Патент USA US2121941код для вставки
June 28, 1938. ‘ <5. WURDEL ' ‘ 2,121,941’ sounn 'rmmsmmme APPARATUS Filed June 12, 1935 .. . 2,121,941 Patented June 28, 1938 / . UNITED STATES PATENT OFFICE 2,121,941 SOUND TRANSMITTING APPARATUS ‘ Giinther Wurdel, Berlin, Germany, assignor to Apparatebau Gesellschaft Neumann & Borm Kommanditgesellschaft, Berlin, Germany imman- June 12, 1935, Serial No. 26,271 In Germany August 25, 1934 I 10 Claims. (01. ria-ms) This invention relates to a sound-transmitting apparatus for telephone systems. The primary object- of the invention is to pro vide a telephone for vuse under conditions ‘where 6 by a telephone of the oridnary kind will not give satisfactory results owing to interfering noises, as for instance in the engine rooms of ships, in air ‘.craft, or in numerous other instances in which prevailing noises will completely drown the voice , 10 of the person speaking. A further ‘object of the invention is to provide a microphone free from chattering effect and hav ' ing a practically straight characteristic which is devoid of resonance in the audible range. 15 By chattering effect is meant the reverberatory ' effect or non-linear distortion which arises in the case of ordinary telephone microphones due to the fact that, owing to the mechanical natureand v disposal of the diaphragm, the movement of the. i0 diaphragm is not equal on both sides. A still further object is to provide a telephone in which the effective surface of the microphone, whilst in other sounds an exaggerated emphasis on the initial part of the sound causesa com plete distortion of the tone. ~ To avoid the disadvantages associated with . laryngeal microphones attempts have been made‘ 5 t' to employ microphones which are excited by sound in the air, and in which there are provided special auxiliary means, for example screening or damping means, which have the object of withholding interfering noises from the micro-. 10 phone. Screening and damping means of this kind certainly cause a decrease of the interfering noises at the effective microphone surface, but at , ' the same time they also nullify a part of the voice energy to a similar extent.. Moreover when using 15 ' the microphones hitherto .usual for telephonic purposes it is impossible to hold the same as close to the mouth as would be desirable, as owing to the greatly increased voice energy impinging on the surface of the microphone the distortion of 20 ‘ ‘ the speech would in this case be so considerable as to render intelligibility impossible. These dis when the telephone is in use, is situated in a tortions are caused by the fact that the micro plane passing through the corner of the mouth ' phones, when a certain volume of sound is ex ceeded, are overmodulated. A distortion of‘ the 25 .. of the speaker. A further object is to make provision‘ for exci ‘ speech also occurs when the microphone is ap tation of ‘ the effective surface of the microphone proached too closely towards the mouth because - ‘in immediate fashion by the spoken words. These and other objects and advantages of the invention will become apparent as the description proceeds. _ . It has already been proposed to employ in rooms in which there is a considerable volume of noise laryngeal microphones, which receive the '' speech vibrations by'being placed against the larynx or the lower jaw of the speaker. Even with microphones of this kind, however, it is mereyl possible to a limited extent to preclude the effect of interfering noises. The articulation is also unsatisfactory, because the higher speech os cillations, which are particularly important for proper intelligibility, are, despite the location of the microphone against the larynx or the jaw, in1 the case of the carbon microphones hitherto used for telephonic purposes the particles of car bon do not, as 'a result of the very high exciting 30 intensity, oscillate properly about a ?xed position of‘equilibrium‘, but are thrown out of their origi nal position and do not again return to the same. There then occurs .what I have termed a chatter ing effect. _ ' ‘ ' 35 Assuming an attempt is made so to construct the damping means above referred to that the overmodulation or the chattering effect of the microphone is eliminated,_this will also not lead a to the desired result, as the frequency character- 40 istic of the microphone is not disposed in a ~ straight line but possesses powerful resonance points at numerous points-of the audible range. absorbed by the intermediately disposed skin,‘ Generally speaking, interfering noises are not ‘5 which/acts as a cushion, and in consequence do not ‘wholly reach the microphone. Moreover in numerous spokensounds there is no appreciable . vibration on the part of the jaw or the larynx, Any attempt to overcome the strong drop in the alternating potentials delivered by the laryn geal microphone in the range of the higher speech oscillations