Microphone theory

Question 1

What are the 3 most important characteristics of microphones for live sound?

Answer 1

operating principle, frequency response and directionality

Question 2

What are the secondary charateristics most important of microphones in live sound?

Answer 2

Their electrical output and actual physical design

Question 3

What is meant by a microphones operating principle?

Answer 3

The type of transducer inside the microphone, that is, how the microphone picks up sound and converts it into an electrical signal.

Question 4

What is a transducer?

Answer 4

a device that changes energy from one form into another, in this case, acoustic energy into electrical energy.

Question 5

What are the two most common types of transducer?

Answer 5

Dynamic and Condenser

Question 6

What components make up a dynamic microphone

Answer 6

diapragm, voicecoil and magnet which forms a miniature sound-driven electrical generator.

Question 7

Describe how a dynamic microphone works

Answer 7

Sound waves strike a thin plastic membrane (diaphragm) which vibrates in response.
A small coil of wire (voice coil) is attached to the rear of the diaphragm and vibrates with it.
The voice coil itself is surrounded by a magnetic field created by a small permanent magnet.
It is the motion of the voice coil in this magnetic field which generates the electrical signal corresponding to the sound picked up by a dynamic microphone.

Question 8

Which type of microphone requires phantom power?

Answer 8

Condenser micriophones

Question 9

What is another name for a condenser microphone

Answer 9

Capacitor microphone

Question 10

What is another name for a dynamic microphone?

Answer 10

Moving coil microphone

Question 11

What is transient response?

Answer 11

Transient response refers to the ability of a microphone to respond to a rapidly changing soundwave.

Question 12

What is the major factor in a microphones transient response?

Answer 12

Diaphragm weight. For instance, the diaphragm and voicecoil assembly of a dynamic microphone may weigh up to 1000 times more than the diaphragm of a condenser microphone.

Question 13

What is a polar plot/polar pattern graph used for?

Answer 13

polar plots shows the variation in sensitivity as you move 360 degrees around the microphone. aka the pick up pattern

Question 14

Describe the polar response pattern of a cardio microphone.

Answer 14

Cardioid (kar-dee-oid) has the highest sensitivity to sound coming in from directly in front of the microphone capsule (0º), practically no sensitivity to sound coming directly from behind (180º), and a reduced sensitivity to sound coming in from the sides (90º/270º)

Question 15

Describe the polar response pattern of a omni-directional microphone.

Answer 15

An omnidirectional polar pattern picks up sound in a 360-degree radius – it is equally sensitive to sound at all angles. Imagine its pattern as a perfect sphere in three directions.

Question 16

Describe the polar response pattern of a figure of eight microphone.

Answer 16

Figure-8. The figure-8 pattern has the same sensitivity at 0° and 180°; it is the least sensitive at 90° and 270°. It is often used for various stereo recording techniques

Question 17

What is the proximety effect?

Answer 17

The proximity effect is an increase in bass or low frequency response when a sound source is close to a directional or cardioid microphone

Question 18

What do we mean by ‘undesired’ sound – example?

Answer 18

“Undesired”sound may mean the direct or ambient sound from othernearby instruments or just stage and background noise.

Question 19

What do we mean by ‘suitable’ – example?

Answer 19

“Suitable”sound from the desired instrument may mean either thenatural sound of the instrument or some particular soundquality which is appropriate for the application.

Question 20

What do we mean by ‘sufficient gain’?

Answer 20

Sufficient” gain-before-feedback means that the desired instrument is reinforced at the required level without ringing or feedback in the sound system.

Question 21

What is meant when you talk about microphone techniques?

Answer 21

The selection and placement of microphones

Question 22

What are the 4 main objectives of microphone techniques?

Answer 22

to maximize pick-up of “suitable” sound from the desired instrument,
to minimize pick-up of “undesired” sound from instruments or other sound sources.
to provide sufficient gain-before-feedback.
Using Directional Patterns to Reject Unwanted Sources

Question 23

What is another name for speakers?

Answer 23

Output transducers

Question 24

What is High Frequency Beaming

Answer 24

Direct radiators exhibit a feature whereby the high frequencies emitted by the driver tend to be strong on axis of the driver, but fall off rapidly once we move off axis. This is called high frequency beaming.

Question 25

What is a band pass filter?

Answer 25

A band-pass filter “passes” a band of frequencies (a defined range above a low cutoff and below a high cutoff) while progressively attenuating frequencies below the low cutoff and above the high cutoff.

Question 26

What is a high-pass filter?

Answer 26

A high-pass filter is the opposite of a low-pass filter, in that it allows frequencies higher than the cutoff frequency to pass. Similar terminology applies. High-pass filters are also called low cut filters. High-pass filters drive the high frequency drivers in the speaker system.