US1996743A

US1996743A - Acoustic device

Info

Publication number: US1996743A
Application number: US722277A
Authority: US
Inventors: David G Blattner
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1934-04-25
Filing date: 1934-04-25
Publication date: 1935-04-09
Anticipated expiration: 1952-04-09

Description

April 1935- D. G. BLATTNER 1,996,743

CCCCCCCCCCCC CE Filed April 25, 1934 5 Sheets-Sheet l mm. mllllll j mmummllllllllllllu m mmnnllllmm ""lflllllllllm INVENTOR 'D G. BLA TTNER BY 0am 5. M

4 TTOR/VEV April 9, 1935. D. e. BLATTNER 1,996,743

ACOUSTIC DEVICE Filed April 25, 1934 3 Sheets-Sheet 2 FIG. 3

INVENTOR By 0.6.BLA TTNER mam a. M

A TTORNE V April 9, 1935.

D. G. BLATTNER ACOUSTIC DEVICE Filed April 25, 1934 3 Sheets-Sheet 3 lNVENTOR 0.6. BLA T7'NER Walla 6. M.

ATTORNEY I be understood more clearly and fully from the.

Patented Apr. 9, 1935 UNITED STATES PATENT OFFICE 1,996,143 ACOUSTIC DEVICE New York Application April 25, 1934, Serial No. 722,277

18 Claims.

This invention relates to acoustic devices and more particularly to horns suitable for use in conjunction with sound reproducing devices.

One object of this invention is to distribute a wide band of frequencies of importance in speech and music, uniformly and without perceptible distortion throughout a large sound field.

In one embodiment illustrative of this invention, a horn comprises a throat portion, a bend or intermediate portion coupled to one end of the throat portion, the bendportion changing the direction of sound waves approximately 90 degrees with respect to the longitudinal axis of the throat portion and distributing the sound waves uniformly through a large angular field, for example, 120 degrees, and a bell portion coupled to one end of the bend portion. The bell portion comprises four walls, two opposite walls being curved outwardly and symmetrically disposed with respect to a medial plane of the bell portion, passing through the outlet of the bend portion and disposed at substantially right angles to the longitudinal axis of the throat portion.

In accordance with a feature of this invention the bend and bell portions are provided with aligned, arcuate outlets of the same angle. Preferably the minimum dimension of the outlet or mouth of the bell portion is commensurate with times the wave-length of the lowest frequency to be transmitted by the horn so that the lower frequencies are. efliciently transmitted.

In accordance with another feature of this invention, the bend portion of the horn is so designed that the difference between the longest and shortest sound paths therethrough is less than one-half the wave-length of the highest frequency to be transmitted.

In accordance with still another feature of this invention, the bell portion is made of a length commensurate with one-quarter the wave-length of the lowest frequency to be transmitted whereby a substantially uniform and high radiation resistance is obtained throughout a large portion of the band of frequencies to be transmitted.

The invention and the features thereof will following detailed description with reference to the accompanying drawings in which:

Fig. 1 is a rear view of a loud-speaker including a horn constructed in accordance with this invention;

Figs. 2, 3 and 4 are front, side and top views respectively of the loud-speaker shown in Fig. 1;

Fig. 5 is a diagrammatic view showing the contour of the inner surfaces of the throat portion of the horn, in a plurality of planes along the length of the sound passageway in the throat portion;

Fig. 6 is an enlarged front view of the bend portion of the horn;

Fig. 7 is a side view of the bend portion in cross-section along line 1-1 of Fig. 6; and

Fig. 8 is a diagrammatic view showing the contour of the inner surfaces of the walls of the bend portion of the horn in a plurality of angularly displaced planes along the sound passageway in the bend portion.

Referring now to the drawings, the horn illustrative of this invention comprises, in general, a throat portion In, a bend portion II, and a bell portion I2, all of which may be cast of a metal such as aluminum, or fabricated in other ways of suitable materials. A sound translating device l3, for example, an electrodynamic receiver of the type disclosed in Patent 1,707,545 granted April 2, 1929 to Edward C. Wente, is acoustically coupled to the inlet end of the throat portion 10.

The throat portion In has'a linear sound passageway which, as indicated in Fig. 5, varies in cross-section from a circle in a sectional plane M at its lower or inlet end to substantially a sector in a sectional plane F at its upper or outlet end. In Fig. 5, the several outline figures, F to M inclusive, indicate the configuration of the inner surfaces of the throat portion bounding the sound passageway therethrough, in equally spaced planes along the length of the sound passageway, the planes being indicated by the corresponding letters F to M in Fig. 3. The throat portion I0 is provided at its upper or outlet end with a flange H, which may be cast integrally with the throat portion. ribs I5 being provided to reinforce the throat portion adjacent the flange.