by the‘ inclusion of rectifying ele ments between the microphone and the sound re producing means does also ‘not lead to the de 55 sired'resvult, as the drop in the directiontowards the higher speechoscillations'does not take place evenly, i. e., in a straight line, but is disturbed by the fact that in'the case of numerous spoken sounds, particularly sibilant sounds, there is no .0 conduction of the sound on the part of the body, con?ned to a narrow section of the entire sound 45 range. Accordingly, at resonance points of the microphone affected by corresponding interfering ‘ frequencies, the alternating potentials delivered by the microphone increase to such extent that the interfering noise occurs in a much more pow- 50 erful form at the reproducing apparatus than is represented by the ratio between interfering I noise and voice energy at the microphone. It is, ' therefore, impossible to obtain a proper reproduc tion of speech in noisy rooms with the micro- 55 phones of poor frequency characteristic hereto~ fore employed for telephonic purposes. . Microphones are known, which possess a good ,7 frequency characteristic, that is to say-which do not reveal any or any appreciable resonance o0 2 2,121,941 points within the entire audible range. These microphones accordingly reproduce the voice en ergy passed to the same without any appreciable distortion. Their frequency characteristic, there fore, is disposed practically in a straight line, i. e., is devoid of resonance points. These micro , Figs. 3 and 4 are front and side views of the, form of embodiment of the telephone according to Fig. 2, Fig. 4 being partly in section. . ‘Figs. 5 and 6 are front and side views of a modi?ed form of embodiment of the telephone. In the diagram according to Fig. 1_ the curve ’ phones, which may be constructed as contact I a-b shows in millivolts the alternating poten or also condenser or electro-dynamic sound tial delivered by a. microphone approached more transmitters have heretofore been employed for and more towards the source of sound, 1. e., 10 radio transmitters, the making of talking ma chine records and for sound-film purposes, as in these cases it is necessary to attain a very natural reproduction of speech and music, which would be impossible with the carbon micro 15 phones employed in the telephonic. art. Micro phones having a good frequency characteristic have heretofore not been employed at all for telephonic purposes, primarily on account of their small sensitivity, which renders necessary 20 an ampli?cation of the alternating potentials of the microphone. - a It is shown by this diagram that the sound energy in the range of the usual spacing of the effective surface of the microphone from the source of sound, 1. e., in the range of approxi supplied by them. It is quite readily possible, mately 40 to '70 mm., is completely covered by without detriment to the good properties of the same, to construct these microphones in a small size suitable for the purposes of the present in vention. 0f the microphones of good frequency characteristic above referred to the contact sound is greatly approached towards the micro phone, i. e., to within approximately 6 mm., the the interfering energyie-d). ‘ If the source of alternating potential delivered by the micro transmitter possesses a comparatively good sen phone increases in the case of the example shown in the diagram to more than ten times the value sitivity. of the interfering potential. . Now it has been ascertained that microphones 30 of good frequency characteristic also have no chattering effect even if-in departure from the mode of use hitherto usual-the effective sur face of the microphone is approached as close as possible towards the mouth, where the sound 85 output of the speech possesses its maximum value. This necessitates that the microphone, also in contradistinction to the sound transmit ters previously employed for telephonic purposes, does not have a mouthpiece or the like. Hereto 40 fore it has been the general impression that a mouthpiece of the elongated or trumpet variety could not be dispensed with as this served to withhold at least in part the interfering noises and to exert a favorable effect on the frequency, 45 characteristic of the microphone. If, however, in the case of the microphone of straight fre quency characteristic employed according to the invention a trumpet or similar mouthpiece ‘were employed, the column of air enclosed within the 50 mouthpiece and acting as resonator would also be caused to oscillate by some frequency of the interfering noise. The interfering noise audible in the receiver would accordingly assume a dif ferent character in tone, and would be ‘much 55 stronger than would correspond with the in tensity of the sound at the sound inlet aperture. It is known in itself in the acoustical art that the sound output increases approximately ac cording to a