WO1996011558A1 - Omnidirectional sound source - Google Patents

Omnidirectional sound source Download PDF

Info

Publication number
WO1996011558A1
WO1996011558A1 PCT/DK1995/000399 DK9500399W WO9611558A1 WO 1996011558 A1 WO1996011558 A1 WO 1996011558A1 DK 9500399 W DK9500399 W DK 9500399W WO 9611558 A1 WO9611558 A1 WO 9611558A1
Authority
WO
WIPO (PCT)
Prior art keywords
loudspeaker
sound source
cabinet
sound
coupler
Prior art date
Application number
PCT/DK1995/000399
Other languages
French (fr)
Inventor
Jean-Dominique Polack
Original Assignee
A/S Brüel & Kjær
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
Application filed by A/S Brüel & Kjær filed Critical A/S Brüel & Kjær
Priority to AU36044/95A priority Critical patent/AU3604495A/en
Publication of WO1996011558A1 publication Critical patent/WO1996011558A1/en

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
    • H04R1/32—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only
    • H04R1/34—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only by using a single transducer with sound reflecting, diffracting, directing or guiding means

Definitions

  • the invention relates to a sound source comprising a loudspeaker which in one direction radiates into a hollow coupler with an open inlet communi- eating with and being closed by said loudspeaker as well as with an open outlet, said coupler comprising rigid walls which cannot respond to the sound pressures produced by the loudspeaker and which are of a sectional area decreasing in a direction away from the loudspeaker, whereby the loudspeaker radiates into a cabinet in the opposite direction.
  • US-PS No. 4,206,831 discloses a loudspeaker provided with a coupler and a cabinet.
  • the object of the invention is to provide an omnidirectional sound source.
  • a sound source of the above type is according to the invention character ⁇ ised in that the sectional area of the cabinet decreases in a direction away from the loudspeaker. Tests have shown that in this manner it is avoided that the cabinet gives shade from radiation in the rearward direction with the result that a substantially ball-shaped radiation characteristics is obtained inside a relatively large frequency range.
  • the cabinet may be cone-shaped, optionally frustoconical.
  • the cone-shaped cabinet may according to the invention have a cone angle of maximum 1 5°. In this manner the shade area is further reduced.
  • the coupler may be cone-shaped and have a cone angle which is smaller than the cone angle of the cabinet.
  • the cone-shaped coupler has a cone angle of approximately 8°.
  • Fig. 1 illustrates an omnidirectional sound source according to the inven- tion
  • Fig. 2 illustrates extreme deviations from omnidirectional radiation as func ⁇ tion of the frequency, the international standards being marked, and
  • Fig. 3 illustrates the radiation characteristics as function of the angle.
  • a high number of loudspeakers are arranged on a ball surface.
  • the ball is approxi- mated by a regular polyhedron.
  • Sound sources are known which are prod ⁇ ucts based on tetrahedron, cubes (hexahedron), octahedron, and icosa- hedron.
  • a loudspeaker is mounted on each surface of the polyhedron, an all the loudspeakers are phase-fed.
  • the spreading in loudspeaker char- acteristics and the phase-variation, especially in the frequency range ex ⁇ ceeding 1 kHz cause interference patterns influencing the directional char ⁇ acteristics.
  • an omnidirectional sound source is provided of a characteristics comparable with the characteristics of the known polyhedron sources.
  • the perfect omnidirectional source is a concentrated source. The diameter of the sound-radiating opening of the source has therefore been reduced until the deviations from the omnidirectional radia ⁇ tion are within the tolerances.
  • the sound source comprises 4 elements, viz.
  • the omnidirectional sound source must, however, be carefully dimen ⁇ sioned. Not only the size of the cabinet 8 is important for the coverage of the desired frequency area. Also the outer shape is of importance for providing the directional characteristics according to the international standards.
  • Fig. 2 illustrates the results of the final embodiment of the sound source, where the cabinet 8 is encased in a conical or frustoconical housing corre ⁇ sponding to a horn with a connecting cylinder between the two cones reduced to 10 mm.
  • the results are within the tolerances of the interna ⁇ tional standards whereby it is assumed that the central frequency of each band reflects the behaviour of the entire band.
  • the sound source is shaped in the following manner:
  • First the diameter of the aperture is chosen: For a predetermined set of directional tolerances either for octave or third octave bands the optimum radius of the aperture and the maximum deviation must be determined for each band.
  • the loudspeaker 6 is chosen. As only a few percentages of the sound effect is radiated, the chosen loudspeaker must be as sensitive and as powerful as possible within the band being of interest. The latter requires, however, a heavy sound source of a large diameter, which means increased difficulties in satisfying the directional requirements in the shade area behind the cabinet 8. The choice of loudspeaker 6 is therefore a compromise between sensitivity, power, and size.
  • the dimensions of the conical horn 4 are determined. Two dimen ⁇ sions of the cone have already been determined during the previous steps, viz. the diameter of the aperture 2 and the total diameter of the loud ⁇ speaker 6. The last dimension is the length of the horn 4, which must meet two requirements, viz. that half the aperture angle at the point of the cone must be less than 1 5° because the shade area should be minimized, and that the Helmholtz resonance of the source must be adapted to the lowest frequency of interest.
  • the shape is evaluated.
  • the evaluation is performed by ways of simulations rendering it possible to calculate the electric impedance and to control the resonance of the cabinet 8 and the entire frequency reproduc ⁇ tion in order to control the low frequency cut-off, the total sound level, and the horn resonances.
  • the Thiele-Small parame ⁇ ters describe nothing but the low frequency reproduction of a loudspeaker.
  • the high frequency area of the sound source, where the horn 4 is of vital importance, cannot therefore be accurately simulated.
  • the diameter of the loudspeaker 6 must be as small as possible, and the cabinet 8 must be shaped with a gradually decreasing cross section in the rearward direction.
  • the cabinet 8 is prefer ⁇ ably conical, optionally frustoconical with a cone angle exceeding the cone angle of the horn 4, the latter cone angle preferably being approximately 8°.
  • the sound source according to the invention is manufactured in the fol ⁇ lowing manner:
  • a loudspeaker is provided and the Thiele-Small parameters are measured.
  • the Thiele-Small parameters indicated by the producers are often too high.
  • a simulation is performed with topical data in order to obtain an evaluation of the power level of the source.
  • a prototype is designed of the sound source and it is manufactured.
  • the impedance curve is measured in order to determine the Helmholtz and the cabinet resonances.
  • Deviations from omnidirectional radiation are measured in a sound-dead room. The best results are obtained at large distances from the source. According to the standards, the distance must, however be 1 .5 m.
  • the power level is measured in a reverberation chamber.
  • the sound source is of a total length of 353 mm, the cabinet being of a length of 23 mm and the horn being of a length of 330 mm.
  • the diameter of the aperture is typically 38 mm.
  • Both the horn and the cabinet may optionally contain sound-absorbing material.
  • Fig. 3 illustrates the radiation characteristics at 500 Hz as function of the angle ⁇ relative to the longitudinal axis which means that the sound source is facing upwards as shown in Fig. 1 . It appears that the radiation charac ⁇ teristics is substantially circular.

