Application notes

Number Title Description Downloads
AN-01 Transducer Signal Port Location Key

Provides key to Knowles' port location and terminal location naming system for all microphones and receivers. Numerous examples of various port locations are provided.

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(153.12 kB)

AN-02 Direct mounting considerations for FG series cylindrical microphone

Mounting guidelines for attaching the FG microphone directly to the hearing aid faceplate. Also provides vibration sensitivity comparison of FG microphone versus other Knowles microphones.

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(79.35 kB)

AN-03 The measurement and suppression of RF interference from TDMA phones

How can cellular phones or other RF signals interfere with microphone and hearing aid operation? Examines various telecommunications protocols (TDMA, CDMA, GSM, USDC, DECT) and various frequencies (900MHz, 1.8GHz, 2.4GHz) impact on microphone performance and discusses how EMI gets into the signal path. Presents solutions on reducing RFI and EMI by using Knowles "C" and "CX" microphone technology.

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(109.42 kB)

AN-04 Directional microphone applications

Overview of directional microphones for hearing aids. Examines different microphone polar responses (omnidirectional, cardioid, supercardioid, hypercardioid) and there uses and impact on hearing aid directivity. Includes design discussion of AI-DI (articulation index weighted directivity index) and real-world applications including KEMAR and in-situ measurements.

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(242.84 kB)

AN-06 Ferrofluid damped ED receivers

Application and designers' guide to using ferrofluid damped receivers. Discusses damping level for current drive (CI) and voltage drive (CV) applications, damping options, ITE aid and BTE aid frequency reponse, temperature performance, improved shock performance, distortion performance, and multiple damping techniques (Type I screen damping, Type II damping, Type III multipierce diaphragm damping, and ferrofluid damping)

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(523.08 kB)

AN-07 Ferrofluid damped receiver part numbering system

Details the part numbering nomenclature used for specifying ferrofluid receivers, including series definition, based model numbers, the specific -i02, -i04, and -i06 suffices used for calling out the amount of ferrofluid damping, and laser marking used on the receivers themselves. Numerous examples of complete model numbers and laser markings are included

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(91.94 kB)

AN-08 HC series high-output receivers

Application and designers' guide to understanding and using the HC series High-Output receiver. Covers design basis, comparies HC series performance to FC receivers, ED receivers, and Microtronic 2600 receivers for nominal response, maximum power output (MPO), efficiency, distortion, and square wave repsonses. Details acoustic tubing, coil impedance, and damping impacts of HC receiver response and performance.

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(174.84 kB)

AN-09 Thin Mic family microphones

Examines performance aspects and applications for the Thin Mic family including the TO Thin Omni, TD Thin Directional, and TP Thin Pair microphones. Front-volume and rear-volume mutual loading impact on frequency response and directionality is exaimined along with mounting considerations and external tubing needs for maximizing directivity.

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(895.47 kB)

AN-10 Transducer warranty date code numbering system

Knowles Electronics system nomenclature for laser-marking manufacturing date codes with week and year of manufacture and warranty period is detailed. Warranty extension markings are reviewed along with numerous examples of date code markings.

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(181.16 kB)

AN-11 VEF Vibration Isolation receivers

The can-within-a-can design of the VEF receiver is examined along with specific mounting suggestions for minimizing vibration response. Design theory and test measurement systems are reviewed along with performance aspects of the VEF's rubber suspension systems. Specifc application guides for magnetic radiation (mag rad) reduction, coil changes, damping changes, terminal pad location, and port location are given.

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(155.74 kB)

AN-13 Lead-Free Soldering to Hearing Aid Transducers
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(1.89 MB)

AN-14 Marking of Microphone Pairs
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(126.97 kB)

AN-16 A Passive Current Source for Two-Wire Microphones
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(155.37 kB)

AN-17 Ultrasonic Applications for Knowles Electret and MEMS Microphones

While in most cases Knowles microphones are used for receiving audible signals, several models are also used at ultrasonic frequencies. Typical applications include animal detection (bats, rodents, insects), condition monitoring in machinery, non-contact position measurement, gesture detection, and gunshot detection / triangulation. To assist in choosing a Knowles microphone for ultrasonic applications, four models are characterized up to 100KHz.

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(625.60 kB)