|Publication number||US3246721 A|
|Publication date||Apr 19, 1966|
|Filing date||Apr 24, 1963|
|Priority date||Apr 27, 1962|
|Also published as||DE1188656B|
|Publication number||US 3246721 A, US 3246721A, US-A-3246721, US3246721 A, US3246721A|
|Original Assignee||Siemens Ag|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (8), Referenced by (12), Classifications (5)|
|External Links: USPTO, USPTO Assignment, Espacenet|
April 19, 1966 E. MARTIN 3,246,721
FREQUENCY RESPONSE OF AN ELECTRO-ACOUSTIC TRANSDUCER Filed April 24, 1963 2 Sheets-Sheet 1 s lain Fig.2 L0 R0 co L'3 R'3 ll IF I L'1 R! LI Fig.4
3 yxnxxxxxg IIQQR'OC R C3 R3 L 2; c1. LORO co April 19, 1966 E. MARTIN 3,
FREQUENCY RESPONSE 0F AN ELECTRo-ACOUSTIC TRANSDUCER Filed April 24, 1963 2 Sheets-Sheet 2 .as a coupling to the other resonator space.
United States Patent S 6 Claims. (Cl. 18131) The invention disclosed herein is concerned with an arrangement for improving the frequency response of an electro-acoustic transducer. The transducer according to the invention comprises a housing which is, with the aid of a membrane and a partition wall, which wall is provided with at least one break-through, subdivided to'form a space respectively in front and in back of the membrane and also a resonator space.
"It has been customary for many years to provide, in electro-acoustic transducers, resonator-s for the purpose of improving the frequency response. There are absorption resonators known which absorb a resonance'peak of the frequency response and also resonators which are operative to raise the frequency response in the lower part of the transmission range. Such resonators are coupled either to the space in front or the space in back of the membrane.
The present invention introduces, for an electro-acoustic transducer of the initially indicated kind, a particularly advantageous arrangement for an auxiliary resonator space. This arrangement, as compared with prior resonator arrangements, permits with simple measures a coupling to the frontal space of the membrane as well It is also possible to effect simultaneous coupling to the two indicated spaces, thereby producing a particularly favorable action with respect to the frequency response.
The characteristic feature of the invention resides in the provision of a further cylindrical partition wall, be-
tween the first partition wall and the membrane, so as to form an auxiliary annular resonator space which is sealed with respect to the rearward space of the membrane.
The foregoing and further objects and features of the invention will appear from the description of embodiments which is rendered below with reference to the accompanying drawings.
FIG. 1 shows the principles applied in an arrangement according to the invention, with the auxiliary resonator space provided with an opening to the frontal space of the membrane;
FIG. 2 represents the electrical analog or equivalence circuit for the arrangement according to FIG. 1;
FIG. 3 indicates a constructive realization in connection with an electromagnetic transducer;
FIGS. 4 and 6 illustrate examples of the arrangement according to the invention, wherein openings are provided leading from the auxiliary resonator space to the original resonator space which is coupled to the rearward space of the membrane, and with openings to the latter resonator space and the frontal space of the membrane; and
FIGS. 5 and 7 represent electrical analog or equivalence circuits respectively for the embodiments illustrated in FIGS. 4 and 6.
Accordingly, FIGS. 1, 3, 4 and 6 show the spatial arrangement of parts and FIGS. 2, 5 and 7 show electrical equivalence circuits drawn in accordance with the force-voltage analogy.
FIG. 1 shows an electro-acoustic transducer having a housing G which is disposed within the chamber HA of a telephone hand set. The transducer housing G is by the membrane M and the partition wall T1, which ture principle. shown (in FIG. 3) so as to give a practical example for the applicability of the arrangement illustrated in is provided with a break-through L1, subdivided to form the frontal space C4 and the rearward space C2 of the membrane, and also the resonator space C1. The breakthrough L1 in the partition wall T1 is closed by an acoustic resistor R1.
The sound passage openings of the transducer housing are contiguous to the sound passage channels L3, R3 which extend to the outside. It is in the present case assumed that the electro-acoustic transducer is also used as a receiver. There is therefore indicated an aural volume C3. According to the invention, there is provided, by a further cylindrical partition wall T2 extending between the first partition wall T1 and the membrane M, an auxiliary resonance space C5 which is sealed with respect to the rearward space of the membrane. This auxiliary resonance space C5 is in this embodiment connected with the frontal space of the membrane over the annular acoustically operative channel L6, R6.
FIG. 2 represents the electrical analog or equivalence circuit corresponding to the acoustic conditions of FIG. 1. The capacitances correspond to the reciprocal stilfnesses of the respective volumes and the inductances and resistances correspond respectively to the masses and the acoustic resistances of the respective openings. The elements indicated by the sign refer to the membrane. The branch R'6, L6, C'5, corresponding to the solution according to the invention, which distinguishes over the known networks, by the parts indicated by prominent lines.
If the volume of the auxiliary resonator space C5 is relatively great, the capacitance of the capacitor C5 will likewise be relatively high. It acts in a manner similar to a shunt, so that the series circuit of the inductance L6 and the resistance R'6 lies parallel to the capacitance C4, making it possible, with appropriate dimensioning of the inductivity and the resistance, that is, with appropriate dimensioning of the acoustically active opening at the rim of the membrane, to effect a raising in the lower part of the frequency band.
If the volume of the auxiliary resonator space C5 is relatively small, there may be obtained, by appropriate dimensioning of the opening L6, R6 (FIG. 1), at the rim of the membrane, a resonator which is tuned to a frequency in the central or upper part of the transmission range. This resonator acts in such case as an absorption resonator and can be used for the attenuation of a resonance peak in the frequency response of the transducer.
