US 2368953 A
Abstract available in
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Description (OCR text may contain errors)
Feb. e, 1945.
P. J. WALSH ELECTRIC CONTROL SYSTEM Filed Aug. 26, 1940 2 Sheets-Sheet 1 FIGURE FIGURE 2.
Q Pr) l Frequency aSf Feb. 6, 1945. p, J, WALSH 2,368,953
ELECTRIC CONTROLT SYSTEM Filed Aug. 26, 194g 2 Sheets-Shea?I 2 l ENTOR FIGURE 5.
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l:ll-fio? Frequency Patented Feb. 1945 'STATES l PATENT (i1-Fica 3 Glaima.
'Ihis invention relates to a control system actuated by sound waves.
It is one of the objects of my invention to provide a selective control system which can discriminate sharply between desired and undesired sound waves.
It is another objectof my invention to provide a sound wave operated control system for national defense purposes.
It is well known that the characteristic noise" made by the driving engine, propellers and air exhaust of the under-sea torpedo can be heard by means of hydrophones at a distance of several miles from the moving torpedo. It is also understood that if a small depth bomb is exploded under water within a radius of flfty feet of the moving torpedo that such a shock will turn it ofi its course, crush its thin wall, break and stop the delicate driving machinery, or trip its firing fuse mechanism and cause it to explode andA destroy itself. That is, the depth bomb does not have to strike the torpedo but merely explode in the mater near it. It is a simple matter to mount a number of automatic depth bomb throwing guns on the deck of a ship and arrange them electrically so that when ya switch is closed they all re simultaneously and throw ten or more streamlined depth bombs into the water on each side of the ship and at a distance of about fifty yards therefrom.
'I'hese depth bombs can be constructed so that all of them explode simultaneously at a depth of about twenty feet below the surface of the water. If the guns are arranged to throw the depth bombs into the water, along a line parallel to a line drawn from bow to stern on the ship, and spaced about fifty feet apart, the power waves generated by the explosions will merge and form a protective wall around the ship" directly in front of the advancing torpedo to destroy it at a safe distance from its target. All this, of course, depends upon closing the nring switch at the correct instant of time.
It is accordingly one of the objects of this invention to provide an automatic control system that will stay on guard continuously and close the fire control switch at the correct instant of time.
My invention possesses many other advantages and has other objects which may be more easily apparent from a consideration of one embodiment of my invention. For this purpose, I have shown a few forms in the drawings accompanying and forming part of the present specication. I shall now proceed to describe these forms in detail, which illustrate the general principles of my invention; but it is to be understood that this detailed description is not to be taken in a limiting sense, since the scope of my invention is best dened by the appended claims.
Referring to the drawings: Figure 1 is a wiring diagram of one form of my invention;
Figure 2 is a wiring diagramof a further modiilcation; y
Figure 3 and Figure 5 are drawings for facilitating explanation of the invention;
Figure 4 is a wiring diagram of a modification.
The charts shown in Figures 3 and 5 can be drawn directly from the photographic record produced by an instrument known as the Electrical harmonic analyzer." This instrument is described on page 88 of the textbook, Speech and hearing," by Harvey Fletcher, Ph. D., and published "by-D. Van Nostrand Co., New York, as follows: Y
In using this instrument to analyzev sound waves, a condenser transmitter is used to transfer the acoustic wave into an electrical wave which is a faithful copy of the original. This electrical wave is then sent into a selective network, the essential feature of which is a sharply tuned circuit whose frequency of tuning is controlled by varying its capacityzin small steps by means of a pneumatic apparatus simila'r to that used in a player piano. Maximum responses of the circuit occur at frequencies of tuning which coincide with the frequencies of the components of the complex wave. An automatic photographic recorder registers as a permanent record the amount of current getting through the tuned circuit at each frequency. From this record the relative amplitudes of the components of the complex wave are readily determined.
In Figuref3 the upper chart is the acoustic spectrum of the vowel sound O as inton, pitch 268, while the lower chart is a spectrum of still further the vowel sound A as in tapa pitch 250.
These charts show that these sounds contain 17 different frequency bands for "0 and 18 for A. Also they show how the total energy is distributed over these bands. The chart shown in Figure 5 is the acoustic spectrum of telephone line noise. All the components except one are harmonics of aI cycle fundamental and produce a hum like a musical tone in a telephone receiver.
