US2342334A - Variable baffle for translating devices - Google Patents

Description

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1M 2 o M l m I T l J HIM 1 am A y a F H J m fl d F e VARIAB-LJE BAFFLE FOR TRANSLATING DEVICES Fails. 22, 1944.

Patented Feb. 22, 1944 "UNITED T OFFICE 2,342,334 'vlfitrdnm 'B'AFTifLE FOR TRANSLATING DEVICES Fl ank J. Faltico,-Minneapolis, Minn, assigno'r to The Maico Company Incorporated, Minneapolis, Minn., acorporation of Minnesota Application July 11, 1942, Serial No. 450,600

8'Claims. This invention relates generally to improvements in translating devices, such as headphones, and more 'particularly to means for adiusting the baffle efiectin such devices'to thereby secure variations in frequency response.

The primary object of the'invention is to proivide means whereby'the baffle effect of theusual headphone may be easily an quickly varied by permitting the passage of airwaves between the front or outer side of the diaphragm and the back or inner side thereof. ZBy this means the usualinfinite baffle of such devices may be altered according to requirements and the frequency response varied by permitting at least the partial 1 cancellation of unwanted frequencies in the audio range. Another object is to provide means of this nature in any extremely simple and practical'formembodying simply an air passage-way communicating with the opposite sides of the diaphragm and a member arranged to adjustably open or close said passage-way and thereby control the volume of air passing therethrough.

These and other more detailed and specific objects will be disclosed in the course of the following specification, referenc being had to the accompanying drawing, in which- Fig. 1 is a diametricalsection through aheadphone type of translating device showing my invention embodied therein. A

Fig. 2 is an inside elevation or plan view of the cap forming part of the structure of Fig. 1, showing the adjusting screw removed.

Fig. 3 is an enlarged, fragmentary cross sectional view illustrating the communication between opposite sides'of the diaphragm.

Fig. 4 is a face or plan view-of the body or case'member forming part of the headphone, a portion thereof being shown in section.

Referring now more'particula'rly and by reference characters to the drawing, a headphone type of translator or receiv'er'is shown embodying essentially a casing or body member A having an annular shell B against the'end of which the vibrating diaphragm 'Cis placed and held by 'a cap'D, said cap being's c'rewed onto the body member as indicated at E (or otherwise fastened) and 'having'a central opening F for the p'a'ssageof sound waves formed byvibrati'on of the diaphragm. An electromagnetic "vibrating or driving motor or device G is secured to the body member 'A as clearly shown and includes wire wound pole pieces H disposed adjacent the diaphragm C.

The foregoing constitutes the usual construction of such units and no invention is herein claimed for such construction 'per se. In operation, the diaphragm 'C isvibrated'by the mechanism G in accordance 'With the variations in electrical current flowing therein, and such vibrations cause the formation of sound waves in the air which are emitted from the diaphragm and are audible to the ear. Obviously only 'the sound Waves formed by the outer, or 'as usually termed, front side C of the diaphragm will be audible and the waves formed by the inner, or properly, rear side or back '0" of the diaphragm will be confined to the cavity formed between body member A and cap D. Accordingly there will be no cancellation of certain frequencies by the movement of out of phase sound waves from front to back of the diaphragm, as occurs where there is means of communication between opposite-sides, and the frequency response is there- 'fore substantially fiat or level throughout its range. The effect isas though there were a baffle of infinite size such that no frequencies could possibly reach the back of the diaphragm in :proper phase relation to cause cancellation.

Such fiat frequency response is a disadvantage under some circumstances such as Where the unit is used primarily for voice and communication work, or particularly where the unit is a part of a hearing aid device for use by the hard of hearing. 'In such cases it is very desirable to vary the frequency response to effectively accentuate desired frequencies by the reduction or cancellation of unwanted or useless frequencies. For example, most persons having diificulty in hearing have better perception at certai'n frequencies than at others, and the'adjustment of the response of the unit to-givemaXimum effect to the frequencies at which hearingloss is greater is obviously desirable. In accordance with my invention, therefore, I provide means for varying the ba'fiie eiTect of the casing'andcap upon the diaphragm C as will'now be described.