Abstract

A sound source comprising a loudspeaker (6) and a hollow coupler (4) with an open inlet which communicates with and is closed by the loudspeaker (6) and an open outlet, said coupler (4) comprising rigid walls which cannot respond to the sound pressures produced by the loudspeaker (6). According to the invention the loudspeaker (6) comprises a cabinet (8) being narrowed down in the rearward direction. In this manner it is avoided that the cabinet (8) gives a shade from the radiation in the rearward direction, whereby a substantially omnidirectional characteristics is obtained within a relatively large frequency range.

Description

Title: Omnidirectional sound source.
Technical Field
The invention relates to a sound source comprising a loudspeaker which in one direction radiates into a hollow coupler with an open inlet communi- eating with and being closed by said loudspeaker as well as with an open outlet, said coupler comprising rigid walls which cannot respond to the sound pressures produced by the loudspeaker and which are of a sectional area decreasing in a direction away from the loudspeaker, whereby the loudspeaker radiates into a cabinet in the opposite direction.
Background Art
US-PS No. 4,206,831 discloses a loudspeaker provided with a coupler and a cabinet.
Description of the Invention
The object of the invention is to provide an omnidirectional sound source.
A sound source of the above type is according to the invention character¬ ised in that the sectional area of the cabinet decreases in a direction away from the loudspeaker. Tests have shown that in this manner it is avoided that the cabinet gives shade from radiation in the rearward direction with the result that a substantially ball-shaped radiation characteristics is obtained inside a relatively large frequency range.
According to a particularly advantageous embodiment of the invention, the cabinet may be cone-shaped, optionally frustoconical.
The cone-shaped cabinet may according to the invention have a cone angle of maximum 1 5°. In this manner the shade area is further reduced.
Furthermore according to the invention the coupler may be cone-shaped and have a cone angle which is smaller than the cone angle of the cabinet.
According to a particularly advantageous embodiment, the cone-shaped coupler has a cone angle of approximately 8°.
Brief Description of the Drawing
The invention is explained in greater detail below with reference to the accompanying drawings, in which
Fig. 1 illustrates an omnidirectional sound source according to the inven- tion,
Fig. 2 illustrates extreme deviations from omnidirectional radiation as func¬ tion of the frequency, the international standards being marked, and
Fig. 3 illustrates the radiation characteristics as function of the angle.
Description of the Preferred Embodiments of the Invention
A demand exists for omnidirectional sound sources to be used by the control of building acoustics. First, new guidelines for measuring sound isolation indicate that an omnidirectional sound source must be used. Sec¬ ondly, advanced architectural-acoustic indications depend highly on the specific direction of the sound source, which has resulted in recommenda- tions with respect to the radiation characteristics.
By the known approximations for omnidirectional sound sources, a high number of loudspeakers are arranged on a ball surface. The ball is approxi- mated by a regular polyhedron. Sound sources are known which are prod¬ ucts based on tetrahedron, cubes (hexahedron), octahedron, and icosa- hedron. Then a loudspeaker is mounted on each surface of the polyhedron, an all the loudspeakers are phase-fed. The spreading in loudspeaker char- acteristics and the phase-variation, especially in the frequency range ex¬ ceeding 1 kHz cause interference patterns influencing the directional char¬ acteristics. The various standards require, however, only guideline measur- ings in wide bands (1 /3 octave or one octave) for providing a 30° sliding average.1 2 or 20 loudspeakers take up relatively much room which results in heavy voluminous sources typically weighing more than 1 2 kg and being of a diameter of approximately 50 cm.
According to the invention, an omnidirectional sound source is provided of a characteristics comparable with the characteristics of the known polyhedron sources. The perfect omnidirectional source is a concentrated source. The diameter of the sound-radiating opening of the source has therefore been reduced until the deviations from the omnidirectional radia¬ tion are within the tolerances.
A sound source structured according to this principle is shown in Fig. 1 . The sound source comprises 4 elements, viz.
a) a powerful loudspeaker 6
b) a hollow coupler with rigid walls in form of a horn 4 communicating with and being closed by the loudspeaker and concentrating the sound and transmitting said sound to an aperture 2,
c) an aperture 2 diffracting sound in ail directions,
d) a cabinet 8 being narrowed down in the rearward direction and re¬ ducing the diffraction. These elements are tested separately, and it turned out that it is possible to provide an omnidirectional sound source operating substantially as a concentrated source. A powerful loudspeaker 6 is, however, relatively expensive, but compared to the 12 loudspeakers necessary previously it does not present an increase in cost. In addition, the use of only one loudspeaker 6 increases the reliability.
