US2079620A - Direction finding - Google Patents

Description

May 11, 1937. w KUNZE 2,079,620

DIRECTION FINDING Filed'Feb.A21, 1931 2 Sheets-Sheet 1 26 y 27 s s i? 3 Inl/enrich Dn /z'lly Kanye Perfl/MW?? Jl tt orne'u.

May 11, 1937. WgKUNZE v2,079,620

DIRECTION FINDING Filed Feb. 21, 1931 Y 2 sheets-sheet 2 37 u y Figure 4' DZ fe/'liar Dr. willy- Kunj'e bothears 'ments which I have observed certain advan ages are presented in the use of the maximum method' Patented u May Y 11, 1937 Willy Kunze, Bremen, G

'marine Signal Company,

poration of Maine Application February 21,

April 30, 1930 In Germany ermany, assigner to Sub- Boston, Mass., a cor- 1931, SerialNO. 517,510

Claims. (Cl. 177-386) The present invention' relates to the art of determining :the direction of a source of compres# sional waves; and more particularly to sound waves propagated in air or water medium in which a group Aof sound receivers are used and in which the sound energy arriving at each receiver is brought-into the same phase at the indieatingv device. In arrangements of this nature it is common practice in the art to use a group of electrically responsive acoustic receiving dvices spaced'apart ina definite' geometric configuration a'nd conduct the electric energy created by thesound waves arriving at each receiver through retardation lines to a pair of telephone devices or 'an indicator.v In lsuch apparatus theY retardationv lines form a so-called electric compensator in which a switch mechanism is provlded to compensate for a variation ofthe direction of the wavefront arriving at the receivers.

y In this way, it is possible to turn the compensator .switch mechanism until the receivers are compensated for any particular direction of the wave front. When the receivers are so campen# sated that the wave front for which they are adjusted" corresponds to the actual Wave front of 25. the sound being received, a maximum sound intensity is present inthe telephones or listening devices.- Y

In the ypast in such apparatus two methods of compensation 'have 'generally been used, one in which the observer notes the position of the 1 binaural image and the other in which the obserjvatlon is made by observing the maximum sound intensity.

3 In systems employing the so-called binaural method the receivers of one group are connected is actually distributed over an angle subtending ,ship is approximately in the same line, or nearly the same line, it is almost impossible to distinguish the diffrent vessels and set upon each separately with the maximum method. The sounds of the two vessels blend to-. gether over the angle betwen the two vessels from the listening source and it is practically impossible to obtain a true setting of the maximum intensity of the sound from any one-of the vessels. This might naturally be expected since the sound l0 the line of the two vessels from the listening source. In these cases the binaural method of listening often vproves very advantageous since the sound image of each'vessel is4 independent l, and separable from eachother, and although other disturbing sounds may be present, there will be a distinct shift from a lateral to a central image of one group of sounds even though the other group are present in the same field.

I have found, however, that by the use of a 20 highpass filter the field of each individualvessel may be considerably narrowed and if the other vessel is not within this narrow range, a setting by the maximum method may be made. Where, however, the two vessels are positioned in the same narrow field according to my invention the filter is dispensed with and the binauralmethod sels from the listening used.

with one telephone going'` to one of the ears of the observer and the receivers ofthe other group are connected to a second telephone going to the other ear of the observer.

With the maximum method, on the other hand,

the receivers are all connected to both telephones so'that the same mixed sound wave arrives at of the observer. According to e and certain other advantages are presented in the use of the binaural method. D The combination of these advantages in a sin- .50 'gie-devicefor the purpose of determining the direction of' a source of sound'or compressional passes.Y

.of all frequencies reach the In view of thev fact thatA the elimination of the lower frequency sounds sharpens the maximum intensity, it is possible by this method to obtain a much more accurate setting and observation of the direction of the source of sound waves. In employing this feature it is possible to listen, first, without the use of a filter in which case sounds ears of the observer of the indicating device, and it is then possible, after the character of the vessel has been deter.- mined by listening to the natural sounds, to cut 40 out all the sounds ofthe lower frequencies and accurately determine the direction of the source with only the higher frequencies. I have found in some cases that the use of av filter diminishes the sound intensity arriving at the indicating de- 4, vice. This is perhaps particularly true where the greater part of thesound source is made of sounds of lower frequencies from that which the filter In such cases an amplifier is used in connection with the. lter to bring up the sounds to 5| normal Value.

