3_microphones

3_microphones - M i c ro p h o n e s Juan P Bello Early...

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Microphones Juan P Bello
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Early recording • Early recording and reproduction was entirely acoustic • Sound was captured by a horn terminated on a diaphragm that vibrated in sympathy with the sound • The diaphragm was attached to a stylus which cut grooves on foil or wax • Performers had to clutter around the horn. • Little control of individual levels
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Sound in electrical form • Sound in electrical form can be amplified, mixed and recorded. • We can convert the acoustical waveform into an electrical waveform of the same shape • Amplitude becomes voltage (V), and air particle motion becomes electrical current (I) - electrons playing the role of air particles. • The current’s direction of flow changes with cycles of compression/rarefaction creating an alternating current (AC) • The flow of electrons in a conductor is impeded by a certain amount of resistance (R) • The relationship between V, I and R is regulated by Ohm’s law: V = I × R. Their relationship with Power (W) is: W = I 2 × R = V 2 /R • In AC systems resistance is replaced by impedance (which also includes reactance). Impedance is frequency dependent
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Electro-magnetic induction Electromagnetic transducers convert mechanical motion (as produced by, e.g., an acoustic wave) into an electrical signal An electrical current is induced (and voltage is produced) if: (i) a static conductor is situated in a changing magnetic field, or (ii) a conductor moves in a static magnetic field This phenomenon is characterized by Faraday’s law of electromagnetic induction ( http: //msdaif . googlepages . com/demo_faraday ) The direction of motion (perpendicular to the lines of flux) controls the direction of current flow in the conductor (e.g. a wire). Back and forth movements result in an alternating current (AC) related in frequency and amplitude to the wire’s motion Magnet Magnet N S Electro-magnetic field wire Motion of wire
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• Microphones are transducers that convert acoustical energy into electrical energy. • The three main types of microphones (according to their principles
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3_microphones - M i c ro p h o n e s Juan P Bello Early...

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