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
  • H04R1/22—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only 
  • H04R1/28—Transducer mountings or enclosures modified by provision of mechanical or acoustic impedances, e.g. resonator, damping means
  • H04R1/2803—Transducer mountings or enclosures modified by provision of mechanical or acoustic impedances, e.g. resonator, damping means for loudspeaker transducers

Definitions

• the present invention relates to a loudspeaker arrangement.
• a loudspeaker generally comprises a membrane in connection with a magnet and a coil, which are mounted to a basket provided with outlet holes behind the membrane.
• the loudspeaker is arranged in an enclosure with the membrane side facing outwards .
• the motion of the membrane of the loudspeaker is affected by the compliance of the enclosed air.
• the compliance varies with frequency and is dependent on resonances and standing waves in the enclosed air and vibrations in the enclosure itself.
• a soft absorbing material such as mineral wool, plastic foams and felt.
• US 4 278 852 A shows an earphone construction with a special loudspeaker that produce an impression that the acoustic event reaches the ear from the outside.
• a sound absorbing cover is provided that reduces middle and high frequencies, mostly 1 kHz to 12 kHz. Sound of frequencies below, i.e. low frequency sound is hardly damped but pass through the porous material.
• US 5 504 281 A shows perforated acoustical attenuators made of a porous material comprised of particles sintered and/or bonded together at their points of contact and having through holes provided therein. The material could be a polymeric material.
• the perforated attenuator of the invention provides sufficient ventilation while still providing a high level of sound attenuation. Therefore, the attenuator is good as acoustical barrier in office equipment such as computers and photocopiers.
• the air flow through the holes is important for the ventilation of the apparatuses in such attenuators . Because of the holes the sound absorbing of low frequncies are poor.
• the problem is to provide a loudspeaker arrangement that is efficient in sound absorbation at low frequencies .
• the separation of the air space at the back of the membrane from the ambient air with a sintered polymeric porous material an efficient damping of the low frequencies will be achieved and the damped sound pressure will be delayed in its progress to ambient air, since the porosity of the sintered polymeric porous material -allow the air to in a delayed way pass through the separating "wall", causing a damping of the sound.
• the sintered polymeric porous material functions as an impedance for the air waves and provide longer ways for the air to pass until it reaches the ambient air.
• echoes, standing waves and resonances in a loudspeaker enclosure, in its structures or in ambient air are in this way separated from the air behind the membrane and will thus be damped, too, so that the influence on the membrane is minimized.
• An advantage of this invention is that the size of the loudspeaker arrangement can be minimized since such an efficient damping is performed directly behind the membrane, only leaving a small air space between absorbent and membrane.
• Another advantage of this invention is that the demand for stiffness of loudspeaker boxes will be lower.
• a further advantage of this invention is that the sound pressure in an enclosure of a loudspeaker will be lower and consequently cause less vibrations in the structur .
• a still further advantage of this invention is that it will be easy to implement in production lines since a robot can be used for mounting the absorbent due to its stability. This is difficult with soft absorbent.
• Fig. 1 illustrates a first embodiment of an acoustical absorbent of the present invention from behind and a typical loudspeaker.
• Fig. 2 illustrates the front of the typical loudspeaker in fig. 1 showing the membrane.
• Fig. 3 illustrates the first embodiment of the acoustical absorbent of the present invention showing the front of the typical loudspeaker without the membrane.
• Fig. 4 illustrates the first embodiment of the acoustical absorbent assembled with the loudspeaker forming a loudspeaker arrangement.
• Fig. 5 illustrates a second embodiment of an acoustical absorbent of the present invention from behind and a typical loudspeaker.
• Fig. 6 illustrates the second embodiment of the acoustical absorbent assembled with the loudspeaker forming a loudspeaker arrangement.
• Fig. 7 illustrates the front of a third embodiment of an acoustical absorbent of the present invention together with a loudspeaker forming a loudspeaker arrangement .
• Fig. 8 illustrates the third embodiment of the acoustical absorbent assembled with the loudspeaker from behind.
• an acoustical absorbent 1 according to the present invention is illustrated which is designed to fit into the back of a typical loudspeaker 2, see fig. 2.
• the loudspeaker 2 comprises a magnet 3, a membrane 4 and a basket 5 in which the membrane 4 and the magnet 3 are provided.
• the basket 5 is provided with holes 7 through which the moving air behind the membrane 4 pass.
• the acoustical absorbent 1 have protrusions 6 that are designed to snuggly fit into the holes 7 to cover and fill the holes 7 up fully with the acoustical absorbent 1.
• the acoustical absorbent 1 may be attached by an adhesive or by frictional forces to the loudspeaker basket 5, for example. It is important for the absorbing of low frequencies that no through holes or openings are present, through which sound, i.e. air waves, may freely pass. Instead the air waves should be delayed and attenuated through the sintered polymeric porous material .
• a loudspeaker arrangement 8 is illustrated where the acoustical absorbent 1 is attached to the back of a loudspeaker basket 5.
• a second embodiment of the acoustical absorbent 1 is illustrated.
• the acoustical absorbent 1 is designed like a cup or cover 9 that is to be attached over the back of the loudspeaker 2 to cover the holes 7 in the basket 5 of the loudspeaker 2.
• cup 9 may be attached by adhesive, staples or be clamped or screwed thereon.
• a third embodiment of the acoustical absorbent 1 is illustrated.
• the acoustical absorbent 1 also functions as a loudspeaker basket 5' .
• the basket 5' does not have any holes 7. Due to the rigidity of the sintered polymeric porous material it is possible to provide the magnet 3 and the membrane 4 in such a basket 5' .
• the basket 5' is provided with rigid inner and outer rings 10.
• the sintered polymeric porous material could, for example, be a polyethylene, preferably a high density polyethylene.
• the material may have an average pore size of 90-200 micrometer, preferably of 110-190 micrometer or most preferred, of 125-180 micrometer.
• the thickness of the material could be about 6-10 mm, but this depends upon the dynamical characteristics of the loudspeaker.
• the invention divides the air behind a loudspeaker into a small space of air situated directly behind the membrane and the ambient air by means of a "wall" of sintered polymeric porous material .
• the "wall” could comprise the basket or replace the basket or cover the basket, for example in a cup-shaped style, closely to the basket.

Landscapes

• Health & Medical Sciences (AREA)
• Otolaryngology (AREA)
• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Signal Processing (AREA)
• Diaphragms For Electromechanical Transducers (AREA)
• Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)
• Details Of Audible-Bandwidth Transducers (AREA)

Applications Claiming Priority (2)

Publications (2)

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Family Applications (1)

Country Status (2)

Cited By (1)

Citations (5)

• 2001
  • 2001-01-31 SE SE0100285A patent/SE522767C2/sv not_active IP Right Cessation
• 2002
  • 2002-01-23 WO PCT/EP2002/000642 patent/WO2002062099A1/en not_active Application Discontinuation

Patent Citations (5)

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