Chapter 1 Sound Reinforcement Flashcards
Sound is technically called _______.
acoustical energy
Acoustical energy is the pushing and pulling of a _____.
physical / medium (usually air)
A complete wave cycle is 1/2 cycle of ____, followed by 1/2 cycle of ____.
compression / rarefraction
A rate of ___ is called the frequency.
fluctuations
To be called sound, the frequency must be between ____ cycles per second (cps)
20 and 20,000
The unit of frequency is ___.
Hertz (Hz) 20 Hz = 20cps
Sound waves travel through air at ___.
1130 ft/second (at sea level and temp of 59 degree F
___ is independent of frequency.
Speed of sound
Physical measurement of a wave is the ___. Wavelength = ____
wavelength / speed/frequency
An ___ is an electrical version of sound; audio equipment, the ___ or ___ fluctuates at the same rate as the accoustical energy.
audio signal
voltagee
current
The amplitude or strength of an audio signal is called the ____.
signal level
Relationship between a wave and known time reference is called the ____.
phase
___ is expressed in degrees. One complete cycle of a ___ equals 360 degrees.
phase / sine wave
___ is very important in sound systems. Phase must be controlled because it effects how sounds add together.
Phase
When ___ are mixed in a console or in the air, they add algebraically.
audio signals
A sound system is a system of electronic components that’s designed to amplify sound. Name the three most common reasons.
Help people hear better.
Make sound louder for artistic reasons.
Enable people to hear sounds in remote locations.
Sound systems convert ___ energy into ___ energy, modifying the ___ energy and then converting it to ___ energy.
acoustic / electrical / acoustic
In audio electronics, devices that convert energy from one form into another are called ___. Devices that change one or more aspects of an audio signal are called ___.
transducers
signal processors
Input transducers convert ___ energy into ___ energy; then signal processors alter one or more characteristics of the ___. Output transducers convert the ___ energy (amplified for otherwise processed) back into acoustic energy.
acoustic / electrical / audio signal / electrical
Examples of input transducers
Air pressure or velocity microphones, contact pickups, magnet pickups, tape heads, phonograph pickups (cartridges), lazer pickups, optical pickups.
Examples of output transducers
woofer, midrange, tweeter, full range, subwoofer, supertweeter, monitor, and headphones
Name the three devices that make up a basic model of sound system.
Input transducers (microphones), signal processing (mixing console -> power amplifiers) output transducers (loudspeakers)
___ describes the relationship between a device’s input and output with regard signal frequency and amplitude, gives the usable range of signal frequencies for a device.
frequency response
What’s the range and tolerance of 30Hz to 18Hz, +3dB?
Range for 30Hz to 18Hz, tolerance 3dB (maximum expected deviation between output and input over the range).
The ___ is an interval between two tones - ratio frequency of the tones 2:1
octive
Response of dynamic microphones used in sound work falls off rapidly above ___
10kHz
Loudspeakers usually have the ___ variations in frequency response.
greatest
Differences in dividing sound reinforcement and loudspeakers (full/limited).
Full do most frequencies pretty well.
Limited - narrower frequency bands, but do it better than full range. Typically they are used together in some way.
Describe differences in full-range reinforcement, subwoofers and tweeters.
Full-range reinforcement have a frequency response from 100Hz to 15Hz. Subwoofers typically designed below 200Hz and usually perform down to 30Hz. Tweeters above about 8kHz
Speaking voice range is typically ____ and has very little high frequency content, a loss of frequencies above ___ can affect intelligibility.
100Hz - 6Hz 1 kHZ
When a complex waveform has a distinct pitch, that waveform can be created by combining a set of precisely related sine waves called ___.
harmonics
Effects of acoustical factors (indoor and outdoor)
Indoor - reflections from the wall, ceiling and floor surfaces, room resonances.
Outdoor - wind - modulate the sound
Temp - reflects or retracts sound.
Humidity - effects high frequencies
When sound travels through air, ___ frequency signals are absorbed faster than ___ frequency signals.
high / low