quadratic function with approach towards the sound source. It has, however, not been appreciated heretofore that the'sound out-' put assumes in the immediate vicinity of the mouth, 1. e., at the point of the sound generation, enormous values which are incapable of being 65 measured even with the apparatus available at the present time. 70 dependent on the distance, measured in milli metres,,of a source of sound with constant sound energy from the microphone. The broken line 0-0‘. indicates the intensity of an interfering noise in the same room, this intensity remaining the same at the point of the effective surface 16 - - The steep ascent of the curve a-b in the case of small spacial disposal provides a certain indication of the un- ' usual extent to which the potential delivered by the microphone will rise when the microphone is approached even more towards the sound source, 1. e., is moved immediately up to the latter. It will accordingly be obvious from the above that the approach of the effective surface of the microphone of good, i. e., straightfrequency char acteristic employed according to the invention immediately up to the mouth of the person speaking is of decisive importance. Since the ratio between voice energy and interfering energy at the effective surface of a microphone situated immediately against the source of sound is ex ceptionally favorable. particular precautions do not require to be taken to withhold the interfer ing noise from the microphone. Practical ex periments have shown that with the apparatus according to the invention proper and faultless intelligibility is capable of being obtained even if the unprotected ear is acted upon even to the extent of a sensation of pain. . It has also been found thatv particular ad vantage is obtained if the current of air pro duced upon speaking is not allowed to impinge vertically on the surface of the microphone situ ated immediately in front of the mouth and thus exert a detrimental effect on the vibrations. According to the invention, therefore, the effec tive surface of the microphone arranged in the immediate vicinity of the source of sound is dis posed approximately parallel to the direction of speech, 1. e., to the direction of movement of the current of air formed upon speaking. With this arrangement the current of air is more or less able to sweep past the surface of the microphone, so that it is then unable appreciably to distort The invention will be described more fully with reference to the accompanying drawing, in the alternating potentials delivered by the micro phone. Preferably the holding member for the which on the distance of the latter from the source of microphone is so constructed that the effective surface of the microphone when the receiver is 70 placed against the ear is situated at the corner of the mouth. sound. Fig. 2 is a perspective view showing the tele microphone surface 2, which is located in a pro ‘ Fig. 1 is a diagram showing the alternating potential delivered by a microphone dependent 75 phone according to the invention in actual use. As shown, for, example, by Fig. 2, the effective tective casing I,‘is situated, when the holding 3 9,121,941 ' member 3 with the receiver 4 is lifted to the ear,~ ' at the corner of the mouth'of-the user and’in a ' ,very' close ‘to the comer of the mouth of the plane parallel to the breath currents of the user. ' ‘speaker. The microphone, therefore, as shown . in Fig. 4, is not furnished with the usual trumpet like or similarly shaped mouthpiece. vAs stated above, there is‘ employed a. microphone with good, 5. In a telephone transmitting and receiving set, a non-mouthpiece microphone casing and a microphone free of chattering e?z‘ect and having a‘ practically straight-line frequency character istic in the audible range, the said microphone being mounted forwardly in the said casing, and In the forms ‘of embodiment, shown in the the construction and arrangement being ‘such that the. effective surface of the microphone is 10 drawing the holding member 3 has af?xed there movably disposed in the immediate vicinity of ‘ torboth the transmitter l, 2 as well as they re ceiver 4. Naturally, as» regards the invention, the speaker's mouth to positions substantially ' it'is quite immaterial whether the ‘microphone parallel to, the direction of speech‘when the tele i. e., approximately straight frequency‘ charac teristic not revealing a chattering effect. and the receiver are united in one holder, or whether the holder,- which may be placed for ex phone-is in use. - Y 6._In a telephone transmitting and receiving 15 set, a non-mouthpiece. microphone casing‘, a ample about the head,.carries merely. the trans mitter I, 2. The essential feature is that the microphone free of chattering eifect‘and having a surface of the microphone 2 is situated in the ' practically straight-line frequency characteristic in the audible range, the