What is A/V? Understanding Signal Flow:

- Introduction to AV systems and typical use scenarios

- Introduction to signal flow in respective systems (Live Audio, Studio-based production)

- Key Personnel in the respective disciplines (Live Audio, Studio-based production)

- Scalability of A/V Systems

- Compatibility of audio equipment

- Different types of Audio Cables/Connections

- WHS Considerations

Learning Activities

- In groups discuss what signal flow is?

- Cable Rolling

- Explain the signal flow of the studio you are currently learning

Content

- Define what a transducer is

- Different types of microphones

- Basic operating principles of microphones:

• Dynamic
• Ribbon
• Condenser

- What is a microphone polar pattern and what are the main ones?

Microphone Theory 1

• Purpose of Microphones

• Microphone designs

• Microphone polar patterns

• Microphone Frequency response

• Proximity effect

Dynamic Microphones

MOVING COIL

Pros:

• No need for external power
• High SPL
• Robust
• Cheap to manufacture
• Withstands high relative humidity

Cons:

• Low output level (1 to 5 mV / Pa)
• Bad High Frequency response (16 to 17k)
• Bad Transient response
• High self noise

RIBBON

Pros:

• No need for external power
• Great High Frequency response(≈18k)
• Very good Transient response

Cons:

• Low output level (1 to 5 mV / Pa)
• Can’t handle high SPL
• Very fragile
• Sensitive to humidity

Condenser Microphones

Pros:

• Good High Frequency response (> 18k)
• Good Transient response
• High output level (15 - 40mV / Pa)
• Low self noise
• Switchable polar patterns

Cons:

• Needs some form of power
• Can’t handle high SPL
• Fragile
• Sensitive to humidity
• High handling noise

Other Microphones

Electret Microphones

They may be cheap but they are used in phones mostly and aren't common at all in studio based environments.

Valve Microphones

use a valve circuit to amplify the current as opposed to a transistor circuit used in later solid state models. It is the ‘soft clipping’ of the high end that produces the ‘warm’ sound.

Crystal Microphones

Largely obsolete. Light rigid diaphragm made from 2 slices of piezo-electric material which generate a small voltage when deformed. Not used for high quality audio reproduction.

Carbon Microphones

Largely obsolete. Pressure on granular carbon balls change the resistance of the carbon. Constant background noise. Used in telephone handsets for most of last century. Not used for high quality audio reproduction.

Polar Patterns

There are 3 main types of polar patterns that a microphone may have.

Omni-Directional:

An omni-directional microphone will pick up sound equally as well in all directions.

Bi-Directional:

A bi-directional microphone (figure-of-eight) will pick up sound equally as well at its front and rear but it will reject sound coming from its side.

Cardioid (Uni-Directional):

A uni-directional microphone will capture sound best from directly in front and it will reject sound from the rear. A cardioid response is achieved by building ports (holes) into the body of the microphone.

There are also two variations of the cardioid polar pattern that a microphone may have. These are called super-cardioid and hyper-cardioid patterns.

Frequency Response:

The frequency response of a microphone refers to its sensitivity with regard to frequency.

A frequency response graph will give us information on how a microphone will “colour” a sound.

It shows relative output level based on the given input level.

Proximity Effect:

• Increase in the low frequency response of a microphone when it is placed up close to a sound source

• This bass boost (particularly noticeable with vocals) will proportionately increase as the distance from the source to the microphone decreases.

•The proximity effect does NOT occur with omnidirectional microphones.