The bend portion H, shown clearly in Figs. 6, 7 and 8, is provided at its inlet end with an integral flange l6 which is seated upon and is secured to the flange I4 by bolts H, the walls of the bend portion adjacent the flange l6 being reinforced by ribs I8. As is apparent, particularly from Fig. 7, the bend portion includes a sound passageway l9 which directs the sound waves through 90 degrees with respect to the longitudinal axis of the sound passageway in the throat portion to and terminates in an arcuate recbounded by two arcuate top and bottom walls ,2I and 22, respectively, provided with reinforcing ribs 23, and angularly disposed side walls 24, the disposition of which is clearly shown in Fig. 4. The sound pasageway I 9 is of the same form and area at its inlet end, as indicated by the outlined figure F in Fig. 8, as the outlet end of the throat passageway, and varies in contour along its length as indicated in Fig. 8. In this figure, the outlined figures A to F show the contour of the sound passageway in angularly spaced planes correspondingly indicated by the characters A to F in Fig. '7. The bend portion is provided at its outlet end with an integral rim or flange 25 to which the bell portion of the horn may be secured.

The bell portion of the horn comprises similar top and bottom sections provided with side flanges 26 which are secured together by a plurality of bolts 21. The top and

bottom walls

28 and 29, respectively, are each provided with radial reinforcing ribs 30 and with arcuate reinforcing ribs 3 I. The side walls 32 of the bell portion are straight and angularly displaced and, as shown in Fig. 4, are coplanar with the corresponding side walls 24 of thebend portion II. The bell portion is provided at its inlet end with an arcuate flange 33 which is suitably secured, as by bolts 34, to the flange or rim 25' on the bend portion I I. The inlet end of the bell portion is provided with an arcuate rectangular inlet of the same area as the outlet 20 of the bend portion. The mouth 35 of the horn is also of arcuate rectangular form. As clearly shown in Fig. 3 the top and

bottom walls

28 and 29 are curved away from and symmetrically disposed with respect to the medial plane, indicated by the line X, passing through the outlet 20 of the bend section I I and at right angles to the longitudinal axis of the sound passageway in the throat portion.

It will be apparent that the area of the sound passageway in the horn increases smoothly between the inlet end of the throat portion II) and the mouth 35 of the horn. Preferably the several portions of the horn are so designed that this area increases exponentially with length between the inlet of the throat portion I and the mouth 35.

It has been found that the configuration above described of the sound pasageway in the bend portion is particularly desirable and advantageous inasmuch as it prevents material suppression of high frequencies and hence results in a uniform distribution of all frequencies of importance in the band to be transmitted, and particularly the higher frequencies from the throat portion into the-bell portion of the horn.

Inasmuch as the

openings

20 and 35 are of the same form and angle and also are in alignment, sound waves issuing from the bend portion will be distributed uniformly through the angle demately 120 degrees.

termined by the disposition of the walls, each consisting of one wall 24 of the bend portion and one wall 26 of the bell portion, with respect to each other. In the specific embodiment of the invention shown, the angle of distribution is approxi- It will be understood, of course, that a greater or smaller angle may be used if desired.

In order to'insure efiicient and adequate radiation of the lower frequencies, the length of the bell portion preferably is made approximately one-quarter the wave-length corresponding to the lowest frequency it is desired to transmit.

This proportioning insures a substantially unitangular outlet 20. The soundpassageway I9 isform and high radiation resistance throughout a large portion of the band of frequencies to be transmitted. To further insure eificient transmission of' the lower frequencies, the minimum dimension of the mouth of the bell portion of the horn preferably is made times the wave=length corresponding to the lowest frequency to be transmitted.

Furthermore, in order to insure a uniform distribution of all and particularly the high frequencies throughout the entire sound field of the horn, it has been found desirable to so proportion the bend portion of the horn that the difference between the longest and shortest sound paths therethrough; is not greater than one-half the wave-length of the highest frequency it is desired to transmit.

Although a specific embodiment of the invention has been shown and described, it is to be understood, of course, that many modifications may be made therein without departing from the scope and spirit of this invention as defined in the appended claims.

What is claimed is:

l. A horn comprising a throat portion, a bend portion coupled to said throat portion and having an arcuate outlet, and a bell portion coupled to said bend portion and having an arcuate mouth, the center of said mouth being in alignment with the center of said outlet.

