US1986955A - Apparatus for bone audition - Google Patents

Description

Jan. 8, 1935. F. BEDELL.

APPARATUS FOR BONE AUDITIQN Filed Feb. 12. 1951 2 Sheets-Sheet l 'l NVENTOR Fmsom/cx B505 ATTORNEY FREQUENCY Jan. 8, 1935. BEDELL, 1;98 6,955

APPARATUS FOR BONE AUDITION Filed Feb. 12. 1951 2 Sheets-Sheet 2 Q Will? A HIHIH 5 |T1VE NTOR FREDER/C/f BEDfLL 1 ATTORNEY Patented Jan. 8, 1935 UNITED STATES PATENT OFFlCE 7 1,986,955 APPARATUS FOR. BONE AUDITION Frederick Bedell, Ithaca, N. Y. Application February 12, 1931, Serial No. 515,309 8 Claims. (01. 179-107) This invention relates to means for enabling the deaf to hear, and in particular to apparatus by which the sound vibrations are transmitted thru the bony structure of the head instead of thru the ear drum. The possibilities of bone audition have been recognized for some time, and various de vices have been constructed in the past which transmitted vibrations to the teeth or other bony structures, permitting the perception of sound by the deaf. The general objects of the present invention are to improve the quality, clarity, convenience, and sanitary characteristics of such apparatus, so as to make such apparatus practical and pleasing to the deaf.

In the transmission of sounds thru the bony structure of the head there is not such a wide range of tolerance as there is in vibrations thru the air, as bones lack the elasticity of the air; and I have found that the best results in individual cases cannot be obtained with the ordinary apparatus which lacks both concentrated hardness of vibration and selective quality. The type of vibration best adapted to bone audition is quite different from ordinary sound. Bone audition differs with different frequencies, and is improved for many people by giving greater intensity to the bone vibration as the frequency is increased, while for other people the reverse is true and audition 'is improved by giving the greater intensity as frequency is decreased. Furthermore, many individuals show a pronounced dip or minimum in their audition curves at a certain critical frequency, which I will refer to as the dip frequency,a term used in this sense by ear specialists. As the dip frequencies represent points of minimum audition, those particular frequencies should receive more emphasis than other frequencies. To meet these varying conditions and to give the bone the proper degrees of vibrations at different freling or weighting the frequency response as may be required. Accordingly, one general object of the present invention is to attain the maximum clarity in each individual case by regulating devices adjustable to the particular person.

Another object is to improve the quality by combining electrical amplification with mechanical de-amplification, or reduction of amplitude and increase of force, to give a hard type of vibration. Normal air audition is by the following path: outer ear, middle ear, to inner ear and then by auditory nerve to brain. In the middle ear are three bones called ossicles (the hammer, the anvil. and the stirrup) which by mechanical lever quencies, I provide means for selectively controlaction serve as a de-amplifier, converting vibrations of large amplitude and small force into vibrations of relatively small amplitude and large force. In like manner there is further de-amplification as the vibrations are transmitted from the middle ear to the inner ear (due to plunger action). Bone 5 audition detours around these internal physiological de-amplifiers, but for satisfactory audition this function must be performed. In my invention I have accordingly provided an external mechanical tie-amplifier to perform the function of the internal physiological de-amplifier, thus giving bone audition of character and natural quality not otherwise obtainable.

other objects are. to provide a sound proof. housing and mounting, to eliminate extraneous vibrations, and also to arrange so that the use of the apparatus will not disturb others. Further objects are to make the device convenient in use in any position, and arrange it so that the weight of the apparatus is not carried by the hand or teeth. Other objects are to make the apparatus more hygienic, to improve the applicators so as to make them adaptable to various angles and positions, and to permit one machine to serve several deaf people at the same time. In general the purpose is, by the combination of these and other features, to produce a practical and useful apparatus suiting the needs of the deaf and enabling them to listen to radio programs, phonographs, theaters, telephones, etc., without physical strain and with an improved quality of reception.

