Technical bulletins

Number Title Description Downloads
TB-01 Stability of amplifier systems connected to the BL microphone

Discussion of amplifier stability with regards to bias voltage, regulation, and power requirements. Both odd-numbered stage amplifiers and even-numbered stage amplifiers are examined

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(336.38 kB)

TB-02 Receiver Testing: Maximum current modulation (MCM)

Testing of DC-biased receivers for receiver response and distortion under real-life scenarios using a more accurate test method

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(502.25 kB)

TB-03 Effects of sound inlet variations on microphone response

The impact of various sound inlet tubing is discussed, including tubing diameter, length, and acoustic resistance impact on microphone reponse peak frequency, high frequency sensitivity, and overall microphone sensitivity.

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(440.55 kB)

TB-04 Soldering transducer leads

Recommended procedures and process parameters for prepping and soldering to Knowles Electronics transducers. Details on terminal construction, external leads, soldering iron, solder, flux, fixtures, and tools physical requirements are presented along with lead soldering and lead removal methods.

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(1.08 MB)

TB-05 Walk induced head vibrations and hearing aid design

Review of various sources of human body movement induced vibration that impact hearing aid performance, including "head thumps", "walk acceleration", and other physical motions that hearing aids interpret as spurious acoustic signals.

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(608.74 kB)

TB-06 Effects of acoustical termination upon receiver response

External tubing can greatly impact a receivers response curve. Varying the tubing length, varying the tubing diameter, using combinations of different tubing lengths/diameter, and adding acoustic dampers can all have a marked impact on receiver output.

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(413.30 kB)

TB-07 Effects of source impedance upon receiver response

The impedance of the signal source with respect to the receiver's impedance can affect the shape of the response curve. The impact of source impedance vs. receiver impedance matching is presented for constant current, constant voltage, and maximum available power drives.

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(206.17 kB)

TB-08 The transducer environment

Protocols for transducer handling, holding fixtures, soldering, contaminants, ESD, temperature, humidity, radiation, and pressure changes are listed. Also, application guidelines and recommendations for shock and vibration, contaminants, ESD, temperature, humidity, radiation, and pressure are detailed.

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(114.00 kB)

TB-09 BT condenser microphone 2-wire application notes

Design guides and application notes for using the BT microphone with 2-wire driver/pre-amp circuitry. Numerous sample circuits and examples are presented.

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(304.92 kB)

TB-10 BW-1789 application notes

Application guidelines and design notes for critical areas of using the BW-1789 close talking microphone are reviewed. A special section on packaging the BW-1789 for close-talking applications is included.

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(142.05 kB)

TB-11 Effectrs of variation of supply voltage on the sensitivity of the BL microphone

The impact on BL microphone sensitivity by using supply voltages from 0.9VDC to 20.0VDC is discussed.

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(137.74 kB)

TB-12 Application notes for BL series microphones

General design guidelines and application suggestions for the BL series microphones including 3-wire and 2-wire pre-amp/driver circuits and the reduction of power supply ripple voltage.

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(158.10 kB)

TB-13 Effects of variation of the supply voltage on the sensitivity of the BT microphone

The impact on BT microphone sensitivity by using supply voltages in the 0.4VDC to 1.3VDC range and the 1.3VDC to 20.0VDC range are discussed.

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(121.60 kB)

TB-14 The effect of acoustic damping plugs on receiver response

Use of the BF series dampers to smooth receiver response curve resonance peaks for CI, EF, ED, and EH series receivers. Impact of various amounts of acoustic resistance, difference damper styles, different damper diameters, and different damper positioning is examined via numerous examples.

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(423.93 kB)

TB-15 XL-9073 probe microphone kit application notes

Overview of the Knowles probe microphone kit for acoustic test measurements. Included are driver circuit examples and comments on various application scenarios.

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(115.38 kB)

TB-16 Electronics response shaping of directional microphones

The use of analog RC filter networks to shape the low-frequency and high-frequency responses of Knowles directional microphones. Also includes implementation suggestions on the equalization of Knowles microphones in directional applications.

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(182.96 kB)

TB-17 Broader band BK application notes

Various impacts on broader-band BK receiver response as tubing length, tubing diameter, tubing material, cavity size, coupler type, and drive source are varied.

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(374.74 kB)

TB-18 CB application notes

Output response of the CB speaker for various acoustic loads, drive conditions, and power envelopes are discussed. Also, the ability for the CB speaker to operate in reverse mode as a microphone is studied.

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(327.99 kB)

TB-19 Vibration sensitivity of Knowles microphones

Vibrations to Knowles microphones is interpretted as spurious acoustic signals. The vibration sensitivities and vibration induced acoustic responses for the BT, EA, EK, EG, and EM microphones are presented.

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(121.00 kB)

TB-20 Wideband receiver application bulletin

Several examples of extending the ED and BP receiver frequency response via different acoustic tubing constructions are reviewed. Included are physical devices layouts and frequency response comparison curves.

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(208.25 kB)

TB-21 EB directional hearing aid microphone application notes

Overview of EB series directional microphones along with a definition of directional mic terminology, the impact of port resistances and rear-port delays. Four major design goals of the EB microphone - sensitivity, frequency response curve shape, polar pattern response, and signal-to-noise performance - are examined in detail.

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(1.08 MB)

TB-22 Magnetic leakage for receivers

Examination of magnetic radiation (mag rad) phenomina for BK, BP, ED, and EF series receivers. Mag rad field amplitude, field orientation, and critical frequencies are discussed.

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(182.75 kB)

TB-23 Mounting application notes

General transducer physical mounting suggestions for antishock mounting, soldering, and acoustic transmission are reviewed.

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(228.26 kB)

TB-24 ESD and low frequency voltage noise related issues to the Improved EM microphone

The impact of electrostatic discharge (ESD) on Improved EM series microphones. Specific recommendations for microhpone handling, ESD protection, and manufacturing facility grounding are given. Also discussed is the low-frequency oscillation produced by the Improved EM microphones internal FET impedance converter circuitry.

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(105.11 kB)

TB-25 Improved EM microphone

Features and benefits of the Improved EM microphone series including sensitivity improvements, equivalent noise pressure (ENP noise), one-third octave noise, and power supply feedthrough attenuation (PFA) are each examined in detail.

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(290.99 kB)