A microphone is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. It is the first step in the signal chain, after the sound source itself, for recording sound or music.
Most microphones today use electromagnetic induction (dynamic microphone), capacitance change (condenser microphone), piezoelectric generation, or light modulation to produce an electrical voltage signal from mechanical vibration.
Where to find more
From Greek "micros μικρός " (small) and "phonos Φόνος" (meaning murder, also used to indicate sound).
History
- non-electric precursor, the Tin can telephone, and its schematics
- attempts to replace the mechanical string by electric lines can be seen in Bell's drawing on Early history of the microphone
- more text and less photos here: The history of microphones
- nice compilation on Wikipedia (e.g. components, varieties, polar patterns (!), windscreens)
- famous US-microphones in Twelve microphones that made history
Comb filter effect
Sound in air is propagated by longitudinal waves. So sound is subjected to wave effects, which are what you hear when recording microphone signals.
- interference on Wikipedia coming from different lengths of paths from A to B
- The basics about comb filtering (and how to avoid it) shows the paths in a recording situation, its effect in spectra and gives audio examples
- Comb filtering: What is it and why does it matter presents the same subject from a slightly different perspective
- comb filter effects have their place in signal processing/electronics as you can see in this Wikipedia article
- for wave effects it's best to turn metres or feet (human dimensions) into multiple of wave lengths; find a nice calculator here, which takes into account different media, temperatures, units
- relevance from said calculator and above articles: sound in air, 20degC, 1150 Hz (voice) are approx. 1 wave per ft
