Hearing and Sound Introduction • Hearing and Sound • Sound Waves • Wavelength • Frequency • Octaves and Bands • Harmonics
Hearing and Sound The mechanics of human hearing • Outer ear • Ear canal • Ear drum • Middle ear • Cochlea
Wavelength Wavelength: Distance between two points that occur at the sample place.
Frequency Frequency: Number of cycles completed in one second.
Octaves and Bands Octave: Interval between a frequency and the doubling of that frequency
Harmonics Harmonics: Whole number multiple of a fundamental frequency. Complex waveforms: Comprised of a fundamental frequency plus many harmonics.
Human Perception of Sound Introduction • Human Perception of Sound Introduction • Logarithms • Decibels • Decibels Equations • Using the Decibel • Inverse Square Law and Sound
Logarithms Number of times the number 10 must be multiplied by itself to get a desired value Logarithmic scales make ratios easier to express We perceive our world in a logarithmic way
Decibels • Describes ratios with a wide range of values • Quantifies relationship between two numbers • In AV used for power, distance, voltage, and sound pressure
Decibels Equations Power: dB = 10 * log (P1 / P2) Voltage: dB = 20 * log (V1 / V2) Distance: dB = 20 * log (D1 / D2)
Inverse Square Law and Sound • Energy inversely proportional to square of distance from source • 6 dB reduction is a doubling of distance • 6 dB gain is a halving of distance
Acoustics • Acoustics • Sound Energy • Reflected Sound Energy • Reverberation • Absorption • Transmission • Ambient Noise
Sound Energy Reflection: Energy sent back into a room Absorption: Energy absorbed into a medium Transmission: Energy passes through a medium
Reflected Sound Energy Echo: Delays due to time and distance
Reverberation Numerous persistent reflections Live environment High level energy Multiple reflections
Absorption Porous Materials • Carpets • Acoustic tiles • Curtains • Clothing
Transmission Energy passing through surfaces • Walls • Floors
Ambient Noise Any sound other than the desired signal • Air conditioning • Equipment fans • Machines • Sound through windows
Microphone Types Introduction • Audio Signal Pathway • Dynamic Microphone • Condenser Microphone • Phantom Power • Electret Microphones • Microphone Physical Design and Placement
Audio Signal Pathway Energy: Acoustic to electrical to acoustic
Dynamic Microphone • Response of diaphragm to pressure • Movement induces voltage • No power source
Condenser Microphone • Capacitor: Diaphragm and fixed back plate • Power Source • Electret Microphone • Size • Battery Option
Phantom Power • Remote Power Source • Mixer • Outboard Supply • 12 - 48 volts DC
Electret Microphones • Type of condenser mic • Named after prepolarized material applied to the diaphram or backplate • Requires less voltage than a typical condenser • Can be very small
Microphone Physical Design and Placement Surface Mount Shotgun Handheld Gooseneck Lavalier
Microphone Specifications Introduction • Microphone Polar Patterns • Microphone Sensitivity • Microphone Frequency Response • Microphone Impedance
Microphone Polar Patterns Omnidirectional Cardioid Supercardioid Bi-directional • Hypercardioid: Variant of cardioid. • Directional, rejects sound from sides.
Microphone Sensitivity • Output level referenced to input level • Condensers vs. dynamics
Microphone Frequency Response Microphone Frequency Response: The range of frequencies a microphone can transduce.
Microphone Impedance • Low impedance ( <200 ohms) • High impedance ( >25k ohms) 200 ohm mic level output 2000 ohm mic level input
Microphone Signal Transport Introduction • Wireless Microphones • Microphone Cables and Connectors
Wireless Microphones • Radio frequency transmission • Hands free
Microphone Cables and Connectors • Shielded twisted pair cable • XLR male and XLR female
Audio Signal Levels Introduction • Audio Signal Levels • Signal Level Compatibility • Signal Level Adjustments
Audio Signal Levels Microphone preamplifier boosts a mic level signal.
Signal Level Compatibility • Inputs and signal level • Microphone input, mic level signal • Line level input, line level signal • Powered loudspeaker • Operating manual
Audio Components Introduction • Audio Mixers • Audio Processors: Compressions, Limiters, and Expanders • Audio Processors: Gates and Filters • Equalizers • Delays • Power Amplifiers
Audio Mixers • Multiple inputs to one or more outputs • Identifying mixer configurations
Audio Processors: Compressions, Limiters, and Expanders • Processors: Control dynamic range with defined thresholds • Compressor: keeps loud signals from being too loud • Limiter: creates a ceiling to prevent signal spikes from damaging equipment • Expander: Reduced unwanted background noise
Audio Processors: Impact on a Signal Audio Compressor:Impact on Signal Audio Limiter:Impact on Signal