It iswell known that a single musical note contains more than one frequency. The lowest frequency is called the fundamental which usually When no denite which can be a condenser transmitter, hydrophone, microphone or any other'kind oi' device which translates sound waves into electrical waves, is connected by means oi conductors 2 and 3 to the input terminals 4 and l of the multistage dlstortionless vacuum tube amplifier 8. 'Ihe output circuit of amplier 6 is connected by means oi' conductors 1 and 8 to the bus bars 8 and I which can be made of any length as indicated by the dotted lines, to accommodate any predetermined number of band pass filters such as 20. The input side of the band pass lter 2l is connected by means of conductors 2i and 22 to the bus bars 9 and Il, and its output side is connected by means of conductors 23 and 24 to the input side of the variable distortionless attenuator 25. The output side of attenuator 2l is connected by means of conductor 26 to one side of condenser 21 and to one end of the relay coil 28, and by the rectiiler 30. The other side of the rectifier 30 is connected by conductor 3i to the other side of condenser 21 and the other end of relay coil 28. It is seen that there are ive groups exactly the same as this. That is, the band pass filters 29', 30', 3l' and 32 have their input side connected t0 the bus bars 9 and I8 and their output side connected to the attenuators 33, 34, and 36 respectively. The output sides of the attenuators are connected through the rectiilers 31,'38, 39 and 40 to the condensers 4I, 42, 43 and 44, and the relay cOilS 45, 4S, 41 and 48.
means of conductor 29 to one side of Y As the description proceeds I will explain how A a complex wave picked up by the translating device l is amplified lby the ampliner s, applied to the bus bars 9 and l0, separated into its component frequency bands by the band pass illters, the components applied to theattenuators which absorb a predetermined amount of energy, the alternating current output from the attenuators changed to direct current by the rectifiers and lter condensers and passed through the relay coils to close the relay contactors which form the control circuit.
In order to adjust the apparatus to respond `to a desired sound, as for example, the lower chart shown in Figure 3, which shows 18 bars oi different amplitude, we proceed as follows: The band pass iilter 20 is tuned to pass the narrow band of frequencies indicated -by the rst bar on the graph including 250 cycles, the filter 2l' is tuned to the frequency of the graph including 500 cycles, the lter 3l' is tuned to the frequency indicated by the third bar and the lter 3i' is tuned to the frequency indicated by the fourth bar on the graph. This process is continued, there being as many illters as there are bars on the graph, until we come to the last bar to which the filter 32 is tuned. The adjustment of the attenuators is determined by the amplitude of the bars. The attenuators 25, and 34 are adiusted to give maximum loss since the rst three bars on the graph indicate relatively high energy while the attenuator 35 is adjusted to its low. loss position, since the fourth bar is relatively small. This process is vcontinued, there being one attenuator for each bar on the graph, until we come to the attenuator 36 which is adjusted to its low loss position as second bar on the indicated by the last bar on the graph. Bince al1 the relays and their rectifier lcircuits are identical, any one of them will respond when the current flowing through its coil reaches a given value. i
When sound waves represented by the spectrum. show in this chart are picked up bythe translating device l, amplified by the amplifler 8, and applied to the bus bars 9 and il as alternating currents, currents at a frequency to which the band pass filter 20 is tuned pass through the attenuator 25, while'currents at other frequen- -cies are rejected. Some of this current is lost in the attenuator resistors and the rest passes on over conductor 29. through rectifier Il to filter condenser 21, relay coil 28 and back over line 2l to the resistance network of attenuator 2l. Current cannot iiow through this circuit in the opposite direction due to the action of rectifier 3B. Currents iiow through all the filter-attenuatorrectier-relay units simultaneously, each band pass filter rejects all frequencies above and below the band to which it is tuned allowing only those currents at the frequency'to which it is tuned to pass on through the connected attenuator, rectier and relay coil. When the current flowing through the magnet coils, such as, 28, 4l, 48, 41 and 48 reaches a predetermined value the contactors lll, il, 52, 53 and 54, which are held in the position shown by a spring, are drawn over intocontact with the contactors 5I, 58, 51, I8 and 58 respectively. 'Ihus the control circuit between the terminals and 6| is closed. It is seen that all the contactors must be closed in order to close the circuit between terminals 60 and il and that any one of these contactors can open this circuit. In other words, the terminals 80 and 61 are the terminals of a switch which closes whenever sound waves of predetermined characteristics are picked up by the translating device i, and opens when these waves die out. It is obvious that this switch would not be closed if the translating device I picked up a sound wave having the characteristics shown in the upper chart of Figure 3, since the bars diiier in frequency and in amplitude.
While the second bar in the lower graph represents a band frequency very close to, and partly overlapping the band frequency indicated by the second bar in the upper. graph, there is not enough energy in this upper frequency band to overcome the high loss in the attenuator 33 and close the relay contactors 5| and 58. It thus comes about that the selectivity, or ability to discriminate between desired and undesired sound waves. is obtained by the combined action of the attenuators and filters and not by the illters alone. 0f course, complex undesired sound waves may contain a number of frequency bands identical to those of the desired wave, and therefore, would close some of the relay contactors, but ce all the individual contactors must close in order to close the circuit between terminals 8|! and 8l, the selectivity factor is very high indeed.