,wave is the Vsubject .matter of the present invention.

` In particular, in listening to a number of vessels in thesame field, where the direction of the'ves- The filter usedin-the present invention may be' -one which passes frequencies above eight hundred cycles, but I prefer ir most cases to use a highpass filter which has a higher cut-off, for in- 5 the filter stance, at fteen hundred cycles. It is very diiicult to obtain a binaural setting for frequencies'above fifteen hundred cycles, and in this range, therefore, the maximum-minimum method is most effective.

Y The present invention will be described in particular in connection with the drawings in which Fig. 1 illustrates the sound intensity field with both low andv high frequencies present, Fig. 2 illustrates the sound intensity field with thel use of av high-pass lter, Fig. 3 shows schematically a circuit arrangement and Fig. 4 shows a modification of the circuit shown in Fig. 3.

In Fig. 1 the line 4IJ',` having dots I, 2, 3, 4, 5 and 6, indicates the receivers arranged along this line on the dots just mentioned. 'I'he curve 'I in this case shows the relative intensities with which sound is received coming from a direction in the same plane as the plane of the paper. For instance, a sound coming from the direction of the line 9, I2 will have an intensity corresponding to the vector value of the length 9,' I2. A sound coming from the direction 9, II will have the intensity corresponding to the vector length 9, II.

In Fig. 2 where the curve 8 corresponds to the curve 1 with the exception that the lower frequencies'have been cut out'by the lter, the line I0, I4 shows the relative intensity of the ysound received from a direction of III, I4. Comparing Figs. 1 and 2, if the vector lengths I0, I3 and I0, I4 are the same as the vector lengths 9, II and 9, I2, respectively, the figures indicate that in the case of Fig. 1 for the decrease in the same intensity of sound the angle is u' while in Fig. 2 -this same angle is a. In the case of Fig. 2 the intensity drops oil' quickly wi-th small variations in angles, whereas in Fig. 1 it drops off much more slowly. i

With the use of high-frequency filters, there is often present secondary or auxiliary maximum in the shape of small lobes similar to the lobes of 8 in Fig. 2. These lobes are apt to cause an ambiguity of direction and this is overcome in the present application by the use of the binaural method as 'a check to eliminate these ambiguities. The binaural image will only be produced with the maximum lobe so that if the compensator is set on a secondary lobe, this will easily be determined by switching to the binaural method which will indicate whether a binaural image is ory is not obtained.

In Fig. 3 there is illustrated diagrammatically by I, 2', 3, 4, 5 and 6 corresponding to the same numerals in Figs. 1 and 2. If the group of receivers I to 6, inclusive, are rotated about an axis 90 so. that their line is made to coincide with the wave front of the approaching sound, the electrical energy in the circuit 2l connected to the receivers I to 6, inclusive, through the transformers I to 20, inelusive, respectively, will be impressed upon the telephone 22 either through the filter indicated as 23 or over the straight transmission line 4I. The lter 23 comprises the inductances 30 to 33, inclusive, in shunt and the capacity 26 to 29, inclusive, in' series between each shunted inductance. Switches 24 and 25 are provided to throw or the transmission line in between Vthe telephone 22 and the `receiving circuit 2 I In Fig. 4 `the complete arrangement of the circuit in which a compensator using either the binaural or the maximum-minimum method and a filter and an amplifier associated together is shown..- In this figure the receivers are indicated `to the right, both telephones shown a group of 4six receivers .tardation lines 44 and 45. 5, inclusive,

In this system, therefore, the eiective binaural` base is a distance between-'two adjacent receivers. The system just described is chosen because this will give a sufficient binaural base to be used in checking the true maximum from auxiliary max# imum and'also iniaiding the determination of the direction of a source of sound when the two vessels are in the same field.