said microphone being immediate vicinity of the source of sound. mounted with its effective surface forwardly in V20 To be able to adapt the requisite small spac 20 the said casing substantially parallel to the direc ing of ' the effective microphone surface accord ing to the invention to diiferentsizes of head the tion of speech when the telephone is in use, and transmitter is secured ‘to the holding member ‘ means for moving the effective surface of the said 3 so as to. be adiustable in the plane of the microphone while maintaining the eifective sur-, face thereof in the same plane to a position in the microphone surface 2. ‘ I _ In the form of embodiment according to Figs. _ immediate vicinity of the speaker's mouth irre 2 to 4 this adjustability is obtained by an arm - spective of the size of the head of the speaker. ‘L'A sound'transmitting device for telephone 5, which is eccentric and mounted to be rotatable in a corresponding abutment 8 on the holding systems intended for use more particularly under ‘so member. In this way it ‘is a simple matter to noisy conditions, comprising a microphone, free 30 adjust the transmitter in such fashion in relation from chattering effect and having a practically straight frequency-characteristic, devoid of res to the holding member in the plane of the micro phone surface as to ensure the necessary mini-v onance in the audible range, said microphone be mum spacing of the microphone surface from the ing adjustably mounted in a telephone set, so that when the receiver is applied to the ear, the source of sound. In the form of embodiment ‘according to Figs. effective surface of the said microphone may be 5 and6the casing I of the'transmitter is mounted tolbe oscillatory on the holding member 1 by be situated in the immediate vicinity of the means of an‘arm 1; speaker’s mouth at one of the'corners thereof. ' ‘ I ‘ It will be understood that the invention is not limited to the speci?c details of construc tion illustrated in the drawing, and that nu merous modifications ‘are quite possible within .40 the meaning of the above description and the 45 annexed claims without departing from the spirit of the invention. What I claim as new and desire to secure by 1. A telephone transmitting and receiving set comprising a rigid holder, a receiver mounted at one end thereof and an abutment carried by the other end of said holder, a microphone cas ‘ing having an arm eccentrically ?xedl'thereto, said arm being rotatable on said abutment, and a microphone of relatively low sensitivity mounted in said casing. f 2. The device as claimed in claim 1, in which the plane of the effective surface of ‘the micro phone is always parallel to the effective surface of the receiver. " , ' ‘ 3. The device as claimed in claim 1, wherein > the ‘microphone casing arm extends angularly ' from the casing. 8. A sound-‘transmitting device according to ' claim 7, in which the effective microphone sur face arranged in the immediate vicinity of ‘the source of speech is located‘ in a plane, which is directed parallel 'or approximately parallel to the direction of movement of the current of air resulting upon the formation of the spoken sounds. - ‘ 9. A receiving ‘and transmitting set for tele Letters Patent is: 65 moved in a plane of the surface thereof so as to , 4. A telephone transmitting and receiving set comprising a holder, a sound receiving apparatus mounted in said holder, a microphone free of chattering effect and having a practically ' straight frequency characteristic which is devoid _-of resonance in the audible range, adjustably mounted at the other end of the holder, the con struction and arrangement being such that when L70, the sound. receiving apparatus is held to the ear. the e?ective surface of the microphone may lie phones, intended for use more particularly under noisy conditions, comprising a stock, a receiver mounted therein, an arm mounted in said stock, a microphone free from chattering effect and ' having a practically straight frequency character istic, devoid of resonance in the audible range, mounted in said arm the axis of said microphone being eccentric to the arm's axis of rotation and V the plane of the'surface of said microphone par allel to the face of the said receiver. 10. A telephone transmitting and receiving set, comprising a holder,.a sound receiving apparatus ‘ mounted in said holder, 9. non-mouthpiece micro phone casing mounted on the holder, a micro phone free of chattering effect and having a prac tically straight frequency characteristic which is devoid of resonance in the audible range mounted 65 forwardly in the said casing, the construction and arrangement being such that when the sound re ceiving apparatus is held to the ear the effective surface of the microphone may be moved to lie at the corner of the mouth of the user and in a 70 plane parallel to the breath currents of the user. GiiN'rrmR. 'WURDEL.