US2478783A - Telephone mouthpiece voice silencer with plural silencing chambers - Google Patents

Description

Aug. 9, 1949.

Filed June 17, 1946 L. TELEPHONE MOUTH S. SCHER PIECE VOICE SILENCER WITH PLURAL SILENGING CHAMBERS 2 Sheets-Sheet 1 INVENTOR. L OU/S 5. SCHEE.

ATTORNEY.

Aug 9, 1949. L. s. SCHER 2,473,733

TELEPHONE MOUTHPIECE VOICE SILENCER WITH PLUR'AL SILENCING CHAMBERS Filed June 1'7, 1946 2 Sheets-Sheet 2 INVENTOR. LOU/5 5. SCHER.

M A TT'ORNE Y Patented Aug. 9, 1949 umrso PATENT OFFICE TELEPHGNE MOUTHPIECE VOICE SILENCER WITHPLUR'AL'SILENCING CHAMBERS Louis. S. Scher, New York, N. Y. Application June17, 1946, Serial N'0."677,389

fiClaims. (Cl. 181-434) The present invention relates to "an'atta'chmerit for telephones'by meanscf which the voiceof the speaker'can be "substantially completely mines 'to ensure privacy in the presence of others.

Voice silencers fortelephones are-wel-l known. These essentially comprise a chamber lined or provided with sound-deadening"material such as felt, to provide acoustic absorption. While these devices are reasonably satisfactory and give a substantial amount 'ofprivacy to telephone conversations, they do have recognized disadvantages which have not, so far, been overcome. One such disadvantage residesin the fact'thatthe voice ofthespeakeris unclear to the listener at the otherend of the line. 'This'is partly due to interference caused by out-of-phase reverberation or fixed low-pitchedresonance-and partly the result of the buildin up of back-pressure where incorrect ventingor lack 'ofventing-exists. Although such back-pressureis slight it has an extr'emelyadverse efiectprobabl'y due to air pressure on thetransmitter diaphragm, besides low pitched resonance increasing undesirable tonal qualities. Whatever the precise cause or explanation, priorvoice mu-filersfor telephones have not been entirely satisfactory either from'anacousticalor from a mechanical or constructional point of view.

It is, consequently, anobject of this invention to-overcome the deficiencies-of prior telephone voice mufilersand to provide anew and improved device which is correctly designed acoustically and which is mechanically and structurallyperfected, as for instance, shaping the mufiler to conform. to the. telephone stand as well asrthe mouth of the user, without-any mechanical interference; the voice mufiler being soshaped, it will not interfere with normal lifting and hang in up of the telephone handset.

'Anotherobject of the invention is to provide a telephone voice mutter-Which ensures privacy without need of reducing the volume excessively for the listener at the other end oi the line, and Without appreciable loss of fidelitycf tone.

A further object of the invention is to construct a telephone voice muffler in which backpressure or sound distortion cannot be built up during even forcefulnseand in which correct and adequate ventingis provided for et the same time 'setting the natural pitch of the voice muffler considerably higher than would 'bethe case without venting.

'A still further object or the invention resides, in the useoi a relatively large massoi'sound-abexcessivesound absorption-and without adverse effectpn'the venting of the rnnfller as a whole.

Other objectsandadvantages lie in the various structuralcombinations and details hereinaftendeseribed.

In the accompanying drawings:

Fig. 1 illustrates my new telephone voice muffler as applied to a moderntelephone.

Fig. 2 is an el-evational View of the mufiler per-'se.

-Fig. 3--i-s aplan view of Fig. 2.

Fig.4 is-a bottom view of Fig. 2.

Fig. 5 is a view-looking from right to left of Fig. 2.

Fig. '6 is a view-looking from left to right of Fig. 2.

Fig. 7 is an enlarged sectional view of my new mu'fller showing inbroken lines a portion of the associated telephone.

Fig. 8 is a detail view of the exhaust box used in the form of muffler shown in Fig. 7.