A proper switch dicated by 46 and 49, 50, 5I, 52 and 55, 56 and 41, to adjust the contacts 48, corresponding contacts 53, 54, at various points along the respecfrom listening which includes the mier 23 and the ampliler A in front of the telephones 62 and 63. The amplier A is connected to the circuit at the stances the telephone 63 is groupof sound 'receivers while the telephone 62 is operated by the right group of sound receivers. When the switches 60 and 6I are thrown thrown "in parallel and are operated by both reand both groups of receivers.

When the switch 60 is thrown to the right, both retardation lines 44 and 45 are connected through the short leads 80 and 8| to the input point 82 of the filter. It will be noted that the common 83 is at all times permanently connected on one side to the Iamplifier .as at 84 and on the other side to the common lead to the right and left headphones 62 and 63. The output lead 86 of the lter with lthe common 84 form the input to the-amplifier. The output to the amplifier, leads -81 and 88, when the switch 6I is-in the position shown in Fig. 4 to the head telephone throughthe leads 88 and90, respectively. In this arrangement just described' both the lter and the amplier are in circuit and the two telephones are connected in parallel, -botlreceiving the. same input and therefore. providing onlyV a,

The compensator 'shown at 43 is,

mechanism is provided, as in- I operated by the left v 62 vand 63 are on the right lead 64 and the left lead 64, re-

` justment on the I multispot listening spectively.` The leads 64 conduct the impulses through the switch 6l to the telephone head pieces 62 and 63 by'means of the leads 89 and 90. The common 83 remains as before connected to the common to the two telephones. In this position the telephone 63 is connected to the retardation line 44, and the telephone 62 to the line 45, and a binaural listening is therefore possible.

In the method employed in the present case, the operator can either listen, first, by the binaural method or by the maximum method. If he listens by the maximum method, he preferably may use the filter 23 and the amplifier A to amplify the 4high-frequency sounds which may be somewhat weak if they are not the predominant frequencies from the listening source. In order thereafter to determine whether any ambiguity of direction exists, he may throw the switches 60 and 6l to the left and check his observation by the binaural method.

This is perhaps the preferable manner of operating the present system although it is possible and perhaps under certain circumstances desirable to employ the binaural method when the vessel to be vessel. In this case the binaural method may alone be employed or the binaural in combination with the maximum method may be employed as described just above.

There are a number of advantages i'n first determining the approximate directionof the source of sound without the use of a filter and then using the filter in the final steps. Since without the use of the filter the true character of the sound is more clearly observable, it is possible frequent- 'ly in cases where more than one sound is in the llistening eld to concentrate on one of the sounds for an approximate setting and then complete the observationby a more accurate adsoundwhich is first observed. In this way even though two sounds are somewhat near together as, for instance, when two ships are within the listening range of the apparatus within a few degrees of one another, it is frequently possible to make an accurate determination of the position of one eliminating the position of the other.

In addition to this, however, a further ad'- vantage is obtained in making an approximate determination initially without the use of a lter. While the filter image to a considerable degree, it provides, however, a number of secondary or auxiliary maxima4 which might sometimes be mistaken for the chief maximum if the compensator is set with the filter initially used. Omitting the lter initially, the chief maximum can be readily determined within a number of degrees, and then using the lter, this maximum can be observed very-accurately.

In addition there is a further utility in observing the sound initially without the use of a filter. While most vessels in So-called submarine radiate sounds of practically all frequencies, still it sometimes happens that certain frequencies are not produced. If a vessel did not emit much hig'h frequency sound, the use of a filter initially would make it appear that no. source was within the listening range and may, therefore, be difficult at firstvto detect the source.. In this case the. initial observation is quite important. It is also true that frequently the observed is in the vicinity of another itself sharpens the maximumA maximum with a filter on account of its sharpness will be passed over in making an observation. The maximum without the filter being quite broad furnishes a good initial observation for beginning the accurate determination of the direction -of the source.

Having now described my invention, I claim: I

1. In combination, a plurality of spaced receivers, a pair of telephone receivers, a compensator for bringing the sound received at said receivers into substantially the same phase to produce a maximum sound intensity at the telephone, a filter and an amplifier adapted to be associated therewith at the output of said compensator, and means connecting said filter and amplifier in circuit after the compensator, and said telephone receivers as a singleY unit in the circuit after the other elements when the filter and amplifierare used and connecting said telephone receivers individually at the said output when the filter and amplifier are not used.

