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Directional Microphone Models Source from Dillon H. Directional Microphone Models. Directional Mics: Old vs New. Conventional directional mics 1 mic with 2 ports often no option for turning on/off Newer directional mics can be turned on & off 2 omni mics (1 port each)
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Directional Microphone Models Source from Dillon H
Directional Mics: Old vs New • Conventional directional mics • 1 mic with 2 ports • often no option for turning on/off • Newer directional mics can be turned on & off • 2 omni mics (1 port each) • e.g. Phonak’s “Audiozoom” • 1 omni & 1 regular directional mic • e.g. Etymotic’s “Dmic”
Orders of Directional Mics • First order • single cartridge mics with 2 ports • 2 omni directional mics • Second order (Beamforming) • more than 2 mics • like a magnifying glass • not always practical at this time • may be much better used in DSP
Sounds Hitting Both Sides Cancel Each Other Out
Directional Mic Function When Sounds Come From Front
D))))) From the Front
Diaphragm moves From the Front D)))))
Sound From BehindSound is cancelled by hitting both sides of diaphragm
((((( From Behind
From Behind • ((((( (
From Behind • ((((( (
From Behind • ((((( (
From Behind • ((((( )
Diaphragm does not move From Behind • ((((( )
Directional Microphones & Client Use • Newer directional mics have several positions • omni-directional • directional equalized to omni-directional response • directional with low-cut response
Directional Microphones & Client Use 60 white line: omni mic dotted line: directional mic (low cut is common) 50 40 30 Gain in dB 20 10 0 -10 250 500 1k 2k 4k 6k 8k
Directional Microphones & Client Use • Equalizing response increases microphone noise • whole response is boosted • highs are “trimmed” off
Directional Microphones: Effectiveness Measures • Polar plots • theoretical ones are perfectly rounded • derived from a single mic in a sound field • On specs sheets (reality) • mic is on KEMAR or person • plot is “bent” toward ear wearing aid
Directional Microphones: Effectiveness Measures Some Perfectly Rounded Symmetrical Polar Plots: Omnidirectional Cardioid Supercardioid Hypercardioid
Measuring Directional Effectiveness 4000Hz 2000Hz 1000Hz 500Hz • Did you know that with typical directional mics: • the lower in frequency, the less the pick-up from all directions • the ratio from front to back stays the same, but polar plot shrinks