The omnidirectional sound source must, however, be carefully dimen¬ sioned. Not only the size of the cabinet 8 is important for the coverage of the desired frequency area. Also the outer shape is of importance for providing the directional characteristics according to the international standards.
Fig. 2 illustrates the results of the final embodiment of the sound source, where the cabinet 8 is encased in a conical or frustoconical housing corre¬ sponding to a horn with a connecting cylinder between the two cones reduced to 10 mm. The results are within the tolerances of the interna¬ tional standards whereby it is assumed that the central frequency of each band reflects the behaviour of the entire band.
The sound source is shaped in the following manner:
i) First the diameter of the aperture is chosen: For a predetermined set of directional tolerances either for octave or third octave bands the optimum radius of the aperture and the maximum deviation must be determined for each band.
ii) Then the loudspeaker 6 is chosen. As only a few percentages of the sound effect is radiated, the chosen loudspeaker must be as sensitive and as powerful as possible within the band being of interest. The latter requires, however, a heavy sound source of a large diameter, which means increased difficulties in satisfying the directional requirements in the shade area behind the cabinet 8. The choice of loudspeaker 6 is therefore a compromise between sensitivity, power, and size.
iii) Then the dimensions of the conical horn 4 are determined. Two dimen¬ sions of the cone have already been determined during the previous steps, viz. the diameter of the aperture 2 and the total diameter of the loud¬ speaker 6. The last dimension is the length of the horn 4, which must meet two requirements, viz. that half the aperture angle at the point of the cone must be less than 1 5° because the shade area should be minimized, and that the Helmholtz resonance of the source must be adapted to the lowest frequency of interest. As the securing of the loudspeaker 6 at the bottom of the horn 4 results in an increase of the apparent length of the horn 4, the last requirement necessitates calculations of the length of the horn 4 optionally by way of successive approximations until the Helmholtz resonance is correct. The latter is performed by means of the following step iv.
iv) Then the shape is evaluated. The evaluation is performed by ways of simulations rendering it possible to calculate the electric impedance and to control the resonance of the cabinet 8 and the entire frequency reproduc¬ tion in order to control the low frequency cut-off, the total sound level, and the horn resonances. It should be noted that the Thiele-Small parame¬ ters describe nothing but the low frequency reproduction of a loudspeaker. The high frequency area of the sound source, where the horn 4 is of vital importance, cannot therefore be accurately simulated.
v) Then the directive and the cabinet design is evaluated. A few principles in the design must be observed. The diameter of the loudspeaker 6 must be as small as possible, and the cabinet 8 must be shaped with a gradually decreasing cross section in the rearward direction. The cabinet 8 is prefer¬ ably conical, optionally frustoconical with a cone angle exceeding the cone angle of the horn 4, the latter cone angle preferably being approximately 8°.
The sound source according to the invention is manufactured in the fol¬ lowing manner:
A loudspeaker is provided and the Thiele-Small parameters are measured. The Thiele-Small parameters indicated by the producers are often too high. Then a simulation is performed with topical data in order to obtain an evaluation of the power level of the source. A prototype is designed of the sound source and it is manufactured.
In order to control whether the sound source meets the requirements, the following measurements must be carried out.
i) The source is weighed.
ii)The impedance curve is measured in order to determine the Helmholtz and the cabinet resonances.
iii) The frequency reproduction is measured, whereby it is possible to determine the horn resonances.
iv) Deviations from omnidirectional radiation are measured in a sound-dead room. The best results are obtained at large distances from the source. According to the standards, the distance must, however be 1 .5 m.
v) The power level is measured in a reverberation chamber.
In a specific embodiment, the sound source is of a total length of 353 mm, the cabinet being of a length of 23 mm and the horn being of a length of 330 mm. The diameter of the aperture is typically 38 mm. Both the horn and the cabinet may optionally contain sound-absorbing material. Fig. 3 illustrates the radiation characteristics at 500 Hz as function of the angle θ relative to the longitudinal axis which means that the sound source is facing upwards as shown in Fig. 1 . It appears that the radiation charac¬ teristics is substantially circular.

