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
  • H04R1/40—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only by combining a number of identical transducers
  • H04R1/406—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only by combining a number of identical transducers microphones
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R2201/00—Details of transducers, loudspeakers or microphones covered by H04R1/00 but not provided for in any of its subgroups
  • H04R2201/40—Details of arrangements for obtaining desired directional characteristic by combining a number of identical transducers covered by H04R1/40 but not provided for in any of its subgroups
  • H04R2201/401—2D or 3D arrays of transducers
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R2410/00—Microphones
  • H04R2410/07—Mechanical or electrical reduction of wind noise generated by wind passing a microphone
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R25/00—Deaf-aid sets, i.e. electro-acoustic or electro-mechanical hearing aids; Electric tinnitus maskers providing an auditory perception
  • H04R25/40—Arrangements for obtaining a desired directivity characteristic
  • H04R25/405—Arrangements for obtaining a desired directivity characteristic by combining a plurality of transducers

Definitions

• the present invention relates to use of electro-acoustic transducers and more particularly to an arrangement in conjunction with an electronic circuit which reduces the effects of wind noise in the case of a microphone.
• the present invention provides an electro-acoustic transducer arrangement comprising three or more bi-directional transducer elements disposed at an angle to each other in three dimensions and pointing generally towards a common sound source. The outputs of the elements are added together to provide an output signal with increased signal to noise ratio.
• An advantage of the present invention is that there is no requirement for there to be a desired sound source present for the invention to work.
• Fig 1 shows diagrammatically a first embodiment of microphone in accordance with the present invention
• Fig 2 shows a block diagram of a circuit for use with the microphone of Fig 1 ;
• Fig 3 shows diagrammatically two dimensional relative angles between microphones for explanatory purposes
• Fig 4 shows a block diagram of a further arrangement including modified circuitry according to the present invention.
• Embodiments of the present invention comprise at least three bi-directional transducer elements.
• a bi-directional transducer element is one where there are front and rear ports in a housing with the diaphragm of the transducer disposed within the housing so as to be influenced by sound waves entering the housing through the front and rear ports.
• the elements are ideally positioned relative to each other such that their front ports are equidistant from a desired source and a projection of the central axis of each element forms a unique angle at the back port.
• the elements can be located on the surface of an imaginary sphere so that they are all equidistant from the desired sound source.
• the sensitivities of the front ports of the bidirectional microphones overlap as much as possible and the sensitivities of the rear ports overlap as little as possible as indicated in fig. 3.
• the desired sound source is located generally in the overlap of the front ports to where the most gain will be achieved.
• the wind noise rejection effect is not significantly affected by the direction that the wind is blowing.
• the desired sound is usually located generally in front of the front ports, though this is not critical.
• the microphones shall not be mounted in a physical hemispherical or parabolic device normally used to focus the desired sound to a common focus because this will create unacceptable differences in wind pressure on the front and back ports which will adversely reduce the wind noise rejection.
• the axis of each may correspond to the perpendicular axis of each dimension of three dimensional space (X 5 Y 5 Z) and therefore rio two microphones share a common axis angle.
• the microphones can be mounted in an enclosed container and exposed through a common hole. Furthermore, the microphones should be shielded from the wind with a thin acoustic resistive material that may surround them or at least placed over the exposed hole(s) common to all microphones. This material can be thin felt or acoustic foam similar to that used to cover the ear pieces of headphones. This will now be explained in more detail in relation to the transducer element being a microphone element.
• a bi-directional microphone element has the same sensitivity front and back and will produce an electric signal as a result of the difference of the sound pressure entering the front and back ports of the element.
• the B and D elements in Fig 1 are physically disposed in the same plane but the axes of the elements B and D pointing generally at a zone containing the sound source.
• the axes of the two elements are in the same plane but at different angles.
• the middle element C is physically above the plane as the elements B and D but it is tilted. Thus, it is pointing at the zone containing the sound source but with its front polar response diagram substantially overlapping those of the elements B and D. Consequently, the advantages of the present invention can be obtained with this arrangement.
• Fig 2 it will be seen that with this arrangement of microphone elements, it is possible to arithmetically add the outputs of all the microphone elements.
• the electrical outputs can be added together in any convenient manner using any suitable analogue or digital procedure such as digital signal processing.
• the preferred embodiment utilises three bi-directional microphones, three, or more microphone elements may be used.
• the elements are bi- directional. Consequently, each element's performance can be represented by front and back polar response diagrams centered around an axis. In the ideal situation where the elements are equidistant from a desired sound source, the front polar response diagrams will overlap to a considerable degree.
• the rear polar response diagrams ideally should not overlap and the microphone elements are disposed relative to each other to achieve this.
• the overlap of the sensitivity diagrams is a factor to this limit of the number of microphone elements.
• the front ports ie those closest to the desired sound source.
• the microphone elements such that their central axes will ideally coincide with the focus of the geometric surface on which they are theoretically disposed, all that is required, in practice, is that there is substantial overlap of the front facing polar sensitivity diagrams of the elements.
• the polar sensitivity diagram represents a three-dimensional space, as long as the desired sound emanates from the volume contained by the overlapping portions of the respective polar diagrams, the advantages of the present invention will be achieved. It is thus also apparent that strict equidistance is not required. A large degree of difference can be accommodated, defining a zone or volume.
