Electricity and Sound Transducers Audio Signals Cables and Shielding

Sound Environments Physical and Virtual - Working Definitions Physical = Sound we hear Physical environment of the audience / performers. World of physics and acoustics Virtual (electronic) = Audio Systems Electrical signals that are representations or facsimiles of sounds Technical Environment of equipment, wires and “techie”

Sound Environments Physical and Virtual - Working Definitions Microphone Equipment System Speaker PerformersAudience/Performed Virtual Environment Audio Physical Environment Sound Transducers - Link Sound and Audio Environments Simple System Block Diagram

Sound Environments Physical and Virtual - Working Definitions Worlds meet at “transducers” Transducers are devices that convert energy from one form to another. In the theatre:  Convert sound to electrical signals.  Convert electrical signals to sound. Microphones Speakers

Sound Environments Physical and Virtual - Working Definitions Every time a transducer is used, some information is lost No transducers are 100% efficient. The sound represented will change Clipping will occur

Audio Signals Microphone level Typically around 2mV The signal created by a microphone and other low power input devices Typically uses XLR connectors or ¼” RTS (ring-tip-sleeve) Line level Standard voltage for signals between pieces of equipment Ranges between.316V and 1.23V The audio signal from CD players, DAT decks, MD players, mixers Typically uses 1/8” or 1/4” phone plug or TS (Tip-Sleeve) RCA (cinch) Speaker level Much higher voltages depending upon the power ratings of the amplifier and load The signal from power amplifiers to loudspeakers Typically uses Speakon connectors Twist lock Bare wires

Audio Signals Impedance (Z) matching When interconnecting equipment it is important to match levels Sending a line level signal into an input which is expecting a microphone level signal will cause distortion High impedance (High Z) Generally line level signals on unbalanced lines Line outs from audio equipment Outputs from electronic instruments Outputs from mixing desks Low impendence (low Z) Generally microphone level signals on balanced lines Outputs from microphones or Direct Injection Boxes

Audio Signals Direct Injection Box Used to convert an unbalanced Hi-Z speaker or instrument level output to a balanced lo-Z mic level output Usually used to enable an electronic instrument to be delivered long distances on lo-Z lines to minimize noise

For next class Read P , Leonard Learning Basic Soldering handout