Fig. 9. is aviewsimilar to Fig. 7, of asomewhat modified construction of mufiler.

new voice mufller. is essentially comprised of atelephonetransmitter engaging portion ill. and a. mouthpiece portion ll, each of which is composed of a. suitable plastic material of rigi non-deformable nature. Bakelite, acetate and other .materials. of similar types or rigid waxed paperioricastlightweight metal. are eminently satisfactory for thisipurpose.

. Portion. H1 is. of generally annular form-and is provided witha plurality .of equispaced springs [2,usua1lythreein number, which engage and hold the. muffler. in'place on the. telephone transmittenT, the :outer edge of which is received within the annulus of portion 10, as best shown in '7 of the drawings. Portion lo has'an. upstanding portion l3.of the inverted U-shaped crossesection whichextends. partially around the annulus ;of 2 portion Ill, somewhatv more. than ,a semi-circle. .rIn .plan, portion I3 is crescentshaped,.as. will be best appreciated from Fig. 3. Due to. theconstruction, just recited, it will be apparent that a crescent-shaped chamber-is formed within portion l3 and this chamber is substantially filled with sound-absofhg sound dea'dening material I4 which is not the conventionally employed felt. I have found that artificial or synthetic sponge constitutes aunique and highly efilcaciousmaterial and that it is light and resilient, properties rendering it highly suitable 'for thenipresent .purpose. .:It is, moreover, characterized by numerous :small passages forming a veritable network into which sound waves can penetrate and be absorbed. This material can be removed and rinsed in water or sterilized and used over again when dried. It does not have the massiveness or weight of felt and, therefore, results in more satisfactory sound absorption which renders the voice more intelligible to the listener at the other end of the line. It does, however, efiectively mufile the voice of the speaker to those within normal hearing range. An arouate perforated shield it, preierably fabricated from a light metal such as aluminum, is disposed between the inner surface or material I4 and the inner Wall of portion I3,

It will be noted that material Hi does not completely fill the crescent-shaped chamber formed by th combined transmitter-engaging portion and mouthpiece portion and that the lower edge of shield I5 extends below the material It. This arrangement forms a chamber ZI within mouthpiece portion I I. This chamber is in communication with the mouthpiece via the perforations in shield I5. The chamber is maintained against diminution in size or change of shape by means of an exhaust box lI forming a chamber I6 which is held in place by a suitable fastening instrumentality, such as the screw I8, th threaded end of which engages a nut I9 countersunk in the plastic body of the mouthpiece portion II, as shown.

It will be further noted that mouthpiece portion II is provided with a plurality of openings 20. These openings are located at critical points and constitute an important feature of the present invention; they not only provide an evenly distributed escapement for back pressure, but also raise the natural resonance pitch of the voice muffler as in an open flutepipe versus a closed pipe, a well-known fact in the science of sound. since exhaust box H is also provided with strategically located apertures, it will be understood that back-pressure escapement will pass through chamber It Without appreciable escapement of sound. All other escapement openings form long restricted passages in the thick sections of mouthpiece portion II, also create resistance to escapement of sound from the Voice mufiler.

In Fig. 9, the structure is substantially the same as that already described except that in some instances it has been found desirable to place the exhaust box IIa on the exterior of mouthpiece portion IIa, rather than in the interior as in Fig. 7. In this way, the chamber I6a is exterior and communicates with the reduced chamber 2Ia, within portion Ila. Back-pressure is avoided since through communication is provided via apertures Ila, openingsflfla, andthe perforated guard I5a.

The foregoing is presented as illustrative and not as limitative as other modifications may be resorted to without departing from the spirit or principles hereof. In particular, soft fabric inserts may be employed instead of springs I2 and Ila or any other suitable means may be provided for engaging and holding a telephone transmitter of any of the usual designs. The two main portions of the present mufller are readily assembled and disassembled and all members can be conveniently sterilized without damage thereto. 7

Having thus described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. A voice muffler comprising a telephon transmitter-engaging portion and a mouthpiece portion readily attachable to and detachable from each other, sound absorbing material of nonnbrous nature within said transmitter-engaging portion and means for preventing back-pressure in said mufiier during use, said telephone transmitter-engaging portion being of generally annular form and having an upstanding inverted U-shaped portion of crescent shape, the said sound-absorbing material being disposed within and completely filling the said upstanding portion and extending therebeyond into said mouthpiece portion, and a hollow exhaust box having openings communicating with the interior of said mouthpiece portion.