Referring now to the drawings,

Figure 1 is a general view, showing a microphone or other receiver, an electrical amplifier connected to the amplitude reducing mechanism or concentrator, which operates the applicator stick in the teeth of the listener.

Figure 2 is a cross-sectional view of the concentrator box, showing the amplitude reducing mechanism, frequency selector and amplitude control, and one form of hygienic applicator.

Figure 3 illustrates a modified form of amplitude reducing mechanism and also an alternative form of selective control.

Figure 4 shows a flexible applicator rod with detachable universal head.

Y Figure 5 shows another form of applicator head to apply to the cheek or other part of head.

Figure 6 illustrates the wooden splint type of applicator, a hygienic form which may be used and thrown away.

Figure 'I shows the tongue depressor type of hygienic applicator.

Figure 8 shows the multiple socket whereby several people may simultaneously use the same instrument.

Figure 9 shows an improved form of collapsible jointed applicator.

Figure 10 is an audition curve showing a typical dip at certain frequencies, and the manner of counteracting this minimum by selective frequencies.

Similar reference numerals refer to similar parts thruout the various views. w

A typical form of the apparatus is illustrated in Figure 1, which shows a microphone or telephone receiver 1 connected to the electrical amplifier 2 from which the amplified electrical vibrations. are transmitted to the fdeai speaker" or concentrator box 3. The vibrations which were electrically amplified at 2 are mechanically de-amplified in the box 3, that is the amplitude of vibrations undergoes a mechanical reduction or concentration, while the force of the vibration is correspondingly strengthened. The sound waves thus transformed into hard" mechanical vibrations of small amplitude are delivered to the stick or applicator 4 as longitudinal mechanical vibrations. When the applicator 4 is held between the teeth. or pressed against the cheek bone or other bony structure of the head, the vibrations are carried thru the bony structure to the inner ear where they are heard as sound. In order that a deaf person may adjust the osseous vibrations to his individual case, I have found it necessary to provide special regulating controls 6 and 7, by which both the amplitude may be controlled and the various selected frequencies may be modified or weighted according to the dip frequencies, to give the-bone the proper type of vibration to obtain the best bone audition, as will be described more in detail later.

In the form shown in Figure 1 a microphone is used as the initial receiver or pick-up for the sound waves, but it will be understood that it is merely illustrative, and that the apparatus may be attached to a telephone, phonograph pick-up, or radio, as will be obvious to those skilled in the art. In most radios, built for use with the ordinary loud speakers, sufiicient electrical amplification is obtained within the radio cabinet, so that the amplifier 2 would not appear as a separate unit but it would be there in principle. In Figure 1, in connection with the microphone 1, I have shown the usual rheostat 9 and source of electrical energy, conventionally shown as a battery 10, with the wires 11 leading from the microphone 1 to the amplifier 2, and the wires 12 connecting the output of the amplifier 2 (or radio set) to the input of the deaf speaker" or concentrator box 3.

The construction of electrical amplifiers being well known in the. radio and telephone art. it is unnecessary to describe the amplifier 2 in detail, except to make clear that an amplifier 2 is used in combination with the concentrator box 3 to produce the results desired.

Referring now to Figure 2, which shows the detail construction of a typical concentrator box 3. the amplified electrical oscillations come in thru the wires 12, and after being suitably modified by the regulating controls 6 and 7 (as will be describedmore in detail later), the electrical oscillations are delivered to the coil 15 located in the concentrator box 3. A balanced armature 16 is pivotally mounted to vibrate in the coil 15, and extends thru the coil 15 and the fields of the surrounding magnets 17 and 18 having the pole pieces 19, 20, 21 and 22 respectively.

Rubber cushions 23 are provided in the gaps between the said pole pieces 19, 20, 21, 22 and the vibrating armature 16, so as to limit the motion of the armature 16 and prevent its adhering to the pole pieces.

