Classifications

• • 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
  • H04R25/65—Housing parts, e.g. shells, tips or moulds, or their manufacture
  • H04R25/652—Ear tips; Ear moulds
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B17/00—Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations
  • G01B17/06—Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations for measuring contours or curvatures
• • 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
  • H04R25/65—Housing parts, e.g. shells, tips or moulds, or their manufacture
  • H04R25/658—Manufacture of housing parts
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/103—Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
  • A61B5/107—Measuring physical dimensions, e.g. size of the entire body or parts thereof
  • A61B5/1076—Measuring physical dimensions, e.g. size of the entire body or parts thereof for measuring dimensions inside body cavities, e.g. using catheters
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
  • A61B8/12—Diagnosis using ultrasonic, sonic or infrasonic waves in body cavities or body tracts, e.g. by using catheters
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y80/00—Products made by additive manufacturing

Definitions

• This invention relates to the process of manufacturing hearing aid shells.
• Hearing aid shells are currently manufactured by making an impression of a patient's ear canal by means of injecting a liquid silicon rubber compound into the canal and allowing it to solidify. This mould is then withdrawn from the ear and sent to a laboratory where a master casting mould is made that is used to cast the patient's hearing aid shell. This process is far from ideal as the silicon rubber compound shrinks during the curing stage resulting in an imperfect mould being cast . This requires that the shell be sent back to the laboratory for shape modification, a number of times, before a proper fit can be obtained. The process is also critically dependent on the skill of the individual hearing aid practitioner during the injection stage,resulting in a considerable variability of the accuracy of the impressions.
• This invention obviates these problems by means of the following process.
• This entails the use of a non-contacting , ultrasonic probe, that has been developed for arterial imaging, and that images the shape of the ear canal cavity and relays this information to an image processing computer where a digital image file of the ear canal's shape is created.
• This file is then used in conjunction with a rapid prototyping setup such as stereo lithography, selective laser sintering , laminated object modelling , inkjet modelling , fused deposition modelling, 3DP the three dimensional printing system of the Massachusetts Institute of Technology, and any other rapid prototyping system that produces real models from computer mathematical models to manufacture the hearing aid shell that accurately fits the ear canal.
• Figure 1 shows a block diagram of the process where the electrical signal that contains the shape information from the ultrasonic probe (1) is fed into the image processing computer (2) that also incorporates the control electronics that generate the appropriate signals for the transmission and reception of the ultrasonic signals required for the operation of the probe .
• processing and enhancement that includes the use of an edge detection algorithm that detects the boundary between the ear canal wall and the liquid used for acoustically coupling the ultrasonic waves from the transducer to the wall ,multiple cross-sectional views of the ear canal can be viewed and manipulated on a monitor. Edge detection is necessary as the ultrasonic waves give reflected signals over a range of different depths of the wall's thickness.
• a digital image file of the shape of the ear canal is then transmitted directly to a rapid prototyping system (4) or recorded onto a compact disc (3) that is used in a rapid prototyping system (4) to produce an accurate hearing aid shell (5).
• Figure 2 shows the location of the ultrasonic probe (6) in the ear canal (7) .
• multiple transmitter/receiver transducers (8) positioned around the circumference of the probe sequentially record the cross-sectional shape of the canal acting like minature pulsed radar systems. This measurement is repeated for adjacent sections of the canal by means of a stepper motor controlled actuator (9) that withdraws the probe incrementally from the canal until the required area has been measured.
• the accuracy along the longitudinal axis of the ear canal depends on the size of each increment , 1 to 3 mm. being typical values.
• FIG 3 shows an embodiment of the ultrasonic probe head (10) where a coherent fibre optic bundle (11) is incorporated into the central region of the probe to allow the practitioner to determine a safe position of the head of the probe with respect to the tympanic membrane ,(ear drum ), (12), the image being viewed on a separate monitor. Illumination of the ear drum is accomplished by means of an incoherent fibre optic bundle , (15) wound around the coherent imaging fibre , (11).
• the ultrasonic transducer array (13) is wound around the coherent optical fibre (11) and the incoherent fibre (15)
• Figure 4 shows how the ultrasonic probe (14) can be positioned correctly so that it does not come into contact with the ear canal during the measurement, by means of a guiding tube (15) located in a rubber ball (16) that is placed at the entrance to the patient's ear (17) .
• the diagram also illustrates how the patient must lie on his side during the measurement as his ear canal must be filled with a liquid e.g. a saline solution (18) in order to ensure a good transmission efficiency of the ultrasonic waves from the probe to the wall of the ear canal (7) and back.
• a liquid e.g. a saline solution (18)
• Figure 5 shows a variation of the ultrasonic probe (19) that has a plastic tip (20) located at the end of the probe (21) to allow it to rest gently against a protective cover (22) that prevents the ear drum (23) from being damaged by the end of the probe (21).
• the measurement process with this probe is exactly the same as that used for the fibre optic/ultrasonic probe described in Figure 3 .
• Figure 6 shows another embodiment of the ultrasonic probe (24) that has a single or an array of the ultrasonic transducers (25) positioned at the end of the probe in order that they can measure the distance from the ear drum (23) to the end of the probe (21) as well as the circumferential array of transducers (8) that measure the cross-sectional shape of the wall of the ear canal (7) as shown in figure 2.
• This measurement is displayed on a monitor's screen to allow the practitioner to position the end of the probe (21) at a safe distance in front of the ear drum (23).
• An audible and or a visible warning can be incorporated into the system to alert the practitioner whenever the end of the probe (21) gets dangerously close to the ear drum (23)
• FIG 7 shows another embodiment of the ultrasonic probe where the ultrasonic transducers (26) are positioned along the body of the probe in a series of rings , each ring consisting of a number of transducers that measure the cross-sectional shape of the ear canal at a particular location. Each ring provides a measure of the ear canal's shape at a pre-determined position along an axis normal to the ear drum.
• This probe allows the measurement of the whole area of the inner surface of the ear canal without moving the probe during the measurement process .
• the resolution of this probe is governed by the number of transducers positioned around the periphery of each ring and the spacing of the transducer's rings along the body of the probe (27).

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Physics & Mathematics (AREA)
• Health & Medical Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Neurosurgery (AREA)
• Otolaryngology (AREA)
• Acoustics & Sound (AREA)
• Signal Processing (AREA)
• General Physics & Mathematics (AREA)
• Ultra Sonic Daignosis Equipment (AREA)

Applications Claiming Priority (9)

Publications (1)

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Country Status (4)

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• 1999
  • 1999-12-06 EP EP99958399A patent/EP1058594A2/de not_active Withdrawn
  • 1999-12-06 WO PCT/GB1999/004102 patent/WO2000034739A2/en not_active Application Discontinuation
  • 1999-12-06 AU AU15772/00A patent/AU1577200A/en not_active Abandoned
  • 1999-12-10 GB GB9929197A patent/GB2348705A/en not_active Withdrawn

Non-Patent Citations (1)

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