US1760252A - Multiple resonant acoustic device - Google Patents

Description

May 27, 1930. A. M L. NICOLSON MULTIPLE RESONANT ACOUSTIC DEVICE Filed Sept. 17, 1927 INVENTOR ALEXANDER McLEAN NICOLSUN 2 M W ATTORNEY Patented May 27, 1930 UNIT-ED sra rrz's' PATENT OFFICE ALEXANDER IOLEAN 'NICOLSON, OFQIEW N. 11,-M61103, BY KESNE ASSIGN- KIEDT'JJS, TO mm TELEGRAPH COMPANY, A'COBPORATION' OF CALIFORNIA.

mmm ansoztmr acou's'rrc mavrcn Application m member-17,1327. Serial ll'o. $0,072. I

a device of the class described, which shall reproduce the sound desired with a high degree of fidelity and with minimum distortion.

' It is a further object of this invention to w provide such'a device which will not-require the use of excessive power for high quality reproduction as is the case in most systems at present in use. I v

It is a. further object of this invention to providea device of the class described, which 2 may be constructed and operated at-minimum cost.

' Still further objects and advantages of my invention will, be apparent from the specification.

The features be. characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its fundamental principles and as to its particular embodiments will best be understood byreference to'the specificationand accompanyin the form of horns, cones, discs, or the like.

The various sound generating elements are arranged to have difierent natural frequencies disposed over the range desired to be reproduced, and preferably a suflicient number .of such devices will be provided so that for any sound frequency which it is desired to reproduce, at least one ofsaid elements responds at a frequency in the neighborhood of its natconsiderable amplification of sound is obconversely, permitting the usual volume of sound with a considerably less power input,

of novelty which I believe to.

ural frequency. As a result, it will be understood that the resonance of each element comesinto action in'such manner that no matter which frequency is being reproduced, a

tained through the natural resonance of some one or more of the sound reproducing ele-' ments, 1 thereby producing the maximum sound response for minimum power input, or

thereby permittingthe substitution of conventional amplifying tubes for so-called power'tubes in audio frequency amplifiers withouta substantial decrease in the volume or quality of sound output. I v f Preferably, a single means is utilized for energizing all of the sound generating. elements, which means may take the form of the usual electromagnetic driver, or-an electrostatic driver however, for certain pur poses, I prefer touse a piezo-electric crystal device of anysuitable type well known in the art, such for example, as a crystal of Rochelle salt exhibiting the well known hour glass cons figuration, or, various improved forms thereof, such as described and claimed in my copending applications, entitled Cast piezoelectric device, Serial Number 155,897,fi1 ed December 20, 1926: Composite piezo-electriccrystal device;Serial' Number 155,898, filed December 20, 1926: Composite piezo-electric torsion device, Serial Number 155,899, filed March 11, 1927 Internally clamped composv ite piezoelectric torsion device, Serial Numher 155,900, filed Dec.,20, 1926; Method and apparatus for producing electric oscilla-- tions, Serial Number 155,901,1iled Dec. 20, 1926:- and, Mechanical coupling for piezoelectric crystal device, Serial Number 160,-

360, filed Jan. 11, 1927.

- In the preferred form of my invention, a a single piezo-electric crystal device is utilized having a stress plate rigidly connected thereto and adapted to be vibrated by the crystal device when electrical oscillations are 1 impressed thereon. The said stress plate is provided with mechanical terminals, each adapted to energize one of the sound generating elements. The sound generating elements,

I themselves, may, for example, be in the form y and 2, 1 designates a piezoelectric crystal device such as a crystal of Rochelle salt exhibiting the well known hour glass configuration and having an exterior belt electrode 2, of conducting material, such as a layer of metal foil or the like,.and an internal electrode 3- passing through an opening formed within the crystal normal to the plane of the base thereof. ,The crystal 1 may be mounted upon a suitable base plate 4 and a suitable stress plate 7 of elastic material such as steel, is rigidly secured to the top face thereof. The crystal 1, the base plate 4, and the stress plate 7 may be secured in any desired relation and a compressive bias exerted upon the crystal by providing the electrode 3 in the form of a bolt having a head 5 engaging the base plate and provided with a suitable nut 6 at its 0pposite end, by means of which the desired compression may be exerted upon the crystal.