2. A voice mufller comprising a telephone transnutter-engaging portion and a mouthpiece portion readily attachable to and detachable from each other, sound absorbing material iOf nonfibrous nature within said transmitter-engaging portion and means for preventing back-pressure in said muflier during use, said telephone transnutter-engaging portion being of generally annular form and having an upstanding inverted U-shaped portion of crescent shape, the said sound-absorbing material being disposed within and completely filling the said upstanding portion and extending therebeyond into said mouthpiece portion, a hollow exhaust box having openings communicating with the interior of said mouthpiece portion, and a perforated shield along one side of said sound-absorbing material in the transmitter-engaging portion and extending into said mouthpiece portion.

3. A voice mufiler comprising a telephone transmitter-engaging portion and a mouthpiece portion readily attachable to and detachable from each other, sound absorbing material of non fibrous nature within and completely filling said transmitter-engaging portion and means for preventing back-pressure in said mufiler during use, said back-pressure preventing means including a series of openings through the mufiler wall communicating th interior of the muffler with the outer atmosphere, certain of which openings being laterally located to improve tonal qualities, and a hollow exhaust'box communicating with the mufiler to introduce a tortuous path for the relief of air pressure without impairing theefficiency of the sound-retaining qualities.

4. A voice mufiler comprising a telephone transmitter-engaging portion and a mouthpiece, portion, sound absorbing material within said transmitter-engaging portion and means for preventing back-pressure in said mufller during use, said telephonetransmitter-engaging portion being of generally. annular form and having an upstanding inverted U-shaped portion of crescent shape, the said sound-absorbing material being disposed within and completely filling the said upstanding portion and extending therebeyond into said mouthpiece portion, a hollow exhaust box on the wall of the mouthpiece portion, and having openings communicating the interior of said exhaust box with the interior of the mouthpiece portion and having other openings communicating the interior of the exhaust box with the outer atmosphere.

5. A voice mufller comprising a telephone transmitter-portion and a mouthpiece portion, sound absorbing material of non-fibrous nature within said transmitter portion and means for preventing back-pressure in said mufller during use, said back-pressure preventing means including a series of openings through the mufiler wall communicating the interior of the mufller with the outer atmosphere, certain of which openings being laterally located to improve tonal qualities, and a hollow exhaust box communicating with the muiller to introduce a tortuous path for the relief of air pressure without impairing the efflciency of the sound-retaining qualities.

6. In a voice muflier having a telephone transmitter engaging portion, which is of generally annular form and has a hollow upstanding inverted U-shaped part of crescent shape, and a mouthpiece portion readily attachable to and detachable from said transmitter-engaging portion; sound-absorbing material of non-fibrous nature within and completely filling said upstanding part and extending therebeyond into said mouthpiece portion, th mouthpiece portion having walls of non-uniform thickness, means for preventing back-pressure in said muiiler during use, said means including a series of openings through the thickened part of the walls of said mouthpiece portion forming narrow restricted passages communicating the interior or the muffler with the outer atmosphere, and being laterally located to improve tonal qualities, and a hollow exhaust box having openings communicating with the mouthpiece portion, and having other openings communicating the exhaust box with the outer atmosphere to introduce a tortuous path, all for relieving of air pressure without impairing the efiiciency of the sound-retaining qualities.

LOUIS S. SCHER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 730,101 Dunihue June 2, 1903 1,041,545 Williamson Oct. 15, 1912 1,419,606 Benedict June 13, 1922 1,425,958 Gelb Aug. 15, 1922 2,225,509 Schober Dec. 17, 1940 2,245,724 Scher June 17, 1941 FOREIGN PATENTS Number Country Date 26,315 Great Britain 1908 537,196 Germany Oct. 30, 1931

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