• the bi-directional elements are located within a housing provided with or formed by a layer of acoustic resistant material.
• the bi-directional elements may be located in a case with one or more holes, in which case only the holes need be covered with a layer of acoustic resistive material.
• this material may be of a very thin variety such as that normally associated with headphones and therefore not burden the practical manufacturability of the invention.
• both the front and back ports are open with the rear ports acoustically exposed so that the axes extend through the front and back ports away from the element in free space.
• the above embodiment discloses the use of microphone elements disposed on the surface of an imaginary sphere, it is also possible to locate the microphone elements on the imaginary surface of any other geometric figure which has a focus.
• the elements can be disposed as a matrix or cruciform shape (a three dimensional array) or as depicted in Fig 1.
• the microphone elements will be mounted in some manner so that the three dimensional array is in a relatively fixed position with respect to the desired sound source.
• the microphone could be attached to the end of a boom which itself is part of an ear piece or headset.
• the microphone could be mounted in a helmet which may have an oxygen feed acting as an internal source of unwanted wind noise, or it could be used to replace the existing microphone in existing outside broadcast arrangements where the microphone is located within a cage which is arranged to be held against the face of a user with the microphone itself spaced from the user's mouth by a distance.
• Applications include wired or Bluetooth PHF (Personal Hands Free) for use with a mobile phone.
• the microphone may be used with a digital or video camera such that the desired sound is coming from approximately in front of the camera. The people speaking may be non- stationary or moving without affecting the desired affect wind noise rejection.
• Fig. 1 is useful to explain an optional modification which can be made to the circuitry which is fed by the microphone arrangement.
• the wind direction is represented by the arrows in Fig 1 and it will be seen that the microphone element B has its axis lying normal to the wind direction.
• Fig 4 shows a block diagram of a microphone array with electronic circuitry for carrying out the inhibition and signal processing mentioned above. There are many other methods for achieving this using either analog or digital solutions.
• the microphone elements B,C and D are shown covered by a common thin layer of acoustic resistive foam material 50.
• the outputs of the elements are fed to a selector circuit 51 where the signals are compared and the signal from the worst affected element is inhibited. Thereafter, the signals are fed through level and frequency control circuits 52, signal conditioning circuits 53 and then added together and fed to an output 55 after processing in a filter circuit 54 which applies band pass filtering below 200Hz. Other notch and band pass filtering can be provided to compensate for slight low frequency drop off in the voice frequency band.
• the array of microphone elements replaces a conventional microphone and thus can be used as a direct replacement for such a microphone by being incorporated into equipment during manufacture. This may be achieved by incorporating the microphone elements and the associated signal addition circuitry as components of the larger equipment during manufacture.
• the microphone elements could be packaged in such convenient manner with or without their associated signal addition circuitry and provided to manufacturers as a module.
• the microphone elements may be mounted at the appropriate angle to each other and in the correct orientation by use of an over-molded high temperature polymer. Care has to be taken to ensure that the rear ports are unobstructed and that the front to back port wind pressure is minimally affected by the mounting structure.
• the mounting structure should minimize the effect of altering the direction of the wind as picked up by the one microphone with respect to the others. In other words, all microphones should detect the wind coming from the same general direction.
• the array of bi-directional transducer elements may be mounted in a housing which may be waterproof but is provided with an array of perforations covered by a thin layer of acoustic resistive material.
• the housing may be provided with means for attaching the array of elements to another piece of equipment on a user, e.g. by means of a spring clip.
• the present invention has wide application either as component parts of a larger piece of equipment or as a module for the larger equipment. To give some indication of the various applications, a number of different implementation will now be described. This is not an exhaustive list.
• One implementation is to replace an outside broadcast microphone as indicated previously. Another is to replace the microphone in a mobile phone or part of a personal hands-free kit for a mobile phone. Another is to replace the microphone in portable recording devices.
• a further implementation is to replace the microphone in a digital camera or video camera, video camera-phone, or another portable communication device.
• This can be either the microphone which is pointed at the user so that the user can comment on the scene being photographed.
• the transducer is normally termed a hydrophone.
• the bidirectional transducer elements can be fabricated using semiconductor techniques which allows the array of elements to occupy very little space.
• a MEMs microphone sometimes referred to as a SiMIC (Silicon Microphone) will require the addition of a rear aperture or apertures to enable bi-directionality.
• miniature bidirectional microphone elements in an appropriate array permits a version of the invention to be utilised in a hearing aid that is suitable for use outdoors and in brez or windy conditions.
• uni-directional microphone elements can also be used as they also exhibit the same properties and effects but to a much lesser degree.

Landscapes

• Health & Medical Sciences (AREA)
• Otolaryngology (AREA)
• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Signal Processing (AREA)
• Circuit For Audible Band Transducer (AREA)
• Transducers For Ultrasonic Waves (AREA)
• Obtaining Desirable Characteristics In Audible-Bandwidth Transducers (AREA)
• Motor Or Generator Cooling System (AREA)

Applications Claiming Priority (3)

Publications (2)

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Family Applications (1)

Country Status (4)

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• 2006
  • 2006-03-30 DE DE602006012030T patent/DE602006012030D1/de active Active
  • 2006-03-30 EP EP06726572A patent/EP1872619B1/fr not_active Not-in-force
  • 2006-03-30 AT AT06726572T patent/ATE456906T1/de not_active IP Right Cessation
  • 2006-03-30 WO PCT/GB2006/001166 patent/WO2006103441A1/fr active Application Filing

Non-Patent Citations (1)

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