US3566310A - Waveguide for producing artificial reverberation - Google Patents

Waveguide for producing artificial reverberation Download PDF

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Publication number
US3566310A
US3566310A US741418A US3566310DA US3566310A US 3566310 A US3566310 A US 3566310A US 741418 A US741418 A US 741418A US 3566310D A US3566310D A US 3566310DA US 3566310 A US3566310 A US 3566310A
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US
United States
Prior art keywords
waveguide
irregularities
frequency range
reverberation
producing artificial
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US741418A
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English (en)
Inventor
Werner Fidi
Bernhard Weingartner
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AKG Acoustics GmbH
Original Assignee
AKG Akustische und Kino Geraete GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from AT409668A external-priority patent/AT279203B/de
Application filed by AKG Akustische und Kino Geraete GmbH filed Critical AKG Akustische und Kino Geraete GmbH
Application granted granted Critical
Publication of US3566310A publication Critical patent/US3566310A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K15/00—Acoustics not otherwise provided for
    • G10K15/08—Arrangements for producing a reverberation or echo sound
    • G10K15/10—Arrangements for producing a reverberation or echo sound using time-delay networks comprising electromechanical or electro-acoustic devices

Definitions

  • This invention relates to a oneor multi-dimensional mechanical waveguide, particularly a coil spring, for use in devices for producing artificial reverberation.
  • the audiofrequency signal is applied to the waveguide 4by an electromechanical transducer and is similarly picked up from the waveguide.
  • the coil springs are preferably excited to perform torsional vibration.
  • Any reverberator has a comb-like frequency response curve consisting of a succession of polar portions and zero portions, and these polar and zero portions must have a high density of distribution. This requires sufficiently long delay times. Periodicities in the time and frequency spectra must be avoided.
  • the signal which is applied should be subjected to a diffuse disintegration by a random dispersion. If the density of the distribution of the polar and zero portions of the frequency response curve is not sufiicient, any periodicity will result in a highly metallic, hollow and unnatural sound. With a higher density of distribution, such periodicity will result in -utter echoes or true echoes.
  • the use of one-dimensional homogenous delay lines results in strictly periodic frequency response curves.
  • the frequency response of the reverberation time is another significant factor and should drop toward the basses and toward the trebles.
  • the reverberation is produced as in the reverberatory chamber, in that the applied signal is delayed and is reflected many times.
  • the internal friction of the system will determine the reverberation time and the frequency response thereof.
  • measures are called for which ensure mainly the required dispersion as well as an adequate density of distribution of the frequency response curve. This is an object of the present invention.
  • the invention provides a waveguide. which is characterized in that it has a surface to which ⁇ an irregular shape has been imparted by a technological process so that the geometric dimensions of irregularities of said surface are smaller than the wavelength of the highest frequency to -be transmitted.
  • the propagation constant of waves travelling along the waveguide is so changed that a statistical variation is imparted to the propagation constant throughout the frequency range to be transmitted, and about a mean 'value which would be obtained in a waveguide which is free of such irregularities and other- Wise identical, so that the waveguide according to the invention results in a statistical dispersion of the sound transmitted by it and the final result is highly analogous to the reverberation conditions in the natural sound field.
  • etching processes may be used to produce the irregular surface according to the invention.
  • an irregularly distributed, acidresisting protecting layer eg. of a varnish, a grease, or another acid-resisting substance
  • the acid-resisting substance may be sprayed onto the surface to form small and very small, partly coherent droplets thereon.
  • the etchant will partly act under or through the protective layer after some time, so that a surface having any desired roughness or irregular texture can be obtained in dependence on the duration of the etching treatment.
  • defects on the surface of the waveguides may consist of minute cracks and scores which are produced when the wire is being drawn and is wound to form a coil spring. These defects result in an irregular attack by the etchant so that the desired irregular surface is produced.
  • the irregular surface may be produced by Sandblasting the waveguide.
  • the particle size and the nature of the treatment may be selected to produce a surface which embodies the inventive concept.
  • the required irregularities may be produced not only by a removal of material but also by changes effected in the structure of the material and preferably on the surface itself. Whereas such structural changes affect only the spring component, so that the result is less pronounced, it can well be utilized for the purposes of the invention.
  • a suitable material may be treated to have local zones differing in hardness and entirely irregularly distributed over the surface. These effects can be controlled by suitable tempering treatments.
  • FIG. l is a partial longitudinal sectional View of a portion of a waveguide, embodying the invention, and in the form of a coil spring;
  • FIG. 2 is a transverse sectional view of the coil spring.
  • the variations in wire diameter due t the irregularities amount to about -30%.
  • This variation has a particularly large effect on the mass components and spring components of a waveguide consisting of a coil spring, because the mass components are proportional to r3a2 and the spring components are proportional to r/4, where r represents the mean radius of the spring and a represents the Wire radius.
  • the waveguide according to the invention affords a close approach to the conditions which control the production of artificial reverberation.
  • a reverberation device provided with a waveguide according to the invention has a high fidelity.
  • said waveguide having a surface formed entirely with irregularities having geometric dimensions which are ⁇ smaller than the wavelength at the upper limit of said range, said irregularities being arranged to impart, to the propagation constant of waves traveling along said waveguide throughout said frequency range, a statistical variation about a mean value which would be obtained in an otherwise identical waveguide which is free of said irregularities.
  • said waveguide having a surface formed with irregularities having geometrical dimensions which are smaller than the wavelength at the upper limit of said range
  • said irregularities being arranged to impart, to the propagation constant of waves traveling along said waveguide throughout said frequency range, a statistical variation about a mean value which would be obtained in a waveguide which is free of said irregularities and otherwise identical,
  • said waveguide having a surface formed with irregularities having geometrical dimensions which are smaller than the wavelength at the upper limit of said range
  • said irregularities being arranged to impart, to the propagation constant of waves traveling along said waveguide throughout said frequency range, a statistical variation about a mean value which would be 0btained in a waveguide which is free of said irregularities and otherwise identical,
  • said process comprising Sandblasting a surface of a waveguide blank to produce said irregularities.
  • said waveguide having a surface formed with irregularities having geometrical dimensions which are smaller than the wavelength at the upper limit of said range
  • said irregularities being arranged to impart, to the propagation constant of waves traveling along said waveguide throughout said frequency range, a statistical variation about a mean value which could be obtained in a waveguide which is free of said irregularities and otherwise identical,
  • said waveguide having a surface formed with irregularities having geometrical dimensions which are smaller than the wavelength at the upper limit of said range, said irregularities being arranged to impart, to the propagation constant of waves traveling along said waveguide throughout said frequency range, a statistical variation about a mean value which would be obtained in a waveguide which is free of said irregularities and otherwise identical, said processing comprising:

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • ing And Chemical Polishing (AREA)
  • Springs (AREA)
  • Laminated Bodies (AREA)
US741418A 1967-07-05 1968-07-01 Waveguide for producing artificial reverberation Expired - Lifetime US3566310A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AT625467 1967-07-05
AT409668A AT279203B (de) 1968-04-26 1968-04-26 Ein- oder mehrdimensionaler Wellenleiter, insbesondere zu Torsionsschwingungen angeregte Schraubenfeder, für Geräte zur Erzeugung künstlichen Nachhalles

Publications (1)

Publication Number Publication Date
US3566310A true US3566310A (en) 1971-02-23

Family

ID=25600807

Family Applications (1)

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US741418A Expired - Lifetime US3566310A (en) 1967-07-05 1968-07-01 Waveguide for producing artificial reverberation

Country Status (7)

Country Link
US (1) US3566310A (pm)
BE (1) BE717613A (pm)
CH (1) CH477737A (pm)
DE (1) DE1762545B2 (pm)
FR (1) FR1572809A (pm)
GB (1) GB1206868A (pm)
NL (1) NL139403B (pm)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3723915A (en) * 1969-04-17 1973-03-27 Zenith Radio Corp Acoustic surface wave device

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3723915A (en) * 1969-04-17 1973-03-27 Zenith Radio Corp Acoustic surface wave device

Also Published As

Publication number Publication date
GB1206868A (en) 1970-09-30
BE717613A (pm) 1968-12-16
CH477737A (de) 1969-08-31
DE1762545A1 (de) 1970-07-02
DE1762545B2 (de) 1972-11-23
NL6809390A (pm) 1969-01-07
FR1572809A (pm) 1969-06-27
NL139403B (nl) 1973-07-16

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