Claims

Claims
1. A sound source comprising a loudspeaker (6) which in one direction radiates into a hollow coupler (4) with an open inlet communicating with and being closed by said loudspeaker (6) as well as with an open outlet, said coupler (4) comprising rigid walls which cannot respond to the sound pressures produced by the loudspeaker (6) and which are of a sectional area decreasing in a direction away from the loudspeaker (6), whereby the loudspeaker (6) radiates into a cabinet (8) in the opposite direction, c h a r a c t e r i s e d in that the sectional area of the cabinet (8) decreases in a direction away from the loudspeaker (6).
2. A sound source as claimed in claim 1, c h a r a ct e r i s ed in that the cabinet (8) is cone-shaped, optionally frustoconical.
3. A sound source as claimed in claim 2, c h a r a c t e ri s e d in that the cone-shaped cabinet (8) has a cone angle of maximum 15°.
4. A sound source as claimed in any of the preceding claims, c h a rac¬ t e r i s e d in that the coupler (4) is cone-shaped and has a cone angle which is smaller than the cone angle of the cabinet (8).
5. A sound source as claimed in claim 4, c h a r ac t e r i se d in that the cone-shaped coupler (4) has a cone angle of approximately 8°.
6. A sound source as claimed in one or more of the preceding claims, ch aracterised in that the coupler (4) comprises a sound-absorbing material.
7. A sound source as claimed in one or more of the preceding claims, characterised in that the cabinet (8) comprises a sound-absorbing material.
PCT/DK1995/000399 1994-10-10 1995-10-06 Omnidirectional sound source WO1996011558A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU36044/95A AU3604495A (en) 1994-10-10 1995-10-06 Omnidirectional sound source

