Патент USA US2405858код для вставки
Aug. 13, 1946. 2,405,858 H. c. SILENT ACOUSTIC COUPLER FOR CONDENSER MICROPHONES Filed Nov. 29, 1944 mm .q ~7 \ _ I: . , : v: A\N \% E N m1.,. \ \N. 9o_3 .\IN0 \ N. .5::..am 9ON 2,405,858 Patented Aug.,13, 1946 UNITED STATES PATENT OFFICE 2,405,858 ACOUSTIC COUPLER FOB, CONDENSER MCROPHONES Harold 0. Silent, Los Angeles, Calif., assignor to the Government of the United States of America, as represented by the Secretary of the Navy Application November 29, 1944, Serial No. 565,757 6 Claims. (Cl. 181-05) 1 This invention relates to an acoustic coupler for transmitting sound waves to a condenser microphone while excluding moisture and dust 2 serves to clamp the ring ‘I and thin rubber dia phragm 8 against the ?ange 3. The diaphragm 8 is of such thickness and elasticity as to trans particles from the microphone assembly. mit sound without substantial attenuation of It is an object of this invention to provide means for efficiently transmitting sound waves to the sound energy. Fixed on one end of member 2 is the element 9 which has a. cylindrical portion I0 that ?ts snugly upon the shoulder 4 and is also provided with a microphones and which will prevent impairment of the functioning of the microphone due to ac~ cess of dust or moisture when used under ?eld shoulder H to bind the gasket l2 tightly against 10 ?ange 6. Cooperating with the member 0 to form conditions. an enclosed annular chamber is the sleeve !0 that A further object is to provide such a device with means to control, to a limited extent, the frequency response of the device. The single ?gure of the drawing shows in en larged longitudinal section a satisfactory embodi ment of my invention. It is well known that microphones are used in military operations to pick up the sounds of gun ?re and thereby to determine the distance and covers the joint between members 2 and 5. The chamber so formed is ?lled with a hygroscopic, or desiccant granular material I 3 which is re~ tained by ?brous or ?lamentary material [4 and a ?ne Wire screen It? from passing into the breath or ducts l6 and [1. An opening 26, stopped by a closure 21, is provided for observing when the desiccant l3 should be replenished or renewed. Secured to the member 9 at one end and to the location of such guns and, to a certain extent, 20 end element l8 at the other, surrounding mem the caliber of the guns. ber 2 and spaced therefrom, is a highly ?exible The most frequent equipment failure encoun rubber bellows I9. This bellows is held in air tered with such instruments when the micro tight relation to the members 9 and I8 by tightly phone is of the condenser type is in the con denser element, wherein the small space between 25 drawn threads 20 disposed over the bellows I!) in grooves. Bellows I9 is protected externally by a the stator plate and the diaphragm is exposed sleeve 2| which may be of any suitable material' to an outer chamber through a ?lter plug pierced such as one of the well known synthetic plastics with several small holes, and the outer chamber provided with an opening through which atmos is in turn open to the atmosphere through a pheric pressure may act upon bellows l3. The similar plug. These passages offer no barrier to construction just described con?nes a body of the entrance of dust particles and moisture laden air within the tubular assembly back of the dia air into the condenser element as a result of tem phragm B and inside the bellows IS. The pres, perature and barometric pressure changes. sure on the opposite sides of diaphragm 8 is thus The entrance of moisture not only reduces the equalized by movement of air between the space necessarily high resistance of the condenser, re enclosed by bellows l9 and member 2, and the sulting in loss of sensitivity, but causes the ele space in the member 2 by way of the ducts l5 ment to become erratic or noisy. The presence and I‘! and through the desiccant material I3 of even exceedingly small quantities of dust in and thus any moisture in the air so con?ned is the condenser chamber which usually is a space of only 0.006 inch will cause noisy and erratic 40 removed as it passes through the desiccant ma terial l3 in response to variations of atmospheric operation of the instrument. The reconditioning pressure. of a microphone under ?eld conditions is ex The end element I8 is provided with external tremely di?ioult to accomplish. Accordingly, the threads 22 for connecting the coupler to the coupler constituting the present invention has been devised to protect the microphone against 45 microphone housing in place of the ?lter plugs above mentioned. The passages 23 through the the entry of dust and moisture. end element 18 permit transmission of sound Referring now to the drawing, it will be noted waves to the microphone mechanism. A removthat the coupler comprises in general a tubular able screw 24 is disposed in the end element l8 assembly constituted by the major portions I and 2. Fixed to one end of the member I, as by 60 and may be taken out when it is desired that the upper limit of the frequency response of the de sweating or brazing, is a ?ange 3 having formed vice should be raised. For example, with the thereon a shoulder 4. Secured to the flange 3 is screw 24 in place the upper limit of response may an element having a tubular portion 5 of the be 60 cycles per second but when it is removed same radial dimensions as members I and 2 and also having a radially extending ?ange 6 that 55 that upper limit will be 100 cycles per second. I 2,405,858 3 The end of the assembly remote from the mi crophone is preferably provided with a wire screen 25 to prevent entry of any large particles of dirt or other matter that might damage, or interfere with the sound response of, diaphragm ii. I claim: 1. An acoustic coupler for a condenser micro phone having a single restricted opening for ac cess of sound Waves thereto, comprising