduced by the nasal microphone is of high quality, containing the overtones or higher frequencies in such proportion as to make for easy understandability. It picks up no sound vibrations except those impressed upon it by the speakers nasal bone structure, andhence maybe employed even in very noisy locations withoutany danger whatever of rendering the transmitted message unintelligible. E'xceedingly light in weight, it is as comfortable to wear as ordinary glasses; it does not obstruct breathing either through nose or mouth, and does not interfere in any way with normal muscular movements of the mouth, face, or throat.

Consideration now will be given to an alternative form of construction, reference being had to the transmitter illustrated in Figs. 6 to 13, inclusive. As in the preceding case, the unit comprises a pair of microphone cells positioned on' opposite sides of the bridge of the nose, and it will be most convenient, to begin by describing the construction of one of these cells. They are of the inertia type; wherein the housing, under the influenceof sound waves conducted to the cell by the bone structure of the speakers' nose, vibrates with respect to an internally suspended electrode, the latter remaining stationary due to its own inertia,

Referring to Figs. 12 and 13, it will be seen that the housing comprises an insulating shell molded of phenolic material. Resting upon a shoulder 3| near the bottom of this shellis a paper ring 32, and upon the ring rests a thin metallic disc 33. A rather heavy generally peara shaped electrode 34 is' riveted or otherwise suitably aflixed to the center of the disc, the outer margin of the disc being clamped tightly against the shoulder 3! by the rim of an'invertedcupshaped member 35, which is screwed into threads provided for that purpose on the interior of shell 30. The flexibility of disc 33 (which is utilized to the fullest extent by makingelectrode 34 small at the bottom, thus to leave the major portion of the disc free to move) permits movement of electrode 3 3 and shell as relative to one another.

Within the chamber 36 formed by member and disc 33, and juxtaposed to the electrode 34 carried by the disc, is a further electrode 31 which is held in place by a hollow screw stud 38 eXtend-.

ing through a hole 39 in the base of the cupshaped member. Electrode 31 and stud 38 are in-l sulated from member 35 by paper washers 40 and 4!.

, When the cell has been thus assembled, granular carbonis introduced into the chamber 36' through the hollow stem of stud 38, after which this passageway is closed by screw 42. The surfaces of electrodes 34 and 31' which come into contact with the carbon granules should be plated with gold or other chemically inert metal having high electrical conductivity. The interior of the cup-shaped member 35, on the other hand, is insulated from the carbon, for example with bakelitevar'nish.

It will be observed that the screw stud 38 forms one terminal of the microphone cell, while the cup-shaped member 35, being connected to electrode 34 through the medium of disc 33, forms the other. To facilitate making electrical connection with the latter, a spring clip 43 is provided which is adapted to be slipped into the insulating shell in such a way as to grip the exterior wall of member 35, the terminal end of the clip extending radially outward through a slot 44 in shell 30.

The way in which the microphone cells are supported now will be described with reference to Figs. 6 to 11. A mounting plate 45, the upper portion of which is bent to conform with the slope and curvature of the wearers forehead, is applied to the forehead at a point directly above his nose, a loop 46 and a strap t! being provided to hold it in place. This strap extends around the wearers head like a hat band and may be supported in turn by other straps passing over the top of his head. Preferably both faces of the upper (head engaging) ortion of the plate will be covered by a thin sheet of cellulose acetate, not shown, for purposes of insulation.

A narrowed stem portion extends downwardly from the Wearers forehead to a point adjacent the bridge of his nose, terminating in four laterally extending lugs which are bent over at right angles to the stem of the mounting plate; these lugs carry a pair of pivot pins 48 and cooperate with a pair of arms 49 to form hinges pivotally supporting said arms. A spiral tension spring 50, enclosed in a flexible rubber tube 5|, interconnects the two arms, tending to draw them together. Each end of the spring is soldered to a metallic insert 52 molded into one of the arms, as best seen in Figs. 10 and 11.

Also soldered to each insert is a socket 53 for re'ceivingthe ball-shaped end of the stud 38 of one microphone cell. The ball and socket swivel thus formed permits considerable angular adjustment of the microphone cell with respect to its associated supporting arm, thus to adjust the cell to the nose of the wearer. Preferably the swivel will be made tight enough to prevent unintended dislocation of the cell after it has been adjusted.

A circular flange 54 on each arm 49 limits the extent of movement of the associated microphone cell and also sufiiciently covers the rear of the cell to prevent accidental contact therewith.

Making the socket 53 grip the ball rather tightly has the additional advantage of insuring good electrical contact between the two. The importance of this will be appreciated if it is noted that the two microphone cells are designed to operate in series, the electrical circuit between them being completed over spring and the insert 52 and socket 53 of each arm. A pair of wires 55 connected to the terminal clips 43 extend via a pocket in the supporting strap 41 to a point near the back of the wearers head, where they connect to the external circuit. (This circuit, it will be understood, is similar to the externa1 circuit of the microphone unit shown in Fig. 5.) A clip 56 is provided on the mounting plate 45 to hold the wires 55 in such a position that they cannot interfere with the wearers vision.

