US 1678564 A
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July 24, 1928; 1,678,564
B. E. ELDRED METHOD FOR AIDING AUDITION Filed Dec. 10, 1924 l l dl e Gexjezwfbr v II .2 z
MM: Earner-afar l Patented July 24, 1928 UNITE-D -sT'ATE IS 'IHPAT-YEINT OFFICE.
BYRON ELDRED, or msme'ron, mew Yonx.
METHOD FOR AIDING AUDITION.
Application as December 10,1924. Serial no 755,077.
My invention consists in 'a' method and apparatus for aiding the audition of persons of defective hearing.
The method consists in producing and.
emitting into the surrounding space a continuous and sustained succession of rythmical air Waves of suiiicient pitch and-amplitude whereby the ears of persons, of defective hearing are rendered more sensitive to normal sounds. S uch waves are hereinafter referred toas sensitizing waves.
y method is useful not only in enabling more or less deaf persons to intelligibly hear sounds or speech of normal intensity while, they are within the influence oi such waves,
but also for improving the audition of somev repeated'subjecclasses of deaf persons, b tion to the influence such sensitizing waves. w While ll find that in most cases of defective audition the. sensitizing. wave-may be applied to the best advanta e at a certa n pitch and amplitudeto suit t e special case of deafness, and this pitch and amplitude may be readilydeterinihed by experiment for an individual case, i also find that greatly improved hearing results in most cases by waves of inaudible frequencies and substantial magnitude. Such waves 'I propose for general use in theatres, churches, auditoriums, homes and the like, .tinditwill be obvious tea-person skilled in the art that the amplitude of the wave so employed should he adjusted to suit the dimensions and general interior design of the auditorium.
In improving the acoustic properties of auditoriums, theatres, churches andthe like for the reception of sound by persons of dc fective hearing, I find that sensitizing waves in irequenc' and amplitude predetermined for a suitab e sensitizing effect. for average persons of defective hearing are effective. These waves have a healthy natural efiect upon the abnormalear which is probablybrouight about by efiectinga responsiveness o the tensor tympani muscle; 'lhis tensing efiect upon the relaxed vibratory system of the deal ear is practically entirely without efiect upon the normal healthy ear. I do not, however, wish to limit myself to the use of inaudible frequencies in the car-- rying out of my invention as certain audilole frequencies, especially those approaching the limits of audibility, will he found to be quite satisfactory-hut waves of low roughly placed between and 5000 double vibrations per second, although the authorities diflt'er widely as tothese limits.
I find that it is desirable to use a wave which has little or no tonalquality for the or no auditory nerve response and for that reason may be ap lied with the desired strength or amplitu e without causing nerve humanear because such a wave efiects little fatigue, or car discomfort, especially to per-- 1 sons of normal hearing.
In thepractice of my invention, the adustment of amplitude is apparently more important than the adjustment of frequenciesxof vibration. I find that too great an amplitude may operate to defeat the purposes of the invention and that deaf persons within the influence of sensitizing waves of too great amplitude may not hear, and may experience uncomfortable sensations.
. In soine special cases, particularly in, chiltions of'highfrequency.
In, either case, the essential condition is that there is produced a forceful action by the air waves on the mechanism of the ear. WVith wavesot low frequency, the amplitude of the waves isv made sufiicient to adequately afl'ect the ear mechanism, while with waves of high frequency the effect of the very rapdren, it will'be found necessary to use vibra- 4 idly repeated applicationof the smaller am pliti1de waves exerts such force on the ear mechanism as to produce the desired eiiect. Thereis no practical diiiicnlty in properly adjusting the amplitude of the waves, since thewave-producing mechanism may be adjusted to the proper degree, or the listener may vary his distance from the wave-producing apparatus.
It is well known that deaf people who can he made to hear at all require-sound waves of excessive amplitude (i. every loud tildtalking) to overcome their defective audition.- I have found that sensitizing waves oi sub-audible or super-audible frequencies serve the same purpose as supplying exces-' sive amplitude. to the sound waves of the soundcommunication to be imparted. And the-relief efiected by my invention is thus two-fold in that in voice communication it saves the efi'ort of very'loudtalking by the person who is endeavoring to communicate with the person of defectiveaudition.
