489Chapter 16
Microphones
by Glen Ballou, Joe Ciaudelli, and Volker Schmitt
16.1 Introduction............................................................................ 493
16.2 Pickup Patterns......................................................................... 493
16.2.1 Omnidirectional Microphones.......................................................... 494
16.2.2 Bidirectional Microphones............................................................ 495
16.2.3 Unidirectional Microphones............................................................ 495
16.2.3.1 Proximity Effects................................................................. 497
16.3 Types of Transducers.................................................................... 502
16.3.1 Carbon Microphones.................................................................. 502
16.3.2 Crystal and Ceramic Microphones...................................................... 503
16.3.3 Dynamic Microphones................................................................ 503
16.3.3.1 Unidirectional Microphones........................................................ 506
16.3.4 Capacitor Microphones................................................................ 507
16.3.4.1 Voltage Divider Capacitor Microphone.............................................. 508
16.3.4.2 Phantom Power for Capacitor Microphones............................................ 510
16.3.4.3 Capacitor Radio-Frequency, Frequency- Modulated Microphones.......................... 511
16.3.5 Electret Microphones.................................................................. 515
16.4 Microphone Sensitivity7................................................................................................. 516
16.4.1 Open-Circuit Voltage Sensitivity....................................................... 516
16.4.2 Maximum Power Output Sensitivity7.............................................................................. 516
16.4.3 Electronic Industries Association (EIA) Output Sensitivity.................................... 517
16.4.4 Various Microphone Sensitivities........................................................ 518
16.4.5 Microphone Thermal Noise............................................................. 518
16.5 Microphone Practices.................................................................... 519
16.5.1 Placement.......................................................................... 519
16.5.1.1 Microphone-to-Source Distance..................................................... 519
16.5.1.2 Distance from Large Surfaces....................................................... 519
16.5.1.3 Behind Objects.................................................................. 520
16.5.1.4 Above the Source................................................................. 520
16.5.1.5 Direct versus Reverberant Field..................................................... 520
16.5.2 Grounding.......................................................................... 520
16.5.3 Polarity............................................................................ 521
16.5.4 Balanced or Unbalanced............................................................... 521
16.5.5 Impedance......................................................................... 522
16.6 Miscellaneous Microphones............................................................... 522
16.6.1 Pressure Zone Microphones (PZM)..................................................... 522
16.6.1.1 Phase Coherent Cardioid (PCC)..................................................... 524