When the device must operate near a source of continuous noise, such as that generated by running machinery, a great deal of this interference can be eliminated by employing the form ci input arrangementshown in Figure 2. Referring to Figure 2, two translating devices l2 and 83 are shown mounted on opposite sides of the large baille 84 which can bemade ot any convenient shape and may be a. sione wall, building, or the hull of a ship the outline oi' which is shown in vthese waves simultaneously and translate them into electrical waves. The electrical waves generated by hydrophone 82 pass over the conductors 65 and 66 to the input terminals of the amplier 61; those generated by the hydrophone 68 pass over conductors 68 and 89 to the input terminals of the amplifier and phase changer 10. The elec' tronic emission device 1| having the anode 12, cathode 13 and the grids 14 and 15 is of the coplanar type having one-of the grids wound between the meshes of the other grid. The plate battery 16 maintains the anode 12 at a potential positive relative .to the cathode 13, the battery 11 maintains a negative bias on both grids and the battery 18 furnishes current to heat the cathode 13. Since the operation of such devices is now well understood further detailing thereof is unessential except to point out that when electrical impulses are applied to either grid and cathode, they reappear across the output terminals 19 and 80 as amplified impulses; but no impulses will appear across the terminals 19 and 80 when electrical impulses are applied to one of the grids and cathode while impulses 180 degrees out of phase therewith, but otherwise identical, are applied to the other grid and cathode. This is obvious since, under such circumstances, one of the grids would tend to increase the space impedance of the device 1| while the other grid tends to decrease it by the same amount.
I will now explain how the waves generated by hydrophones 62 and 53 due to undesired noise are applied to the grid 14, and simultaneously to the grid 15 exactly 180 degrees out of phase therewith, so that they do not appear across'the terminals 19 and 80 while the desired waves are amplied and do appear across these terminals.
'I'he grid 14 is connected by conductor 8| to one of the output'terminals of amplifier 61 and the other output terminal is connected by conductors 82 and 83 through the bias battery 11 to the cathode 13. Grid 1.5 is connected by conductor 84 to one of the output terminals of the amplifier and phase changer while the other output terminal is connected by the common conductors 82 and 83 through the bias battery 11 to the cathode13. By adjusting the gain control and phase changer of amplifier 10 the potential iluctuations applied to the grid and cathode 18 due to undesired noise are made equal to, but 180 degrees out of phase with those applied to the grid 14 and cathode 13 by amplifier 61. Thus sound waves generated near the stern of the ship by the propelling machinery are balanced out, but waves picked up by either one of the hydrophones 62 or 63 from any other source are applied to either one of the grids 14 and 15 and appear across the terminals 19 and 80. Also a source of sound at any position other than the stern of the ship will affect one hydrophone to a greater extent than the other, and therefore, one of the grids 14 or 15 will be affected to a greater extent than the other and these impulses will the drawings. To facilitate explanation oi' this 3' can be disconnected from the terminals 4` and 5 and terminals 19 and 80 connected throughv y 3 appear across the lterminals 19 and 80. From here on the apparatus is the same as that shown in Figure l. As a matter of fact the wires 2 and the proper impedance matching device to the terminals 4 and 5.
In the form of the invention shown in Figure 4, the desired sound is rst recorded on a sound film or phonograph record.\ This record is then analyzed by means of the Electrical harmonic analyzer and a chart drawn such as those shown in Figures 5 and 3. The record is then placed in the reproducing device 85 where the recorded sound waves are converted into electrical waves in a wel1 understood manner, the record running continuously, reproducing the recording over and over again. One reason for thus analyzing the record is to determine the overall frequency range and the number of pairs of lters required. The
reproducing devicel for example, may be a band of sound record film driven as a continuous belt around pulleys, with a photoelectric pickup, such as described on pages 6 to 45 of the Electrical' Engineers Handbook, volume'5, by Harold Fender, published by John Wiley and Son, Inc., yNew York. By means of the chart the band pass filters 86, 81, 88 and 89 are tuned to correspond to the frequency bars on the chart as has been described in connection with Figure 1. i These filters are adjusted in pairs, that is, the lters 86 and 81 are tuned to one band frequency as indicated by a bar on the chart, while the filters 88 and 89 are tuned to a different band as indicated by another bar on the chart, etc., there being a pair of band pass filters for each bar on the chart.
fIhe electrical impulses from the reproducer `85 pass over the conductors 90 and 9| to the input terminals of the amplifier 92 where they are amplified and reappear across the output terminals to which the bus bars 93 and 9-4 are connected. The bus bars can be made of any length as indicated by the dotted lines to accommodate any number of band pass filter units. The output Icurrents from the amplifier 92 flow over the bus bars 93 and 94, and those at a frequency to which the lter 81 is tuned pass through it into the rectifier-relay-condenser circuit 95, 96, 91; while the currents atl a frequency to Iwhich the filter 89 is tuned pass through itinto the rectier-relaycondenser circuit 98, 99 and |00. This direct current flows through the magnet coils and draws the contactors |0| and |02 over to the iron cores of the coils and away from the contactors |03 and |04 respectively, where they were held by a spring, and thus'opens the control switch circuit between the terminals |05 and |06.