The sensitizing waves used in thisman ner while referably of pure form, need not be so free rom what may be termed staccato components. nor of as great am litude as when amore lasting efiect on the caring is to be reduced- In this latter'j case the waves s ould. be of substantially pure form, that is containing a dominant percentage of afundamental note not compounded with waves of difierent frequencies. a
I do not wish to be limited. to any special" type of apparatus or device for carrying out my invention. I have shown and described diagrammatically two types .of apparatus which I have found suitable: Fig. 1' shows an apparatus for the generation of low frequency sensitizing'wav'es; Fig. 2 shows an apparatus forthe generation of high frequenc sensitizin waves Re erring to Fig. 1 M is a motor having a rheostat. R in its field circuit to control the speed of the motor. 'N is a self-excited alternatin current generator having a commutator 1 from;which direct current is delivered to the field magnet coils N and through wires 20, 21 to the coil L surround ing one limb T of the magnet I. Collector rings N, on, the generator shaft deliver alternating current through wires 22, 23, to coil L this circuit including a, resistance R The coil L consists of onl a few turns, is light in weight and woun around'the tubular end of a cone shaped diaphragm D of light fibrous material, such as paper or archment, which is carried by a thin rub- .er ring F secured to the edge of a circular opening in the bafile plate B. The diaphragm is thus free to move in the direction of its axis. The coil L is located in the magnetic field between the poles 1,, I of the magnet I, the end of the core I, extending into the coil L Due to theoscillations of I the alternatin current, a magnetic field will tion wit be set u in 3 which will change its direceach change in direction of the oscillating current. When this magnetic field is in the same direction as that due to magnetl, the two fields will act to at tract each other, thereby causing coil L to .move along its axis from; its normal position-. When the magnetic field of L reverses its direction a repelling action will take place and the coil L will move in the other direction. In this manner the diavrected. The frequency of the waves may be controlled by rheostat R andthe amplitude may be varied by rheostat R For producing high frequency air waves, I may use the device shown in Fig. 2.. The
wave generator is of the same construction as that 'desc'ribedin Fig. 1, the unidirectional and oscillating currents delivered to the coils. L and iL, being furnished however from an alternating current rectifier" and an oscillator of the vacuum tube audion ty Referring to Fig. 2,24an'd 25 are the usual 35 alternating current supply mains and are connected to the primary coil T, of a transformer which has three other coils on the same ironcore T. vCoil T has many more turns than the primary and operates as a step-up transformer generating a high voltage d1fi'erence at its terminals. Each terminal is connected to the anode or plate of thermionic rectifiers R, and R which permit current to flow in one direction only, viz, from plate to filament. Current to heat the filaments of the rectifier tubes is furnished from a third coil T wound with a sufficient number of turns to produce an induced voltage of'proper amount. The cenconnecting the center point of the coil a nearly constant voltage is available which is practically equal to half the voltage at the terminals'of coil T. It is this constant voltage that operates the oscillator to be later described. The coil T supplies cur-- rent 'for the filament of the three-element vacuum tube 0-.
The oscillator unit is the A enerator' of high frequency currents whic converted into sound waves at the pitch andamplitude required for the purpose of the invention. The operation is exactl the same as-that of any "vacuum" tube an ion oscillator and'consistsin supplying the three- 195 element vacuum tube 0 with a high voltage to its anode through the coil L A magnetic field will be set up in this coil due. to the anode current and will react in coil L to induce a voltage in it. This voltage will are later he impressed upon the grid of the vacuum tube and, as the potential of the grid controls the assage of current in the anode cirother terminals connect to the cuit, it Wlll be apparent that steady oscillations will be generated in the coils L and L and condensers C--1 to C-7,'the perlodicity of these oscillations depending upon the values of these parts. In order to isolate the grid "from. the high voltage of the anode circuit the condenser C-8 is provided. The capacity of this, condenser is-very large and therefore its reactance to the oscillatin current. is very low at high frequencies, hut-it has infinite reactance to the dlrect current of the anode circuit. Switches, are provided to connect in the proper condensers for any potential of coil T 'These con ensers operate in conjunctionwith L,-to. suppress any" undesirable irregularities .in the anode. cur
rent from the alternating current converter and thereby cause other vibrations than those desired to be heard when the set 1s 1n operation.