The vibrations resulting in the armature 16 when the coil 15 is energized are transmitted to a system of levers which have the function of reducing the amplitude and increasing the force of the vibrations. Any system of leverage may be used that is characterized by a reducing action, resulting in general from taking off the force at points nearer the fulcrum than the points at which the force is applied. One illustrative form involving a double reduction is shown in Figure 2, in which one end of the vibrating armature 16 is connected by the link 25 to the end 26 of the lever 27, whose fulcrum is at 28. At a point 29, nearer the fulcrum 28, another link 30 connects the lever 27 to the outer end of a second lever 31, whose fulcrum is located at 32. At an intermediate point 33 a rod 34 is pivotally attached to the lever 31, and on this drive rod 84 is threaded the nipple or socket 35 which delivers the vibrations to the rods or applicators used by the listeners. The vibrations finally delivered correspond to those of the rod 34 and socket 35. It will be seen that each lever 27 and 31 has served to reduce the amplitude and correspondingly increases the force of the vibrations of the armature 16. This gives a type of vibration adapted to be transmitted thru the bone of the user without disagreeable sensation, and results in an improved quality of tone.

Any other suitable form of reducing linkage or leverage may be used, and for example I have shown in Figure 3 a simpler form consisting of the link 25 connected to the outer end of a lever 40 which in this case is in the form of a fairly stiff spring clamped or fulcrumed at 41. The drive rod 34 is connected to the spring 40 at an intermediate point 42, so that the motion of the armature 16 is delivered to the drive rod 34 and applicator socket with reduced movement and increased force.

While in the foregoing I have shown a fixed coil 15 and movable armature 16, it will be understood that a moving coil could be substittued for the moving armature in a manner well known in the art, and in order to cover both types I prefer to use the phrase electromagnetic vibrating mechanism".

The armature, coils, magnets and leverages which have just been described are mounted in a non-magnetic frame 45 (see Figure 2) which is carried in a sound proof suspension inside of the outer box or housing 46. One form of sound proof suspension consists of connecting bolts 47, 47, provided with rubber bushings 48 which prevent the bolts from coming into direct contact with either the frame 45 or the housing 46. Thus any vibrations from the inner frame 45 must pass thru two rubber bushings before they can reach the 'outer housing 46. As a further precaution, the entire inner surface of the housing 46 is lined with sound absorbing material 50, and the opening in which the applicator socket 35 is located is lined with felt 51 or similar material. which serves to stop the transmission of audible sounds by air without preventing the vibratory action of the socket 35.

The housing 46 is preferably mounted in a bracket or frame 53 having trunnion bearings 54 and locking screws 55, so that the box 46 may be tilted to any convenient angle and then clamped in position. The bracket or frame 53 is also preferably mounted on a vertical pivot 56, which in combination with the bearings 54, gives a universal mounting permitting the box to swing freely to any position. 'Ihispermits the user to assume a comfortable attitude, with the weight of the apparatus carried by a suitable table or arm of a chair, and no weight carried by the user. The apparatus can thus be used without fatigue.

The function of the regulating controls 6 and '7 can best be understood by reference to Figure 10, which shows a typical audition curve A in solid lines, and a corresponding selective response curve B in broken line. The audition curve A represents a typical case, with audition shown as ordinates plotted against various frequencies. It will be noted that at a certain frequency there is a very pronounced dip or minimum in the curve, showing that there are certain frequencies to which the subject is particularly deaf. Such dip frequencies are 'fairly characteristic of many cases of deafness, though the particular frequency at which the dip occurs may be different in different individuals. It is therefore desirable that the vibrations from the apparatus be especially strengthened at frequencies corresponding to the dip frequencies of the individual. The function of the selective control is to provide highly artificial emphasis on certain frequencies wholly in relation to their degree of transmission thru the bone. and regardless of the estheti'c distortion which may result in the sound as might be heard by a normal ear. In general the means for accomplishing this consist of bi-pass or filter circuits, which by bipassing selected frequencies give relatively greater weight to others, or resonant circuits which accentuate selected frequencies, or by combinations of bi-pass and resonant circuits. After the various frequencies have been weighted to suit the individual case, thevolume of the combined wavesis brought up to the desired intensity by a volume control, which may be either of the series resistance or potentiometer type.