If now, a difference of potential be impressed'between the electrodes 2 and 3, the crystal itself will tend to deform in a manner such that the stress plate 7 will rotate slightly with respect to the base plate 4, as is Well known: and, if an alternating electromotive force be impressed, the deformation will be proportional in amplitude and frequency to the impressed electromotive force.

Connected to the stress plate 7, I provide a plurality of sound reproducing elements, such for example as cones 10, 11, 12, 13, 14, 15, 16 and 17 it being understood that the size, shape and material of the sound generating elements are so chosen that each of these elements has a natural resonant frequency of response different from that of the other elements, and distributed over the range of frequencies which it is desired to I apexes to the stress plate 7 by means of suitable bolts 18 engaging tapped holes in the stress plate 7. Suitable filling blocks 19 may be utilized to reinforce the apexes of the various cones and serve to hold the bolt heads. Suitable extensions 20, 24, 25, 26, 27, 28 and 29 may be provided on the stress plate 7, if

desired, to which the soundgenerating ele' ments may be directly attached, but-these may be omitted under certain conditions. It will be understood that by the proper proportionjug and shape of said extensions, the resonant frequency of the corresponding sound generating elements may be modified or otherwise influenced. In addition, parts of the stress plate 7 may be cut away or otherwise removed, to form as many openings such as 21 .as may be desired, or external sections may he removed as at 22 and 23 to form neck por' tions: also, the extensions may be given any suitable shape as 20, 28 and 29, all of the said modifications of the form of stress plate 7 serving to alter the natural frequency of response of the sound generating elements by alteration of the mass and elasticity of each individual'sound generatingelement.

lVhile I have shown cones 10, 11, 12, 13,

15 and 17 as straight side cones, and cones edge at the throat of the horn, preferably in the form of a relatively smallcone having its apex pointing toward the bell of the horn. In the arrangement shown, the .horns are preferably made of suitable light material such as paper or the like, so as to be entirely supported and carried on the diaphragms 33, 34 and 35, whereby the horn'itself as well as the air enclosedthereby, is subject to vibration.

As an alternative,a single dia hragm may be utilized feeding all of the orns which' may all be connected to the sound box in which the diaphragm operates in such an arrangement, it will usually be preferable to construct the horns of heavier material and to make use only of the vibration of the air enclosed in the horns, the horns, themselves, not being directly vibrated except through the vibration of the air contained therein.

\Vhile I have shown and described my invention as a sound reproducer, it should be understood that it may be utilized also as a microphone; that is to say, when sound waves are-permitted to fall upon it, it will deliver an electromotive force proportional in frequency and amplitude to such sound waves.

"While I have'shown and described certain preferred embodiments of my invention, it will be understood that modifications and changes may be made without departing. from the spirit and scope of my invention, as will be understood by those skilled in the art.

claim 1,. A sound reproducing device comprising a multiplicity of sound generating elements, each of said sound generating elements having a di lferent natural frequency of response said elements being so arranged that the response frequencies are distributed over the range of frequencies to reproduced, a resilient plateadapted to be shaped to predetcrmine its acoustic characteristics, and a single means connected to said resilient plate for energizing all of said sound reproducing elements.

2. A sound reproducing device comprising; a multiplicity of acoustic amplifying, elements having different natural frequencies, said elements being so constructed that the natural frequencies of response are distributed over the band of frequencies desired to be reproduced by said device, a metallic plate. means for securing said elements to said plate, and a single means secured to said plate for energizing all of said amplifying elements.

3. A sound reproducingdevice comprising a multiplicity of acoustic amplifying elements having different natural frequencies, said elements being so constructed that the natural frequencies of response are distributed over the band of frequencies desired to be reproduced by said device, and a single means attached to said amplifying elements for energizing all of said amplifying elements, said means comprising a piezoelectriccrystal.

Signed at New York city, in the county of New York and State of New York this 16th day of September, A. D. 1927.

ALEXANDER McLEAN NKCQLSON.

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