SynAudCon: Core Principles of Audio

• Time, Frequency and Wavelength

• Signal Flow

• Component Interfaces

• System Gain Structure

• Grounding and Shielding

• Loudspeaker Fundamentals

• Equalization

• Mixer Fundamentals

• Digital Mixer Overview

• Microphone Fundamentals

• Controlling Feedback

• Signal Processing

Day 1: Overview of the Audio System Signal Chain

Electronics for Audio

• Sources Loads & Interfaces
• The Voltage Divider in audio circuits

Audio Interfaces

• Professional (Balanced) vs Consumer (Unbalanced) interfaces
• Connectors for sound systems

Audio Source Mixing

• The level / tone hierarchy
• Setting channel gains appropriately
• Summing room

Summary – Interfacing Audio Devices through the Signal Chain

• Review of interface requirements – voltage, impedance and topology
• Gain structure sequencing

Digital Mixer Overview

• Comparison with analogue mixers
• Analogue signals vs digital signals
• Digital sampling theory

System Grounding

• What is grounding? (and what it isn’t)
• Safety protection grounding vs signal ground (aka ‘common’, ‘earth’)
• Ground loop hum – how it occurs and tips for eliminating it (safely!)

Common Interfacing Problems

• Employing interface conversion boxes (Dis and ITs etc)
• Example interface issues and resolutions

Portable System Distribution and Grounding

• An example system to put all the theory into practice!

Connecting Loudspeakers

• Calculating wire line loss, and selecting appropriate wire
• Amplifier damping factor
• Parallel vs Series connection

Power Ratings – Amplifiers and Loudspeakers

• Understanding power ratings vs efficiency
• Matching power amplifiers to loudspeaker ratings
• Understanding loudspeaker sensitivity vs power rating

Day 2: The Decibel

• Why do we use decibels?
• Understanding the form of the decibel
• Subjective relationships with the decibel
• Decibel scales – what does 0dB mean?
• Describing acoustic and electrical quantities

Component Gain Structure

• What is good gain structure?
• Dynamic range vs signal-to-noise ratio
• Typical operating levels for consumer vs professional equipment

Audio Meters

• Introduction to the variety of audio meters – VU, PPM, Peak
• Audio meter ballistics
• Audio meter scales
• Metering through the signal chain

Dynamic Range Control

• Limiting vs Compression vs Auto-Gain-Control
• Application of dynamics control
• Typical settings for dynamics control applications

Frequency

• The audible frequency spectrum – 20Hz to 20kHz
• Audio bands; decades, octaves and fractional octaves
• Wavelengths of acoustic waves

Sound Pressure Level

• Human perception of loudness vs level and frequency – complex!
• Equal loudness contours and weighting scales: dBA, C
• Common real-world sound pressure levels

Time Frequency & Wavelength

• The difference between electrical (“audio”) waves and acoustic waves
• Relationships between time, frequency and wavelength for audio and acoustic waves
• Spherical spreading of acoustic waves and the inverse square law
• Acoustic wave interference

Anatomy of A Loudspeaker System

• Why do we need multiple transducers in a loudspeaker system?
• Multi-way loudspeakers and their transducers
• Crossover networks – passive and active

Loudspeaker Basics

• Goals for all loudspeaker systems
• Define loudspeaker coverage angle – polar response
• Guidelines for loudspeaker aiming and placement

Coverage Considerations

• Consider the relative merits of different approaches to audience coverage
• Define the requirements for the venue – e.g. Evenness? Acoustic imaging? Etc
• Decide on the solution that meets the requirements best

Optimum Loudspeaker Placements

• For speech / mono music
• For large mono systems requiring in-fill loudspeakers
• For stereo music

Line Arrays / Sound Columns

• The theories behind line arrays / column speakers
• Controlled coverage in vertical direction, but not horizontal
• Applications for arrays / columns

Guidelines for Loudspeaker Equalisation

• Measurement and signal processing equipment
• Where to place a microphone for measurement
• Which loudspeakers should be active when measuring?
• What to EQ and what not to EQ…

Microphone Majors

• Dynamic vs condenser microphones
• Phantom power
• Mic variables:
  • Sensitivity
  • Polar pattern
  • Distance
  • Interaction
  • Polarity

Feedback!

• Potential Acoustic Gain vs Needed Acoustic Gain (PAG NAG)
• How to increase feedback stability margin
• Feedback control methods

Signal Processing – Summary

A summary of the correct application of signal processing throughout the signal chain

System Setup Overview for Operators

A review and recap of the course material, in the context of setting up a system from start to finish

Click HERE to download this agenda as a PDF