Presentation on theme: "2 nd International Hearing Loop Conference: Telecoil Panel Linda Kozma-Spytek Research Audiologist Technology Access Program Gallaudet University RERC."— Presentation transcript:
2 nd International Hearing Loop Conference: Telecoil Panel Linda Kozma-Spytek Research Audiologist Technology Access Program Gallaudet University RERC - Telecommunications Access RERC – Hearing Enhancement
passive amplified Photo used with permission from Oticon, Inc. Sensitivity is determined by its: size and geometry programming gain (amplification) applied Amplified Telecoils consist of a coil and preamplifier preamp increases sensitivity of the telecoil should have RF-interference protection Telecoils A telecoil is a coil of wire around a magnetic metal core that is sensitive to magnetic fields. Approximately 60% of hearing aid fittings in the US include a telecoil, and all cochlear implants have telecoils.
Telephones (directly) Landline Phones (corded and cordless) Wireless Devices (basic cell phones, feature phones and smart phones) Hearing Assistive Technology (HAT) Induction Loop Systems (directly) Other HATs (FM/IR) via Neckloops Silhouettes Headsets Audio Devices (telephones, music players, etc.) via Neckloops Silhouettes Headsets Telecoils are used in hearing devices to connect to:
Programming Fully programmable memory dedicated for telecoil use: amplification characteristics can be independently adjusted by the audiologist, including mixing input from the telecoil and microphone amplification characteristics can also be preset (manufacturer default telecoil program) Manual: Remote Control Touchless Telecoil Automatic:
+ Reduce acoustic background noise in all communication settings (- magnetic noise) + Reduce the effects of poor room acoustics (reverberation) in all communication settings + Reduce the effects of distance (level of the speakers voice remains constant regardless of the distance between the hearing aid wearer and the speaker) in settings where the telecoil is part of a hearing assistive technology system (- microphone location) + Eliminate acoustic feedback during telephone coupling Why use telecoil coupling?
SPEECH noise reflected sound Induction Loop (IL) System T SPEECH Acoustic Loudspeakers
Telecoil Orientation Figures adapted with permission from HyperPhysics by Rod Nave, For best coupling with a telecoil, a magnetic field should cut across all turns in the wire of the telecoil by aligning with the axis of the core. maximum coupling maximum coupling no coupling no coupling
horizontal telecoils couple best with axial (horizontal) magnetic field lines of a telephone vertical telecoils couple best with the weaker radial (vertical) magnetic field lines of a telephone vertical telecoils couple best with the vertical magnetic field lines of a room loop Magnetic Field Orientation
dB (SPL) equivalent dB (A/m) 90 0 highest axial field strength measured on cordless phone samples IEC specified speech peak field strength for induction loop systems (400 mA/m) C63.19 required minimum axial and radial field strength for wireless devices IEC resulting long-term average level of speech for induction loop systems (100 mA/m) 68 -22 [-37] RS-504 required minimum axial field strength for landline phones [in-use levels are ~15 dB lower] 63 -27 [-42] RS-504 required minimum radial field strength for landline phones [in-use levels are ~15 dB lower] 60-30lowest axial field strength measured on cordless phone samples ANSI S3.22 (1996) - HA quality assurance standard – reference for telecoil sensitivity measurement (31.6 mA/m) 50-40TIA 1083 specified A-weighted magnetic noise maximum field strength of ambient magnetic noise (A-weighted) measured in a parking lot, under power lines field strength of ambient magnetic noise (A-weighted) measured in a living room Source Magnetic Field Strengths
Receiver HA (amplified) telecoil + + Net Frequency Response HA Signal Processing = Net Frequency Response Magnetic Source Induction Loop System Telephone
Comparison of Magnetic Frequency Responses for Telephones and Audio Loops
What needs to be considered for telecoil coupling capability? Source (Magnetic) Requirements: High enough signal strength Low enough noise/distortion level High enough signal to noise ratio Usable field orientations Large enough coverage area Appropriate frequency response Receiver (Telecoil) Requirements: Adequate sensitivity Low enough noise/distortion level High enough signal to noise ratio Usable telecoil orientation Standard frequency response System Verification Goals: To objectively quantify the real-ear performance of the hearing aid in telecoil mode (when coupled to a telephone or hearing assistive technology) in relation to a prescriptive target Need: Level-controllable standard inductive signal sources
The contents of this PowerPoint presentation were developed under grants from the Department of Education, NIDRR grant numbers H133E and H133E However, the opinions and content are those of the grantees and do not necessarily represent the policy of the U.S. Department of Education. Acknowledgements