2. A horn comprising a throat portion, a 90 degree bend portion coupled to said throat portion and having an arcuate rectangular outlet, and a bell portion coupled to said bend portion and disposed with its longitudinal axis at substantially right angles to said throat portion, said bell portion having an arcuate rectangular mouth coaxial with said outlet, the arc of said outlet being of the same angle as the arc of said mouth.

3. A horn comprising a throat portion, a bell portion at an angle to said throat portion and having an arcuate mouth, and an intermediate portion coupling said throat and bell portions, corresponding, side walls of said bell and intermediate portions lying in the same plane;

4. A horn comprising a throat portion, a bell portion having ari arcuate rectangular mouth at substantially right angles to said throat portion, and a 90 degree bend portion coupling said throat and bell portions, corresponding side walls of said bell and bend portions lying in the same plane, and the top and bottom walls of said bell portion flaring symmetrically with respect to a medial plane of said bell portion at substantially right angles to said throat portion.

5. A horn'comprising a throat portion, abell portion at an angle to said throat portion, and a bend portion coupling said throat and bell portions, the inner walls of said bend portion forming a passageway of substantially sectoral crossse'ction at the end coupled to said throat portion and increasing smoothly to an arcuate section at the end coupled to said bell portion.

6. A horn comprising a throat portion, a bell portion, and a bend portion coupling said throat and bell portions, said bend portion having a sound passageway which is substantially sectoral in cross-section at the end coupled to said throat portion and which increases smoothly to an arcuate rectangular outlet at the end coupled to saidbell portion, said bell portion having an arcuate rectangular mouth in axial alignment with said outlet, the arcs of said outlet and of said mouth being of the same angle.

7. A horn comprising a throat portion having an outlet substantially sectoral in cross-section, a bend portion having an inlet of the same form as and communicating with said outlet, the passage in said bend portion curving through 90 degrees and terminating in an arcuate rectangular outlet, and a bell portion having an arcuate inlet communicating with said arcuate outlet, and having an arcuate mouth of the same angle as said arcuate outlet.

8. A horn comprising a throat portion having a circular inlet and a substantially sectoral outlet, a bend portion having a sectoral inlet coupled to said outlet and having an arcuate outlet, and a bell portion having an arcuate inlet coupled to said second outlet.

9. A horn comprising a linear throat portion having a circular inlet and a sectoral outlet, a 90 degree bend portion having a sectoral inlet coupled to said outlet and having an arcuate rectangular outlet, and a bell portion having an arcuate rectangular inlet coupled to said second outlet and having an arcuate rectangular mouth in alignment with said second outlet.

10'. A horn in accordance with claim 9 in which the arcuate rectangular outlet and the arcuate rectangular mouth are of the same angle.

11. A horn comprising a throat portion, a bell portion at an angle to said throat portion, and a bend portion connecting said throat and bell portions, the difference between the longest and shortest sound paths through said bend portion being not greater than one-half the wave-length of the highest frequency to be transmitted.

1.2. A horn comprising a linear throat portion, a bell portion at substantially right angles to said throat portion, and a 90 degree bend portion coupling said throat and bell portions, the difference between the longest and shortest sound paths through said bend portion being not greater than one-half the wave-length of the highest frequency to be transmitted.

13. A horn comprising a throat portion and a bell portion disposed at an angle to said throat portion, said-bell portion hav a length of substantially one-quarter the wave-length of the lowest frequency to be transmitted.

14. A horn comprising a throat portion and a. bell portion disposed at substantially right angles to said throat portion, said bell portion having a length of substantially one-quarter the wavelength of the lowest frequency to be transmitted, and having a rectangular arcuate mouth.

15. A horn comprising a throat portion having an outlet sectoral in cross-section, an intermediate portion having an inlet sectoral in cross-section communicating with the outlet of said throat portion, the passage in said intermediate portion curving through 90 degrees and terminating in a 120 degree arcuate outlet, and a bell portion having a 120 degree inlet communicating with the outlet of said intermediate portion, said bell portion having also a 120 degree outlet.

16. A horn comprising a throat portion, a bell portion having a 120 degree arcuate outlet, a horizontal medial plane of said bell section being substantially perpendicular to a plane through the axis of said throat portion, the sound passage area in each section increasing progressively in accordance with the exponential law.

17. A horn comprising a throat portion and a bell portion, at an angle to said throat portion, said bell'portion terminating in a mouth, the smallest dimension of which is substantially times the wave-length of the lowest frequency times the wave-length of the lowest frequency to be transmitted.

DAVID G. BLA'ITNER.