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-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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(574.54 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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(163.69 kB)

AN-13 Soldering to Knowles transducers

Aids the user in assembling Knowles transducers into finished products with good soldering reliability while avoiding heat damage.

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(418.63 kB)

AN-16 A Passive Current Source for Two-Wire Microphones

Though two-wire microphones are often powered with an active current source, in many applications a passive sourse as described can be used.

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(155.37 kB)