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DK117494A DK171338B1 (en) 1994-10-10 1994-10-10 Circular sound source
DK1174/94 1994-10-10

Publications (1)

Publication Number Publication Date
WO1996011558A1 true WO1996011558A1 (en) 1996-04-18

Family

ID=8101829

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/DK1995/000399 WO1996011558A1 (en) 1994-10-10 1995-10-06 Omnidirectional sound source

Country Status (3)

Country Link
AU (1) AU3604495A (en)
DK (1) DK171338B1 (en)
WO (1) WO1996011558A1 (en)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0984662A2 (en) * 1998-09-03 2000-03-08 Bose Corporation Waveguide electroacoustical transducing
FR2828784A1 (en) * 2001-08-17 2003-02-21 Etienne Bardier Loudspeaker homogeneous bass sound transmission having guide tube axially placed loudspeaker membrane with surface around tube with structure enclosure held.
EP2218266A1 (en) * 2007-11-09 2010-08-18 Koninklijke Philips Electronics N.V. Alert device and method
US8265310B2 (en) 2010-03-03 2012-09-11 Bose Corporation Multi-element directional acoustic arrays
US8295526B2 (en) 2008-02-21 2012-10-23 Bose Corporation Low frequency enclosure for video display devices
US8351630B2 (en) 2008-05-02 2013-01-08 Bose Corporation Passive directional acoustical radiating
US8351629B2 (en) 2008-02-21 2013-01-08 Robert Preston Parker Waveguide electroacoustical transducing
CN102883252A (en) * 2011-07-14 2013-01-16 上海一诺仪表有限公司 Cone-shaped ultra-waveguide vibrator of ultrasonic transducer
US8553894B2 (en) 2010-08-12 2013-10-08 Bose Corporation Active and passive directional acoustic radiating
US9451355B1 (en) 2015-03-31 2016-09-20 Bose Corporation Directional acoustic device
US10057701B2 (en) 2015-03-31 2018-08-21 Bose Corporation Method of manufacturing a loudspeaker

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3750838A (en) * 1971-11-29 1973-08-07 J Pyle Concrete resonant cone speaker system
US4206831A (en) * 1976-03-29 1980-06-10 Robert B. Welch Loudspeaker coupler
US4650031A (en) * 1985-06-15 1987-03-17 Bose Corporation Cabinet for loudspeaker
US4991688A (en) * 1989-05-02 1991-02-12 Ervin Kery Audio speaker system
US5266752A (en) * 1992-12-14 1993-11-30 Cussans Rick C Reflex folded horn speaker enclosure

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3750838A (en) * 1971-11-29 1973-08-07 J Pyle Concrete resonant cone speaker system
US4206831A (en) * 1976-03-29 1980-06-10 Robert B. Welch Loudspeaker coupler
US4650031A (en) * 1985-06-15 1987-03-17 Bose Corporation Cabinet for loudspeaker
US4991688A (en) * 1989-05-02 1991-02-12 Ervin Kery Audio speaker system
US5266752A (en) * 1992-12-14 1993-11-30 Cussans Rick C Reflex folded horn speaker enclosure

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN, Vol. 9, No. 189, E-333; & JP,A,60 057 798 (YUUJI KAMIJIYOU), 3 April 1985. *