When the switch S is closedthe alternating current in coil 'I sets up avarying magnetic field in the core T. and the secondaries will each have induced in them voltages depending uponthe number of turns. Alternating current from coil T .will pass through the rectifiers R and R 'The filaments will be heated by a current fiOWlIlg from T The oscillator filamentis heate from coil T The rectified alternating cur-' rent willthen flow from the center of coil Kid oscillating current. 5%
' mined fundaimental.
are a series of condensatlo'ns and rarefac- T, through L, thereby energizing magnet I and thence through oscillator O01l L to the vacuum tube 0 and back to- '1 through the common connector'between coils T, and T Theoscillations in L L and L and the condensers C-l to 0-7 are thus established. Due to these oscillations a magnetic field will be set up. in L, which will change'lts direction with each change in direction of the The diaphragm D will therefore oscillated in the manner previously described to produce air waves oi any required high frequency'. I
Each of these devices Wlll produce rhyth-a mical waves which produce the effect of sinusoidal waves in that they contain a suf of the" predeter ficiently large percents ound waves in air tionsor variations in pressure, and these audition through extended treatment.
int of'zero variations inpressure operate upon the ear drum and its accompanyin mechanism to cause the sensation of soun The arrangement shown in Figs. 1 and 2 may beused either for the correction of defective audition while the person is within the influence of the sensitizing wave or for therapeutic application to correct defective the first pur ose relatively low energy,"such as of the or er of five or ten watts, s used,
while'for the second purpose much higher powers, as for exampletwo to three hundred watts. may be needed.
It is quite 'racticable to employ vacuum "tube circuits tor the generation or low fre- .quency oscillations, but the apparatus is more complicated and cumbersome due to For.
the necessity of using large values of inductance andcapacity. v
.I-believe I am the first to propose the correction of defective audition by means 'of a device which conditions a deaf ear to respond to sounds which are heard by the normal ear and not otherwise heard intelligibly by the defective car. My invention concerns conditioning the defective ear for hearing by pervading a region in which the'hearer is located with practically unnoticeable waves of predetermined frequency, and amplitude, which I have. proven to be efiective or this purpose. All other means disclosed in the art employ devices for conditioning the sound waves for reception by the defective ear either through volume collection or amplification'of the original sound. 7 Accordin'gto my invention, instead of magnifyingthe sounds to be heard, I-improve the sensitlveness of the receiver, that 13 to say, the receiving ear mechanism. In practice of my invention, by means-of a suita-blede-,
vice I cause to be freelye'mitted into space about the person ofdefective hearing the sensitizing waves. The volume of s ace sensitized for correcting audition wil or course depend somewhat upon the size of the diaphragm or other suitable device employed to produce air waves, likewise the amplitude of the wave as generated will affect the d-istance'of its useful employment. I find howeverthat the waves generated by the apparatus I have described herein are 'efiectlve over a very considerable area. A
' diaphragm of twelve inches or less will sen-.
sitize 'under proper conditions of application, the largest auditorium, and a. six inchdiaphragm has served satisfactorily at a distance of thirty feet out of doors.
It is well known that many persons of defective hearin can hear loud sounds. Based upon this fact various devices have been constructed to aid audition, comprising in principle sound collecting devices such as ear trumpets and sound amplifying devices on the principle of the telephone transmitter noise conditions, for example some persons of defective hearing unable. to hear normal time speech under ordinary conditions, can.
While riding on a railroad train hear ap parently better than persons of normal aud1- tion' under like conditions.
'Under such circumstances thedeaf erson hears because the amplitude of the noise vibrations is greater than that of the'normal or ordinary voice vibrations which the deaf person can not hear. Similarly, according to my invention, the amplitude of the substantially IlOiSGlQSSl/lbl'ilhlOIlS produced is greater than those which "would occur in normally audible sounds, I and accordingly theear mechanism of the person hard of hearing is subjected to pressure variations greater than those occurring in normally audible sounds. l have established the fact that the necessary condition to make deaf ears responsive is amplitude of air Wave vibration, and that it is not'necessary to accomplish this with a wave which creates a noise or even an audible sound. 7
While I have described particular forms of apparatus which have been developed by long experiment and have been found to be suitable for the purposes of my invention,
aeratorit is to he understood that other forms of apparatus which operate in a similar Way to produce similar results are Within the scope of my invention.
As a continuation in part of this application I have filed application Ser. No. 204,148, July 7, 1927,
ll claim: p
1. A method or improving the acoustics or audihility qualities of a predetermined space for persons of dificult hearing therein, which method consists'in maintaining in the atmosphere of said space a continuous succession of rhythmical air Waves of such amplitude as to cause pressure variations greater thanrthose occurring in normal unamplified sounds, the said-Waves having a frequency adjacent the marginal frequency of the audible range.
2. A method oiimproving the acoustics or audihility qualitiesof a predetermined space for persons of defective hearing therein which method consists in maintaining in the atmosphere of said space a continuous and sustained succession of airwaves 011 such force'producing characteristics as to cause pressure variations greater. than those occurring in normally audible sounds, the said waves being of such frequency as to be substantially inaudible.
In testimony whereof, l affix my signature.