The arrangement of the auxliary resonator space is particularly important in connection with electromagnetic transducers operating in accordance with the ring arma- Such a transducer is therefore likewise FIG. 1. The annular support A for the ring shaped armature RA is dimensioned and arranged so as to leave an intermediate space between the permanent magnet D and the support A, such space being utilized as auxiliary resonator space C5. The acoustically effective connection with the frontal space of the membrane is established by one or more cutouts L6, R6, formed at the outer rim of the membrane.
The structure according to FIG. 4, in which the auxiliary resonator space C5 is not connected with the frontal space C4 of the membrane but, over an acoustically effective opening L7, R7, with the resonator space C1 in back of the membrane, produces an effect which will now be described with reference to FIG. 5.
With appropriate translation and size of the auxiliary resonator space C5, C5 in FIG. 5 can be neglected. The oscillation structure C2, L'l, C'l, L'7 can then be tuned to two resonance peaks within the transmission range. Upon tuning the weakly attenuated Helmholtzresonator L1, C1, to the membrane resonance (about 2000 cycles) and the auxiliary resonator to the lower resonance rise (about 1400 cycles) of the Helmholtzresonator, there will be obtained a linearized frequency course without requiring attenuation of the Helmholtzresonator with the aid of silk. The relatively slight attenuation due to the friction of air at the resonance neck is in such a case sufficient. This condition is indicated in FIG. by dash-line representation of the acoustic resistance R]. (R1 in FIGS. 1 and 4).
In the embodiment shown in principle in FIG. 6, there is provided, in addition to the acoustically effective connection L6, R6, between the auxiliary resonator space C5 and the space in front of the membrane, the further acoustically effective connection L7, R7, extending between the auxiliary resonator space C5 and the original resonator space C1. The operation obtained thereby may be explained with reference to the electrical analog circuit representation shown in FIG. 7.
In FIG. 7, the openings referred to, represented by the inductances L6 and L'7, as well as the resistances R6 and R7, and the volume of the auxiliary resonator space, represented by the capacitance (3'5, are shownin prominent lines. The analog circuit represents an approximation for cases in which (3'1 is considerably greater than C4 and wherein the two openings in the auxiliary resonator have about the same cross-sectional area.
The case in which the volume of the auxiliary resonator space C5 is relatively small, is of interest. In such case, the leakage over the capacitance C'S can be neglected, so that the inductances U6 and L7 are in series relationship. They form, jointly with the capacitances U1 and C4, a parallel oscillation circuit which can easily be tuned to low frequencies even in the case of small mass of the resonator openings. due to serial relationship of the two inductances L6 and L7. Such tuning permits raising of the frequency response in the low part of the transmission range.
With appropriate size of the auxiliary resonator space C5, the measure indicated in FIG. 6 will not only permit tuning at low frequencies and therewith raising the frequency course in the lower part of the transmission range, but will, with appropriate dimensioning of the opening L6, R6, effect an absorption at one resonance peak in the transmission range. In such case, the series resonance of the elements L'6, R6, C'S (FIG. 7) becomes effective.
Changes may be made within the scope and spirit of the appended claims which define what is believed to be new and desired to have protected by Letters Patent.
1. In an electro-acoustic transducer having a housing which is by a membrane and a partition wall, which wall is provided with at least one break-through, subdivided into'a space formed respectively in front of the membrane and in back thereof, an arrangement for improving the frequency response of the transducer, comprising a further, cylindrical, partition wall disposed between the first This is substantially 4 named partition wall and the membrane, said further partition wall forming an auxiliary annular resonator space which is sealed thereby with respect to the laterally adjacent space in back of the membrane.
2. An arrangement according to claim 1, wherein said auxiliary resonance space communicates with the space in front of the membrane by way of at least one acoustically effective opening formed at the rim of the membrane.
3. An arrangement according to claim 2, wherein the outer diameter of the membrane is somewhat smaller than the inner diameter of the housing at the level of the membrane, thus forming an annular gap between the named parts.
4. An arrangement according to claim 2, wherein the membrane is peripherally thereof at least in part perforated.
5. An arrangement according to claim 2, wherein the auxiliary resonator space communicates with a resonator space coupled to the space in back of the membrane, by Way of at least one acoustically effective opening.
6. In an electro-acoustic transducer, the combination of a housing including a front wall portion, a rear wall portion, and peripheral wall means connecting the front and rear wall portions, a membrane and a partition wall extending between the peripheral wall means and subdividing the housing interior to form a first space between said membrane and said front wall portion, and a second space between said membrane and said partition wall, the latter having an opening therein, and a further tubular partition wall extending between the first-mentioned partition wall and the membrane and cooperable therewith and with said peripheral wall means to define an annular resonator space with said tubular partition wall forming a seal between said resonator space and the laterally adjacent space between said membrane and the first-mentioned partition wall, said annular resona tor space having an opening in a wall defining the same, providing communication between such annular resonator space and an adjacent space Within said housing.
References Cited by the Examiner UNITED STATES PATENTS 1,854,716 4/1932 Pape 181--31 2,327,137 8/1943 Shapiro 179-107 2,342,334 2/1944 Faltico 181-31 2,490,466 12/ 1949 Olson et al 18131 2,524,393 10/1950 Lybarger 179-107 2,585,052 2/ 1952 Skelton.
2,778,882 1/1957 Pontzen et al 179--115.5
FOREIGN PATENTS 1,078,174 3/1960 Germany.
LEO SMILOW, Primary Examiner.
LEYLAND M. MARTIN, Examiner.
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|U.S. Classification||181/160, 381/337|