4 Flashcards
How is a sound wave formed
Vibration moving compressible medium (air) and radiating alternating waves of compression and rarefaction
Wavelength
Distance between two points that occur at the same place in a cycle
Zero-reference line or reference levels
The center line which represents molecules at rest position
Frequency
The number of wave cycles occurring in the period of a second. Measured in hertz (Hz).
What is the spectrum of human hearing?
20Hz to 20kHz
Harmonics
Additional vibrations to a fundamental frequency
________ are used for quantifying differences in measurements of voltage, power, distance, or sound pressure.
Decibels
A measurement of the amount of data or a signal that can pass through a system during a given time interval
Bandwidth
As technological limitations of signal sampling rates have progressively been overcome, pro audio applications tend to use higher sample rates to capture more subtle waveform variations in the source signal. What are these sample rates?
48kHz, 96kHz, or 192kHz
CD audio is set at 16 bps. To reduce quantization errors, these bps measurements are employed in many professional audio applications.
24 bps or 32 bps
PCM, AIFF, MPEG, HDMI audio, AES3, and WAV are examples of what kind of audio data formats?
Uncompressed
A branch of science that focuses on the qualities and characteristics of sound waves
Acoustics
___ ___ __ ____________ __ ______ tells us that total energy neither increases or decreases in any process
The law of conservation of energy
When sound energy encounters a surface or room boundary, some combination of these three things will happen
Reflection, absorption, transmission
As energy reflects off more surfaces around a room, the listener begins to receive reflected energy from all directions. When the energy level remains high and the reflections become dense in relation to one another, this is called:
Reverberation
What is transduction?
The conversion of energy from one form to another
A microphone with a diaphragm attached to a moveable coil of wire located in a magnetic field.
Dynamic microphone
The very low-level signal from a microphone. Typically only a few millivolts.
Mic level
Also called a capacitor mic, a microphone that transduces sound into electricity using capacitive properties
Condenser mic
A type of microphone using a pre-polarized material which is applied to the mics diaphragm or backplate
Electret mic
Mechanical devices built directly onto silicon chips using the same fabrication processes as microprocessors and memory systems
Microelectromechanical systems, or MEMS
Remote power used to power a range of audio devices
Phantom power
This term is used to describe mic’s directional capabilities
Polar pattern
This characteristic defines electrical output signal level given a reference sound input level
Sensitivity
What is frequency response?
The mic or loudspeaker’s electrical output throughout the audible frequency spectrum.
____________ turns mic level into a more robust line level before the signal is processed
Preamp
Electronic signal amplification
Gain
Attenuation
To reduce amplitude of signal or current
____ _______ refers to the general ability to make adjustments to the signal levels
Gain adjustments
What is unity gain?
The lack of gain and attenuation to a signal. It means the signal is passing through the audio system without any changes to its level.
How sound moved through the air is called ___________
Propagation
Which of the following does 0dB SPL describe?
A. The threshold of human hearing
B. Ambient noise level
C. The threshold of pain
D. Normal listening level
A. The threshold of human hearing
A “just noticeable” change in SPL, either louder or softer, requires a change of how many dB?
+/-3dB
The properties or qualities of a room or building that determine how sound is transmitted and reflected. The study of the properties of sound.
Acoustics
The audio signal ends up in a ______ _______ before being converted into an electrical signal.
Output device
The simultaneous use of multiple wireless microphone systems requires ________ ____________.
Frequency coordination
What is a crossover?
An electronic device that separates the frequency bands of an audio signal so that each driver in a multi driver loudspeaker system is sent only those frequencies that it will transduce accurately.
Audio processor that:
•reduces the level of all signals above an adjustable threshold
•reduces the variation between the highest and lowest signal levels
•can be used to prevent signal distortion
Compressor
Audio processor that:
•limits the level of all signals above an adjustable threshold
•is used to prevent damage to components such as loudspeakers
•are triggered by peaks in audio signal like a dropped microphone
•essentially extreme compression
Limiter
Audio processor that:
•Reduce the level of all signals below an adjustable threshold
•Increases variation between highest and lowest signal levels, resulting in increased dynamic range
•are used for reducing unwanted background noise
Expander
Audio processor that:
•can be thought of as extreme downward expander
•mute the level of all signals below an adjustable threshold
•can be used to automatically turn off unused mics
Gate