a ?rst tub lar part having an internal shoulder adja 10 cen, one end, a second tubular part having one of its ends secured in the said one end of the ?rst part, a thin rubber diaphragm clamped in position between said shoulder and the said one end of the second part to close the opening through the parts against moisture and dirt, means de?ning a closed annular chamber around a portion of said ?rst part, a body of granular disiccant in said chamber, a flexible member surrounding the major portion of said ?rst part secured at its ends to said ?rst part in air-tight relation and spaced therefrom between its ends, there being ducts connecting said annular cham ber to the space within said member and other ducts connecting said chamber to the space within said ?rst part, matter ?lamentary mate- of its ends secured in the said one end of the ?rst part, a thin rubber diaphragm clamped in position between said shoulder and the said one end of the second part to close the opening through the parts against moisture and dirt, breather means including a ?exible member re sponsive to changes in air pressure disposed in air-tight relation around the ?rst part and spaced therefrom to enclose a body of air, a con ?ned body of desiccant material, and ducts to permit passage of air between said body of air and the interior of the ?rst part through the desiccant material. 4. An acoustic coupler for a condenser micro phone having a single restricted opening for ac cess of sound. waves thereto, comprising a ?rst tubular part having an internal shoulder adja cent one end, a second tubular part having one of its ends secured in the said one end of the ?rst part, a thin rubber diaphragm clamped in position between said shoulder and the said one end of the second part to close the opening through the parts against moisture and dirt, means to equalize air pressure on opposite sides of the diaphragm including a member cooper ating with the ?rst part to de?ne an enclosed space having a volume that is variable with changes in air pressure, passages to permit movement of air between said space and the in 30 terior of the ?rst part, and an enclosed body of rial disposed to exclude the disiccant from said ducts, and an end member ?xed to and substan tially closing the other end of the ?rst part, said member being provided with elements to secure the coupler to the microphone to conduct sound hygroscopic material disposed in the path of air to said opening in the microphone and with pas moving between the interior of the ?rst part and sages for the transmission of the sound, and a said space. removable closure in one of said passages which, 5. An acoustic coupler for a condenser micro when the closure is removed, renders the device 35 phone having a single restricted opening for ac effectively responsive to higher sound frequen cess of sound waves thereto, comprising a tubu cies than when the closure is in the passage. lar assembly, a thin rubber diaphragm across the 2. An acoustic coupler for a condenser micro interior thereof intermediate its ends, a member phone having a single restricted opening for ac ?xed to one end of the‘ assembly to attach the cess of sound waves thereto, comprising a, ?rst 40 assembly to the microphone in operative relation tubular part having internal shoulder adja to said opening, said member having passages for cent one end, a second tubular part having one transmission of sound waves to the microphone, of its ends secured in the said one end of the ?rst means associated with a said passage to vary the part, a thin rubber diaphragm clamped in posi sound frequency response, means to enclose a tion. between said shoulder and the said one end volume of air Variable in response to changes in ' of the second part to close the opening through the ambient air pressure connected to the space the parts against moisture and dirt, means de between the diaphragm and the said member, ?ning closed annular chamber around a por and material to remove moisture from air pass tion of said ?rst part, a body of granular desic ing between said space and said volume of air. ant in said chamber, a ?exible member sur 6. An acoustic coupler for a condenser micro rounding the major portion of said ?rst part se phone having a single restricted opening for ac ured at its ends to said ?rst part in air-tight re cess of sound waves thereto, comprising a tubu ation and spaced therefrom between its ends, lar assembly, a moisture and dust excluding di there being ducts connecting said annular cham aphragm across the interior thereof intermedi ber to the space within said member and other ate its ends, said diaphragm transmitting sound ducts connecting said chamber to the space with waves without substantial attenuation of‘ the in said ?rst part, matter ?lamentary material sound, a member ?xed to one end of the assem disposed to exclude the desiccant from said ducts, bly to attach the assembly to the microphone in and an end member ?xed to and substantially operative relation to said opening, said member closing the other end of the ?rst part, said mem 60 having passages for the transmission of sound her being provided with elements to secure the waves to the microphone, means associated with coupler to the microphone to conduct sound to a said passage to vary the sound frequency re said opening in the microphone and with pas sponse, means to enclose a volume of air in re sages for the transmission of the sound. sponse to changes in the ambient air pressure 3. An acoustic coupler for a condenser micro connected to the space between the diaphragm phone having a single restricted opening for ac and the said member, and material to remove cess of sound waves thereto, comprising a ?rst moisture from air passing between said space tubular part having an internal shoulder adja and the said volume of air. cent one end, a second tubular part having one HAROLD C. SILENT.