Lecture 4-Microphones Flashcards
What is a microphone?
A Transducer, it converts energy from one form to another, sound pressure waves are represented by electrical signals.
We need to know the frequency range of the source we are recording.
Sound sources have different ranges in which they operate.
What is a microphones frequency response?
The range of frequencies that a microphone can reproduce.
When is a sound considered ‘coloured’?
If frequencies are reduced at amplitudes different from that of the original sound. 20Hz warmer, 20kHz colder.
What are the two types of microphones?
Dynamic and condenser microphones.
What are the features of a dynamic microphone?
Can handle high SPL, which makes them excellent for instruments.
Low transient response, that is, the measurement of time it takes for the diaphragm to respond to air movement. The faster the response the more accurately the sound is reproduced.
To capture speech, the mic needs to be very close to the mouth.
Good rejection of background noise, which makes them excellent for journalism.
Their high amount of feedback rejection makes them suitable for stage productions and live events with PA.
What are the features of a condenser mic?
Not as rugged as dynamic mics.
Better transient response that makes recordings sound clearer.
They can capture higher frequencies.
They require phantom power, indicated as PH, 48V, 48, P48 etc.
Certain models of mics can receive phantom power from an internal battery.
The majority of the boom mics used in film and TV are condenser mics and will require phantom power.
How can we describe a mics directionality?
Polar pattern or directivity response. This is a measure of how sensitive the microphone is in different directions.
What is an omnidirectional mic?
A microphone equally sensitive in all directions.
What is a figure of 8 mic?
Mic that rejects sound from the sides.
What is a cardioid mic?
A microphone that rejects sound from the rear.
What is a hypercardioid mic?
A mic with a tighter frontal lobe than cardioid.
Define interference tube microphones:
They are essentially a condenser mic with a long tube attached to it.
Sound on-axis propagates down the tube inattenuated.
Sound coming from off-axis will encounter the slits and bounce around inside the tube until they cancel each other out (at different frequencies)
The longer the interference tube, the better the off-axis rejection.