If an undesired sound is picked up by the translating device |01 and contains a frequency band to which the filter 86 is tuned, the contacter 0| will not return to the position shown in the drawings unless the current owing through the rectifier I5 and magnet coil |08 is at least equal in value to that flowing through the rectifier and magnet coil 96.
When desired sound waves affect the translating device |01 they are converted into electrical waves which flow over conductors ||0 and to the input terminals of amplifier ||2. The amplification of amplifier ||2 is made suchthat the ampliiied Waves impressed on the bus bars H3 and ||4 are identical to those impressed on the bus bars 93 and 94 by the record 85. Since the lters 86 and 81 are tuned to the same frequency and the circuit elements connected .to each lter 4 Y assauts pairs of units connected to the bus bars like the twopairsshowninthe drawings. o l l In order to adjust this formk of the invention to z f f act as fire-control of a battery of automatic depth pbomb'throwingguns, weproceed as follows: l The l ship in which ther apparatus is installed'is taken. out on the range and the engines stopped tor a recording .,oi'. the sound. generated by astandard moving torpedo, preferably one constructedalong y the lines of those employed by the enemy power. f The torpedo canbe fired :from a deck tube of a destroyer anchored at a predetermined distance/- Y from the ship ,and along aline parallel to the l ships side at a given distance therefrom, `A chart l l is made from this recording and the band pass filters adjusted ink the usual way. The 'ship is f l then given a fullspeed ahead run over the rangek l and when it comes to the'spot lwhere the ilrst .recording was made. the anchored destroyer fires the torpedo (which was recovered afterthe rst shot) again over the same line and a recording of the noise made by the ships propelling machinery plus that generated bythe torpedo is made. This record is then'y placed; in the repro'- ducer 85,.
` -When the ship is at sea thehydrophone |01 is ailected by the noise imade by the ships propelling l machinery and applies these waves to the ampli- Lner, I I2, but since thisnoise is` recorded, the ref producing ldevice 85 applies similarwaves to thek amplifier 92, so that, if this noise contains any frequencies thatv can 'get throughlany of the iilters, these are'balanced fout in the diirerential open the` contactors, such as IOL ilred at the ship, the intensity of the received sound gradually buildsup as the torpedo advances ,Y toward the ship, causing the direct current ilowing through the coils, such as IDB, to gradually build up, and when this current reaches the value of the current owing through the coils, such as 96, the contactors, such as IUI, move to the position show jn in the drawings. Thus the nre-control switch between the terminals |05 and |06 is closed 'when the advancing torpedo is at a pre-A determined distance from the ship. If thecrude speed f 1.o! the .torpedo is :taken as 60 miles per hour, or
88 feet per' second, this is very slow. indeed when comparedwith the velocity of sound through the Water which is about-5,000 feet per second. l I claim: f y
1.k In combination, a source oi' both desired and quency but unequal energy content, ka rplurality of means tuned to the component frequencies of the desired waves only, means associated with said tuned means for absorbing energy from said .com-
v ponents to enable amplitude discrimination between desired; and undesired components oi like frequency but unequall energy. content, means frequency bands adjusted to pass energy within .f 'n
its particular narrowefrequencyband only; means for transi'ormingsuchzsound wave into a correspending electric wave and feeding same to said'r n lters in parallel; a circuitto be controlled, in-
n yciuding a series fofelements normally occupying 39 positions which render said controlled circuitinr operative and individually requiring at least a l predetermined amount of energy to shiItthem-to positions which render the circuit operative; fan
attenuator associated' with each of said illters to '35 receive theoutput therefrom, each of saidattenuators being adjusted in accordance withfthe f energy content ofk its associated frequency band to s0 position in said controlled circuit; and means yfeeding. the output lof each attenuatorto one of said series of elements.
3. The method of controlling a circuit in response to a wave having a characteristic frequency spectrum Whose frequency components are of non-uniform energy content, which comprises splitting said wave into its characteristic Irequency components, absorbing from each component a predetermined portion of its energy content in accordance with the energy content of such component, to leave a residual energy of a substantially common value as to all components, and energizing with the residual energy' of each frequency component, one oi' a plurality of similar 55 series connected elements in such circuit.
PHILIP J OH'N WALSH.
`undesired waves: including components of iikeirewhereby each desired component affects an elepasssuillcient energy ifrom .its associated filter to shift oneof said series of elements to itsoperative f