Capture of sound - taken from revision guide

Question 1

Give the three types of Microphone

Answer 1

1) Dynamic 2) Condensor 3) Ribbon

Question 2

Describe how a dynamic mic captures sound (5 steps)

Answer 2

1) A moving coil is attached to a diaphragm 2) This diaphragm moves in response to the changes in air pressure 3) When sound enters, the diaphragm vibrates 4) The coil moves in a magnetic field and a varying electrical current is induced that is proportional to the changes in air pressure 5) This is called electromagnetic induction

Question 3

Describe how capacitor microphones work (3 steps)

Answer 3

1) Sound causes the diaphragm to vibrate 2) When the diaphragm vibrates, the gap between the two plates changes 3) The plates are powered, therefore moving the diaphragm causes a change in capacitance and a current flows

Question 4

Give four points about dynamic microphones

Answer 4

1) Can withstand high SPL 2) Resistant to moisture 3) Good for live use 4) No phantom power needed

Question 5

Give four points about condensor microphones

Answer 5

1) High sensitivity - effective capture of quiet sounds 2) Flat frequency response 3) Phantom power (+48V) required 4) Brigher signal than dynamics

Question 6

Give 4 points about ribbon microphones

Answer 6

1) Sound vibrations disturb a metallic ribbon suspended in a magnetic field 2) ‘Warm’ sound when close-miking with emphasised low-frequencies 3) Fragile and often very expensive 4) Damaged or broken by phantom power

Question 7

Give 5 controls one would find on a pre-amp

Answer 7

1) Phantom power 2) Gain 3) Pad 4) High pass filter (HPF) 5) Polarity inversion

Question 8

What do pre-amps do?

Answer 8

Convert the signal into a workable line level

Question 9

What is phantom power?

Answer 9

It boosts the signal by +48V so that it charges the capacitor of a condenser mic and its internal pre-amp

Question 10

What is a polar pattern?

Answer 10

How a microphone picks up sound from around the capsule

Question 11

Give four polar patterns

Answer 11

1) Omnidirectional 2) Cardioid 3) Hypercardioid 4) Figure-of-8

Question 12

Give three points about an omnidirectional polar pattern

Answer 12

1) Picks up sound from all around the capsule 2) Captures room ambience 3) Provides little isolation so can lead to spill being captured

Question 13

Give three points about a cardioid polar pattern

Answer 13

1) Rejects sound from the behind 2) Used for most close-mic work 3) Minimises the amount of reverb and/or noise that is captured behind the microphone

Question 14

Draw a hypercardoid polar pattern and briefly describe it

Answer 14

It is a midway point for some room ambience and some instrument isolation

Question 15

Give three points about a figure-of-8 polar pattern

Answer 15

1) They are used in M/S (mid-side) arrangements to give a stereo image
2) Strongly rejects sounds from the sides of the capsule
3) Often used for interviews

Question 16

Which polar patterns exhibit the proximity effect

Answer 16

All directional polar patterns (basically all apart from omnidirectional)