One preferred form is shown in connection with Figure 2. Across the wires 12, leading from the amplifier 2 or radio output, is connected a bi-pass system or filter circuit consisting of parallel bi-pass circuits, one having variable inductance 61 and the other variable capacity 62. A variable resistance 63 is generally provided in series with inductance 61, and a variable resistance 64 in series withcapacity 62, while a third variable resistance may be provided in series with both. Either bi-pass circuit may be used alone, but they are generally both used as will be described.

Using alone bi-pass circuit 62, 64, containing the capacity, this circuit will bi-pass high frequencies more and more as frequency increases, to an amount depending on capacity 62 and the series resistance 64, thus giving relatively greater weight to the low frequencies in the operation of the deaf speaker coil 15. On the other hand, using the inductive bi-pass circuit, 61, 63 alone, this circuit will bi-pass low frequencies more and more as frequency decreases, to an amount depending on inductance 61 and series resistance 63;

thus giving greater weight to the high frequencies in operating the coil 15.

When both bi-passes are used, the capacity and inductance are given values so that their product is equal to the square of the reciprocal of 211' times the dip frequency,

l 1 mm The cbmbined bi-pass circuit is thus antiresonant at the dip frequency, having a maximum impedance at that frequency, so that vibrations at dip frequency are passed on to the speaker coil. Vibrations at a higher or lower frequency are bi-passed, to an amount controlled by resistances 63, 64, 65 and the settings of 61 and 62. This bi-passing becomes less and less as the critical frequency is approached.

The apparatus is thus given a frequency response with a peak at dip frequency, determined by the proper values of the inductance and capacity as stated above. The response is gradually less and less as we go to higher and lower frequencies. The peak is most sharp when the resistances 63, 64, 65 are reduced to a minimum. Increasing resistance 65 reduces the amplitude of the peak. Increasing 63 and 64 broadens the peak, the relative values of 63 and 64 determining the relative steepness of the slope on the two sides of the peak. After the peak has been adjusted to effect the dip, so as to give a substantially uniform bone audition, the general intensity level or amplitude is then controlled by the variableseries resistances 66 and 67, either one or both of which may be used.

Another illustrative form of control, which, like the foregoing may be used with the concentrator box shown in Figure 1. Figure 2, Figure 3, or any other covered by this invention, is shown for example in connection with Figure 3, in which the general intensity level is controlled by a potentiometer circuit 68 instead of the series resistance 65, and means are provided for further accentuating the peak created by the bi-pass circuits described, this accentuating means consisting of a resonant circuit having a variable inductance 69 and variable capacity 69a in series, which can be adjusted to be resonant at the critical dip frequency.

The foregoing circuits are merely illustrative of the general principles. and the particular form of weighted frequency control is immaterial, so long as means are provided to insure that the vibrations delivered to the applicator are sufficiently accentuated in the frequencies corresponding to the dip frequency to permit the deaf person to smooth out the audition curve and then bring the intensity level to its best value. In this manner the maximum effect is obtained thru the osseous vibrations. whereas without proper weighting disagreeable notes and rattle may result from certain frequencies before others have produced their full effect; thus annoying reverberation peculiar to bone audition clue to the reflection of the sound vibrations in passing from the applicator to the teeth or bony structure is avoided. In the present invention this selective combination control is embodied directly in the apparatus where it can be adjusted by the deaf person to suit his individual characteristics. It is important that control be placed in his hands while he is receiving the osseous vibrations, as

the best adjustment varies not only with different individuals, but also to a certain extent according to the type of sound being received, vocal. instrumental, etc.

