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Sound/Frequencies
N/A
41
Engineering
Undergraduate 1
09/23/2014

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Term
what is sound?
Definition
waves of varying pressure in a given medium, alternating compression and rarefaction
Term
what is (a) frequency?
Definition
rate at which a periodic wave repeats
Term
what is frequency measured in?
Definition
Hertz, or "cycles per second"
Term
lower sounds = _________
higher sounds = _________
Definition
fewer cycles; more cycles
Term
range of human hearing
Definition
20 Hz - 20,000 Hz
Term
propagation of sound
Definition
movement of sound through air or other medium
Term
what is the opposite of a sine wave?
Definition
white noise from a random signal generator (constant spectral density)
Term
what is an octave?
Definition
double frequency of original pitch
Term
what is pink noise?
Definition
similar to white noise, weighted towards the low end of the spectrum as opposed to no weight in white noise. warmer, quieter, lower
Term
what are overtones?
Definition
not naturally vibrating material produces a simple sine wave
Term
what is the harmonic series?
Definition
any vibrating string also vibrates at the octave above it, and the octave above that, ect ect.
Term
vowels are _______
consonants are _______
Definition
harmonic; transients/sound structures
Term
what is timbre?
Definition
harmonic content that defines the characteristic of a sound
Term
what is amplitude?
Definition
represents air compression and rarefaction
Term
compression goes ______ and rarefaction goes ______
Definition
up; down
Term
what unit is used to measure amplitude?
Definition
decibel
Term
what is a decibel?
Definition
logarithmic unit used to express the ratio between two values of physical quantity, often power or intensity.
Term
why is the decibel used?
Definition
it’s a versatile scale that possesses the logarithmic structure that makes it easy to render ratios of great difference
Term
what is the decibel used for?
Definition
measure differences in air pressure, and to calculate the degree to which we amplify or attenuate an audio signal
Term
what amount doubles/halves the perceived loudness?
Definition
+/- 10 db
Term
what is the smallest increment humans can perceive?
Definition
+/- 3dB
Term
psychoacoustics are _______
sound pressure level (SPL) is ______
intensity/power are _________
Definition
subjectively perceived; objectively measured; theoretically calculated
Term
what does the equal loudness contour attempt to do?
Definition
represent the variation in perceived loudness across the frequency spectrum
Term
what is are two examples of the equal loudness contour?
Definition
robinson-dadson curves and ISO 226:2003
Term
what is a wavelength?
Definition
the point between successive crests of a periodic wave
Term
what decibel level are humans most sensitive at?
Definition
2-4K
Term
what is a phon?
Definition
unit of loudness level for pure tones
Term
the number of phons of a sound equals what?
Definition
the dB SPL of a sound at a frequency of 1kHz that sounds just as loud
Term
what is the threshold?
Definition
the point at which a sound becomes inaudible
Term
what is a transducer?
Definition
a device that converts variations in a physical quantity, such as pressure or brightness, into an electrical signal, or vice versa
Term
how does polarity play out in audio signals?
Definition
towards the positive is typically the compression, and towards the negative is typically the rarefaction
Term
describe unbalanced cables.
Definition
transmits an audio signal through two lines: the signal ("hot") and the ground. the receiving device interprets the signal by comparing the hot and ground signals, and any noise or interference picked up along the length of the cable is then included as part of the signal. avoided over 20ft, common connections are TS and RCA
Term
describe balanced cables.
Definition
carries the signal via three lines: normal polarity ("hot"), reversed polarity ("cold"), and ground. the receiving device flips the reversed polarity signal which cancels out most noise acquired along the length of the cable. results in a more accurate representation of the source with less noise. common cables are TRS and XLR.
Term
what is a frequency response?
Definition
quantitative measure of the output spectrum of a system or device in response to a stimulus*
Term
what is frequency response plotting relevant for?
Definition
inputs, amplifiers, effects/processors and outputs
Term
an equal loudness contour is like...
Definition
a frequency response plot for human ears
Term
what is flat frequency response?
Definition
accurately reflects the sound/signal received
Term
what is dynamic range?
Definition
describes the difference between the loudest and quietest portions of an audio signal. can refer to a particular recording or the potential of a particular device
Term
what are the two instruments that show metering signal levels?
Definition
the VU and peak meter
Term
describe the VU.
Definition
described RMS voltage (root mean square). slightly delayed, but displays "average loudness." slow response and release times (300 ms)
Term
describe peak meter.
Definition
displays peaks (transients). fast response, release of actual peaks can be delayed (typically a controllable parameter)
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