The cap D is formed with a'shoulder or ledge I0 adapted to bear against the margin of the diaphragm and press it against the end of the shell B, and'to thus provide space I I for vibratory movement of the diaphragm. I provide, then, a channel or groove l2 in this ledge at one point (or more) extending radially therein -and communicating with the space H at the front of "the diaphragm. This channel also communicates with a similar (or continuation) channel or groove [3 formed in the interior annular surface M of the cap D which contacts the corresponding annular outer surface id of the shell 33. In this shell there is formed a radially extending opening It which registers at its outer end with the channel [3 and at its inner end communicates with the cavity back or at the rear of the diaphragm. At a point radially aligned with the opening it the cap D has in its flange or outer wall IT a tapped opening or socket l8 opening into the channel It and in which is placed a threaded plug or screw E9. The screw may obviously be moved inward or outward in the opening l8 by a screw driver inserted through the open outer end thereof. The screw or plug I9 is preferably larger in di-' ameter than the opening It or the width of channel 13 so that they may be completely closed oif when the plug is screwed inward as seen in Fig. 1.

Essentially, then, the invention is seen to comprise an air passage, channel or vent, made up by the channels |2I3 and the opening it, communicating at its ends with the opposite front and rear sides of the diaphragm C, and with means, formed here by the plug or screw Iii, to open or close this passage and vary the effective capacity thereof. It is evident that when the plug I9 is screwed inward as far as possible the communication between front and rear of the diaphragm is entirely out off and the baffle effect is infinite. As the plug is drawn outwardly the passage-way is gradually opened permitting the flow of air from front to back of the diaphragm in greater or lesser volume or degree as indicated in Fig. 3, to thus gradually reduce the baffle efiect and accordingly vary the effective frequency response of the unit. Such adjustment may be readily carried out to any degree required and, since the plug H) is carried wholly by the cap D, the removal of this cap for any reason will not affect the adjustment, once it is made.

It is understood that suitable modifications may be made in the structure as disclosed, provided such modifications come within the spirit and scope of the appended claims. Having now therefore fully illustrated and described my invention, what I claim to be new and desire to protect by Letters Patent is:

1. In a device of the character described, a

vibratory diaphragm, a casing supporting the said diaphragm and having a portion enclosing one side of the diaphragm and isolating that side from the opposite side and thereby causing an infinite baffle effect, said casing having a passage-way connecting the opposite sides of the diaphragm, and means associated with the casing for opening and closing the said passageway to control the flow of air from one side of the diaphragm to the other.

2. In a headphone of the character described, a casing, a diaphragm marginally supported in the casing and having its front side exposed but having its rear side enclosed by said casing, an air passage means formed in the casing and communicating at its respective ends with the front and rear sides of the diaphragm, and means for varying the efiective size of the said air passage means to thereby vary the bafile effect of'the casing upon sound waves emitted by the diaphragm.

3. In a headphone of the character described, a casing comprisinga body member and a cap member removably mounted thereon, a dia phragm supported by the casing in such manner as to be exposed at its front side and enclosed at its rear side, and air passage means for permitting the limited passage of air between front and rear sides of the diaphragm, the said air passage means being formed in part in the body member and in part in the cap member.

4. In a headphone of the character described, a casing comprising a body member and a cap member removably mounted thereon, a diaphragm supported by the casing in such manner as to be exposed at its front side and enclosed by the casing at its rear side, and air passage means for permitting the limited passage of air between front and rear sides of the diaphragm, the said air passage means being formed in part in the body member and in part in the cap member, and means carried by the cap member and operative to enter the air passage means to vary the efiective size thereof.

5. In a headphone of the character described, a casing comprising a body member and a cap member removably mounted thereon, a diaphragm supported by the casing and enclosed at its rear side by said casing, the said cap member having an opening to partially expose the front side of the diaphragm, and the said body member and cap member having respectively an opening and a channel forming a means for conducting air between front and rear sides of the diaphragm.

6. In a headphone of the character described, a casing comprising a body member and a cap member removably mounted thereon, a diaphragm supported by the casing and enclosed at its rear side by said casing, the said cap memher having an opening to partially expose the front side of the diaphragm, the said body member having an opening communicating with the rear side of the diaphragm, and the said cap member having a channel communicating with the front side of the diaphragm and adapted also to communicate with the said opening when the cap member is mounted upon the body member.

7. In a headphone of the character described, a casing comprising a body member and a cap member removably mounted. thereon, a diaphragm supported by the casing and enclosed at its rear side by said casing, the said cap member having an opening to partially expose the front side of the diaphragm, the said body member having an opening communicating with the rear side of the diaphragm, the said cap member having a channel communicating at its respective ends with the said opening and with the front side of the diaphragm, and a plug threaded in the cap member and operative to adjustably open and close the said channel.

8. In a headphone of the character described, a casing including a body member having a re.- cess in one side, a diaphragm mounted at one sidev over the recess and adapted when vibrated to transmit sound wave vibrations from both its sides, a cap member mounted over the other side of the diaphragm, and means in the body member and cap member providing communication for the passage of sound waves between the opposite sides of the diaphragm.

FRANK J. FALTICO.

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