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101026895B (en) * 1998-09-03 2014-01-29 伯斯有限公司 Waveguide electracoustical transducer
EP0984662A3 (en) * 1998-09-03 2001-04-11 Bose Corporation Waveguide electroacoustical transducing
EP1284585A1 (en) * 1998-09-03 2003-02-19 Bose Corporation Waveguide electracoustical transducing
US6771787B1 (en) 1998-09-03 2004-08-03 Bose Corporation Waveguide electroacoustical transducing
CN101026895A (en) * 1998-09-03 2007-08-29 伯斯有限公司 Waveguide electracoustical transducing
US7623670B2 (en) 1998-09-03 2009-11-24 Jeffrey Hoefler Waveguide electroacoustical transducing
EP0984662A2 (en) * 1998-09-03 2000-03-08 Bose Corporation Waveguide electroacoustical transducing
FR2828784A1 (en) * 2001-08-17 2003-02-21 Etienne Bardier Loudspeaker homogeneous bass sound transmission having guide tube axially placed loudspeaker membrane with surface around tube with structure enclosure held.
EP2218266A1 (en) * 2007-11-09 2010-08-18 Koninklijke Philips Electronics N.V. Alert device and method
US8295526B2 (en) 2008-02-21 2012-10-23 Bose Corporation Low frequency enclosure for video display devices
US8351629B2 (en) 2008-02-21 2013-01-08 Robert Preston Parker Waveguide electroacoustical transducing
US8351630B2 (en) 2008-05-02 2013-01-08 Bose Corporation Passive directional acoustical radiating
US8265310B2 (en) 2010-03-03 2012-09-11 Bose Corporation Multi-element directional acoustic arrays
US8553894B2 (en) 2010-08-12 2013-10-08 Bose Corporation Active and passive directional acoustic radiating
CN102883252A (en) * 2011-07-14 2013-01-16 上海一诺仪表有限公司 Cone-shaped ultra-waveguide vibrator of ultrasonic transducer
US9451355B1 (en) 2015-03-31 2016-09-20 Bose Corporation Directional acoustic device
US10057701B2 (en) 2015-03-31 2018-08-21 Bose Corporation Method of manufacturing a loudspeaker

Also Published As

Publication number Publication date
AU3604495A (en) 1996-05-02
DK171338B1 (en) 1996-09-09
DK117494A (en) 1996-04-11

Similar Documents

Publication Publication Date Title
US7138576B2 (en) Sound system and method for creating a sound event based on a modeled sound field
RU2325789C2 (en) Speaker assembly with specifically shaped sound field
KR920003265B1 (en) Defined coverage loud speaker horn
CN103782610B (en) Acoustic horn is arranged
CN104538023B (en) Acoustic diffusion generator
CN1235688A (en) Cone reflector/coupler speaker system and method
WO1996011558A1 (en) Omnidirectional sound source
CN102907115A (en) Coaxial speaker system having a compression chamber with a horn
JPH07312792A (en) Ceiling loudspeaker
Eargle Electroacoustical reference data
US5659155A (en) Acoustical transducer enclosure
JP2006502657A (en) Sound reproduction device with improved directivity
EP1889510B1 (en) Sound reproduction with improved performance characteristics
CN102595282A (en) Method and system for integrating multimedia audio-visual device
US7142680B2 (en) Multiple waveguide coaxial ceiling loudspeaker
Martellotta Optimizing stepwise rotation of dodecahedron sound source to improve the accuracy of room acoustic measures
US8670585B2 (en) Spherical sound source for acoustic measurements
US6068080A (en) Apparatus for the redistribution of acoustic energy
Capel Newnes Audio and Hi-fi Engineer's Pocket Book
Martin Directivity and the acoustic spectra of brass wind instruments
US6435301B1 (en) Apparatus for the redistriabution of acoustic energy
Misdariis et al. Radiation control on a multi-loudspeaker device
KR100519052B1 (en) Multiple speaker system for generation of bright and dark sound zones and method thereof
CN209823946U (en) Acoustic sound gathering sound box with high-frequency reflection cone and low-frequency phase-reversing hole structure
Otondo et al. Directivity of musical instruments in a real performance situation

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): AL AM AT AT AU BB BG BR BY CA CH CN CZ CZ DE DE DK DK EE EE ES FI FI GB GE HU IS JP KE KG KP KR KZ LK LR LT LU LV MD MG MK MN MW MX NO NZ PL PT RO RU SD SE SG SI SK SK TJ TM TT UA UG US UZ VN

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): KE MW SD SZ UG AT BE CH DE DK ES FR GB GR IE IT LU MC NL PT SE BF BJ CF CG CI CM GA GN ML MR NE SN TD TG

DFPE Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101)
121 Ep: the epo has been informed by wipo that ep was designated in this application
REG Reference to national code

Ref country code: DE

Ref legal event code: 8642

122 Ep: pct application non-entry in european phase
NENP Non-entry into the national phase

Ref country code: CA