2. In combination, a plurality of spaced re-v ceivers, a compensator, means for using said compensator for the binaural or maximum-minimum method, a high pass filter, a pair of telephone receivers connected to said compensator, and means for. connecting the filter in circuit before said telephone receivers in using the maximum-minimum method and omitting the filter in using the binaural method.

3. In combination, a plurality of spaced receivers, a compensator, means for using said compensator for the binaural or maximum-minimum method, a high pass filter and amplifier associated therewith at the output of said compensator, a pair of telephone receivers, and means for connecting the filter and amplifier in circuit between the compensator and said telephone receivers 'in using the maximum-minimum method and omittingxthe filter and am lier in using the binaural method.

4. In combination, a compressional wave pickup system including a plurality o f spaced pick-up units and a telephone means associated therewith, means for adjusting said system to bring the energy at thetelephone means into substantially the same phase and create thereby an observable intensity maximum and means for filtering out the lower wave frequencies from the received energy whereby the maximum observation may be sharpened.

5. A method of increasing the accuracy of determining the direction of a source of mixed sound waves which consists in receiving the waves at a plurality of points spaced from one another, translating the waves so received into corresponding electrical impulses of the same frequency and character, conducting said translated waves to a common point, variably retarding the progress of the waves until said waves are brought in the same observable phase, ltering. the waves brought to the common point to pass only the higher frequencies picked up from the source whereby the accuracy of determination of the phase coincidence may be more accurately observed.

6. A method of increasing the accuracy of determining the direction of' a source of mixed sound Waves 4which' consists first in receiving the sound waves at a plurality of points spaced apart one. from the other, transmitting the energy so received to a common point, variably retarding the time of transmission of the energy to the comto said common point mon point untilall of the energies have approximately the same observable time phase, ltering the energy after retardation to eliminate the lower frequencies from the source that is being observed and further adjusting the retarding of the 5 impulses to make a more accurate observation of the direction of the source.

7. A method of increasing the accuracy `of determining the direction `of a source of mixed sound waves which consists in receiving sound at 10 a plurality of points spaced apart one fromv .the other, transmitting the energy picked up at all of said points to a common center, variably retarding energy so picked up until a maximum intcnsity of energy isl/observed, filtering out the l5 lower sound frequencies of the source listened to after the energy has been retarded and varying the retardation until a sharper maximum is obtained.

8. A method of increasing the accuracy of de- 20 termining the direction of a source of mixed sound waves which consists rst in receiving the sound waves at a plurality of points spaced apart one from the other, transmitting the energy so received to a common point, variably retarding l 20 the time of transmission of the energy to the common point until all of the energies have approximately the same observable time phase, ltering the energy after retardation to eliminate the lower frequencies from the source that is being ob- 0 served and further adjusting the retarding of the impulses to make a. more accurate observation of the direction of the source, the filter being adapted to lter out frequencies below a value not sub- Vand further adjusting the stantially less than 800 cycles arriving from the source of sound;

9. A method of increasing the accuracy of determining the direction of a source of mixed sound waves which consists in receiving the sound at a plurality of points spaced one from the other,-

conducting the energy received at the spaced points to a common center, variably retardlng the time of such. conduction until the energies produce at the central point an observable maximum, filtering out the lower sound frequencies of the source received and adjusting the retardation for a sharper maximum, then listening at the central point by the binaural method to determine whether a true maximum has been obtained.

10. A method of increasing the accuracy of determining the direction of a source of mixed sound waves which consists rst in receiving the sound waves at a plurality of points spaced apart one from the other, transmittingthe energy sc received to a common point, variably retardlng the time of transmission of the energy to the common point until all of the energies have approximately the same observable time phase, ltering the energy after retardation to eliminate the lower frequencies from the source that is being observed retarding of the impulses to make a more accurate observation of the direction of the source, the lter ltering out all frequencies below 1500 cycles whereby the frequencies o f the sound source above this value are observed.

WILLY KUNZE.

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