In operation, the vibrations of the nasal bone structure of the wearer will vibrate the entire casing of each microphone cell when he speaks. Due to its inertia, electrode 34 tends to remain fixed in space (i. e., stationary), resulting in a relative movement between electrode 34 and elec-- trode 31, with a consequent change in circuit resistance as is well known in the art.

Having fully described the invention, what we consider new and desire to protect by Letters Patent will be set forth in the appended claims.

What is claimed is:

1. In a device for the transmission of speech, a microphone, means for supporting said microphone against a sound conducting bone structure of the speaker so that said bone structure imparts vibratory energy to said microphone; said supporting means including a ball and socket joint permitting adjustment of the position of said microphone relative to said'bone structure and an electrical circuit extending to said microphone over said ball and socket joint.

2. In a device for the transmission of speech; a pair of microphone cells; means supporting said cells on opposite sides of the speakers nose so that the bone structure of his nose imparts vibratory energy to said cells; said supporting means including a structure affixed to the speakers head, and aball and socket joint for each cell movably supporting that cell upon said structure, whereby the angular position of each cell with respect to the speakers nose is adjustable.

3. In a device for the transmission of speech; a pair of microphone cells; means supporting said cells on opposite sides of the speakers nose so that the bone structure of his nose imparts vibratory energy to said cells; said supporting means including a structure afiixed to the speakers head, and a ball and socket joint for each cell movably supporting that cell upon said structure, whereby the angular position of each cell with respect to the speakers nose is adjustable; and an electrical connection betweensaid two cells extending over both of said joints in series.

l. In a device for the transmission of speech; a pair of microphone cells; means supporting said cells on opposite sides of the speakers nose so that the bone structure of his nose imparts vibra-- tory energy to said cells; said supporting means including a base member afiixed to the speakers head, two auxiliary members movably mounted upon said base member, said members corresponding respectively to said microphone cells, a joint for each microphone cell pivotally supporting that cell upon its corresponding auxiliary member, whereby the angular position of that cell with respect to the speakers nose is adjustable, and spring means acting upon said auxiliary members so as to urge said cells toward the speakers nose.

5. In a microphone, a pair of insulators each having an opening extending therethrough from side to side, means whereby one end of the opening through each insulator is covered by a thin metallic diaphragm individual to that particular insulator, said diaphragm being movable in accordance with audio frequency vibrations of a body engaging such diaphragm, means whereby the other end of the opening through each insulator is covered by part of a unitary metallic member common to both insulators, and microphonic material in the opening in each insulator for completing an electrical circuit between said ings with its concave side toward said other opening, said member comprising a movable electrode which is adapted to engage a bone structure of the body of the speaker and which is responsive to audio frequency vibration of said body, and granulated carbon in said opening for completing an electrical circuit between said two,

electrodes.

7. In a microphone cell, an insulator having a circular opening extending therethrough from side to side, a stationary electrode cemented to said insulator so that it covers one end of said opening, said electrode having a dome-shaped portion which protrudes into said opening, a thin-Walled concavo-convex member cemented to said insulator so that it covers the other end of said opening with its concave side toward said opening, said member comprising a movable electrode the convex side of which is adapted to directly engage the bone structure of the speaker's body and responsive to audio frequency vibration of said body, microphonic material, and means whereby said material is interposed in said opening between said two electrodes after said electrodes have been cemented to said insulator.

8. ma device for the transmission of speech, a pair of microphones each having an insulator, each said insulator having an opening extending therethrough from side to side, means whereby one end of said opening through each said insulator is covered by-a thin metallic diaphragm individual to that particular insulator, means,

whereby the other end of said opening through each said insulator is covered by part of a metallic spring member common to both said insulators, microphonic material in said'opening in each said insulator for'completing an electrical circuit between said spring member and said diaphragm individual to that insulator, said spring member adapted for urging said microphones towards each other thereby to cause said diaphragms to press against opposite sides of the nose of a, user of said device, said diaphragms actuated by vibrations of the users nasal bone responsive to speech by said user.

9. In a device for the transmission of speech, a pair of microphonecells each having an insulator, each said insulator having a passage extending therethrough with an opening on each side, a stationary electrode affixed to each said insulator so that said electrode covers one of said openings in that particular insulator, said electrodes having dome-shaped portions extending into the respective said one openings, a thin-. walled concavo-convex element afiixed to each said insulator so that said element covers the other of said openings in that particular insulator with its concave side toward said other opening, each said element comprising a movable electrode, microphonic'material in said opening in each said insulator for completing. an

electrical connection between said two electrodes in that particular insulator, a spring member common to both said insulators and adapted for urging said pair of microphone cells towards each other,-thereby to cause said movable electrodes to directly engage a bone structure of the body of a user of said device, said movable elecrades actuated responsive to audio-frequency vibrations of said body.

WM. R. BLAIR.

ALBERT E. WOODRUFF.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Great Britain Nov. 1, 1928

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