Microphones

Question 1

What are microphones?

Answer 1

A microphone is a devise used for converting sound waves into electrical energy.

The main purpose is to record or amplify a sound source.

Question 2

Name 4 the different types of microphones

Answer 2

1. Dynamic
2. Condenser (Capacitor)
3. Ribbon
4. Boundary

Question 3

How does a Dynamic microphone work?

Answer 3

There is a diaphragm and coil in the microphone. The diaphragm moves backwards and forwards through the coil. The force of the magnetic field induced an electric current in the wire.

Question 4

What are the pros and cons of Dynamic microphones?

Answer 4

Pros

• robust
• don’t require phantom power
• cheaper
• good for high volume levels

Cons

• will only work effectively up to 16kHz
• small sound output so lots of amplification needed
• poor transient response
• have to be close to the mic

Question 5

How does a Condenser microphone work?

Answer 5

A condenser microphone has two plates that vibrate to create a signal. The diaphragm moves backwards and forwards which generates a current. You need a voltage goof through the condenser for this to work. You can either have a battery inside the mic or use an external 48volts of phantom power.

Question 6

What are the pros and cons of a Condenser microphone?

Answer 6

Pros
- very light in weight
- good at picking up high frequencies
- can make virtually any sound polar pattern
- high output levels so less amplification needed
Sensitive with good transient response

Cons

• very fragile
• can be expensive
• needs phantom power to work
• loses sensitivity is used in a humid environment

Question 7

How does a Boundary microphone work?

Answer 7

These work the same as Capacitor microphones, but contain a pressure capsule which detects the small changes in air pressure as sound travels around the room.

Question 8

What is a Boundary microphone?

Answer 8

Boundary microphones are designed to be used at a boundary of a room (e.g. wall or floor). These microphones consist of a flat plate which picks up sound waves as they reflect and bound off the boundary plate.

Question 9

What are the Pros and Cons of Boundary microphones?

Answer 9

Pros

• direct and reflected sounds arrive at the microphone at the same time which makes it more responsive
• can pick up higher frequencies than the human ear can hear
• high out levels so less amplification needed
• detailed, clear sound and good at high-frequency pick-up
• sensitive with good transient response l

Cons

• can be expensive
• loses sensitivity in a humid environment
• not robust, can be easily damaged
• needs 48v phantom power to work

Question 10

How does a ribbon microphone work?

Answer 10

Ribbon microphones consist of a thin metallic strip of foil, suspended in front of a magnetic plate. Sound waves make the foil to vibrate, producing fluctuations in the electrical current, creating the audio signal.

Question 11

What are the Pros and Cons of Ribbon microphones?

Answer 11

Pros

• produces warm and rich representation of the original sound
• it picks up a wide range of frequencies (beyond the human hearing)
• high output levels so less amplification needed
• extremely sensitive with good transient response

Cons

• it’s very sensitive therefore could be easily damaged
• not portable
• can be very expensive
• needs 48v phantom power

Question 12

What are the four possible polar patterns?

Answer 12

1. Cardioid
2. Figure of 8
3. Hyper-cardioid
4. Omni Directional

Question 13

Cardioid

Answer 13

Picks up the sound from the front axis of the microphone

Question 14

Hyper Cardioid

Answer 14

It is even more frontward’s directional pattern with minor rear spill

Question 15

Figure of 8

Answer 15

It picks up sound equally from both the front and the rear of the microphone

Question 16

Omni Directional

Answer 16

Picks up sound equally from all sides of the microphone

Question 17

Name 4 considerations when setting up the microphones

Answer 17

1. The proximity effect
2. Room ambience/reflections
3. Noise reduction and room treatment
4. Spill from other instruments

Question 18

Close Microphone Technique

Answer 18

This is when the microphone is very close to the source and it captures the full colour and sound.

Question 19

AB Stereo Pair / Spaced Pair

Answer 19

An exact pair of microphones spaced at a minimum of 1m away from the sound source.

Question 20

Coincident Pair or XY Pair

Answer 20

Two microphones positioned with a 90 degree angle on top of each other. The centre of the two microphones should be aligned with the sound source.

Question 21

Blumlein Stereo Pair

Answer 21

This is essentially the same as the XY Pair but with two figure of 8 polar patterns, instead of two cardioids.

Question 22

Mid-side Stereo Pair

Answer 22

Two microphones, the front is a cardioid and the side microphone is Figure of 8. These microphones are placed on top of each other. The Figure of 8 is duplicated and panned R/L, one of which should be reverse phased, and the Cardioid is panned in the centre.