While in the foregoing description I have referred to the electrical amplifier 2 as coming before the frequency weighting control, one or more stages of amplification can be placed after such control if desired, without departing from the spirit of my invention, as will be obvious tothose skilled in the art.

Various forms of applicator rods 4 may be used to transmit the vibrations to the teeth or bones,

but for best results certain forms are preferable.

The improvements under the present invention are directed toward (1) combining a maximum of longitudinal rigidity with lateral flexibility, (2) universal adjustability (3) hygienic characteristics, and (4) use withmultiple sockets to make them suitable for groups or institutions.

Applicators have been used in the past consisting of rods, but these have had little'adjustability to various attitudes of the user, making them somewhat fatiguing. Collapsible or jointed applicators have also been proposed, but as these were provided with ordinary pintle joints, the transmission of longitudinal vibrations was impaired when bent or curved. In order to transmit longitudinal vibrations with a minimum of loss, screw or butt joints should be used, or preferably continuous elements rigid to longitudinal vibrations but flexible laterally. The applicators should be semi-flexible, by which I mean that while moderately flexible for continuous curvature, they cannot be given a sharp or discontinuous bend. v

A preferred form of applicator 4 is shown in Figure 4, consisting of a stranded or longitudinally laminated rod 70 provided with a universal applicator head 71. The base of the rod 72 screws into the concentrator box socket giving what corresponds to a butt joint to transmit the longitudinal vibrations. The body 70 of the rod is built up of a bundle of small rods or metallic filaments 73. A'single metal rod small enough in diameter to have the desired flexibility would have its sound carrying capacity reduced by the reduced cross-section, hence I use a bundle or cable to give greater sound conductivity. The group of conducting elements '73 is contained in a rubber casing 74. The upper ends of the rods terminate in the cap '75, into which is screwed the applicator head '71. This head "I1 is of the universal type, by which I mean that it is provided with a narrow neck 77 and rounded or spherical knob '16 so that the user may turn his head in various directions while still holding the applicator in his teeth, thus reducing fatigue. It will be understood that the rounded knob '76 need not necessarily be a perfect sphere, or spheroidal, but

that any generally. rounded form permitting a variety of positions may be used, as distinguished from a flat disk or plate which does not allow such free adjustment. The laminations in the preferred form of rod shown in Figure 4 and the rubber casing surrounding the rod, while in no way interferring with the normal transmission of sound vibrations of proper intensity, prevent by attenuation the excessive reverberation at times annoying in solid rods due to repeated reflections at the ends of the rod. This attenuation, due to friction between laminations and between the laminations and easing, becomes effective only when the vibrations or reverberations tend to assume undue intensity, being negligible in the transmission of normal sound vibrations.

The applicator heads are readily interchangeable for hygienic reasons or to use a different type of head. For example, in Figure 5 a fiat type of head 78 is shown which may be applied to the cheek or other bony part of the head, or may be placed against the ear, in which case it should preferably be provided with a nipple '79 on one side to fit the ear,-or be rounded as at '76.

In Figure 6 there is shown the simple splint type of applicator 80, usually made of a stick or rod of wood or other hard flexible material, such as used for surgical splints for example. Figure 7 shows a broad flat strip 81 of wood or other suitable material, similar to the tongue depressor strips used by physicians, which is readily engaged by the teeth. Both the splint and tongue depressor types of applicator are similar to articles already used in the medical arts as splints for broken bones and depressors for examining the throat, so that they are readily obtainable in hygienic sterilized form. These forms of applicators as contemplated in the present invention are intended to be used once and then thrown away.

Where several persons in the same household or in institutions desire to use the method of bone audition here described, the expense of a considerable number of individual boxes 3 may become prohibitive. To overcome this difiiculty I have provided a multiple socket 90 as shown for example in Figure 8, which has a threaded end '72 to screw in the socket 35 of the concentrator box 3. The body of the socket member 90 is provided with a number of applicator sockets 91, generally four in number, though more or less may be used. Each of these sockets 91 may be used for an individual applicator stick, so that several people may sit around the same instrument and receive the vibrations each thru his own applicator rod.

Where an individual wishes to carry his own applicator rod with him, it is desirable that it should be jointed or collapsible, so that it may be carried in the pocket or other small space. Where such applicators have used pin joints the loss in transmission has been considerable, especially when the joints were bent at a considerable angle in use.

I have found that the use of butt joints or screw joints, that is, joints rigid to longitudinal vibrations, considerably improves the efiiciency. Accordingly, I have shown in Figure 9 an improved form of jointed collapsible applicator rod made of sections 93 having screws 94 and sockets 95 at the ends so that they can be readily assembled into an applicator rod, or disassembled for carrymg.

Although the device herein described is primarily intended for application to some part of the head or ear for interpretation of sound by means of the auditory nerve, it is not limited to such application but may be applied to other parts of the human body, as to the fingers for tactual interpretation. It also may be applied to the ear drums stethoscopically like ordinary apparatus.

While in the foregoing I have described certain specific examples, it will be understood that they are merely for purposes of illustration to make clear the principles of the invention, which is not limited to the particular form shown, and is susceptible to various modifications and adaptations in diiTerent installations as will be apparent to those skilled in the art without departing from the scope of the invention asstated in the following claims.

I claim:

1. In an apparatus for bone audition, the combination of means for producing electrical vibrations corresponding to sound waves, electrical means for amplifying said electrical vibrations, a mechanical receiving element operated at large mechanical amplitude by the amplified electrical vibrations to produce mechanical vibrations corresponding to the extended amplitude, a reducing leverage mechanism operated bysaid mechanical element to reduce the amplitude and increase the force of the mechanical vibrations, and an applicator driven by said leverage mechanism with longitudinal vibrations, whereby concentrated vibrations may be delivered for bone audition.

2. In an apparatus for bone audition, the combination of a speaker box, a base, a' universal joint between said base and said box, and a. semiflexible applicator operated by said box.

3. In apparatus -for bone audition, a speaker box'comprising an outer casing, a sound absorbing lining for said casing, an iimer casing mounted within said outer casing on sound absorbing supports, an electromagnetic vibrating mechanism in said inner, casing, an applicator socket, and a de-amplifying lever mechanism between the electromagnetic vibrating mechanism and said socket, wherebysaid socket is driven with a concentrated hard quality of vibration.

4. In apparatus for bone audition, a semiflexible applicator rod comprising in combination a bundle of substantially'parallel elements bound together for transmitting longitudinal vibrations delivered longitudinally at the end thereof, means for holding said elements together, a connector head attached to one end of the transmitting elements, and an applicator head attached to the other end of said elements.

5. In apparatus for bone audition, an applicator head comprising in combination a reduced shank and a ball shaped head on said shank,

whereby the user may maintain contact while holding the applicator at various angles.

6. In apparatus for the deaf, the combination of a sound proof box, a universal mounting for said box, means for introducing amplified electrical vibrations corresponding to sound vibrations-into said box, means for converting said electrical vibrations into mechanical vibrations, a link operated by said last mentioned means, a lever operated by said link, mechanical means operated by said lever with a reduced motion, means for delivering the vibration so reduced to the user, and means operable by the user for varying the amplitude of the electrical vibrations and altering the relative weight of selected frequencies at will.

'7. In apparatus for bone audition, an applicator consisting of a rod-like member having longitudinal rigidity for the transmission of longitudinal vibrations and lateral flexibility in all directions, so as to readily adapt itself to various positions of the user, and'meansfor delivering vibrations to the rod-like member in a longitudinal direction, said rod-like member being sufllciently stifi to cause the longitudinal vibrations to predominate over the lateral vibrations.

8. In apparatus for bone audition, an applicator head, comprising, in combination, a reduced shank and a head on said shank of the universal type having a rounded curvature in various planes, whereby the user may maintain contact while holding the applicator at various angles.

FREDERICK IBEDELL.

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