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COMD 5070 Final Exam Study Guide Exam/64 Questions & answers
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COMD 5070 Final Exam Study GuideExam/64 Questions & answers
What is Science? - -1. Empirical: Based on data
2. Deterministic: Obeys physical laws of cause and effect (not random)
3. Predictive: if you do this...then that will happen; it can influence another
one
4. Parsimonious: use simplest explanation possible rather than make
unnecessarily complicated - boil it down to its essence, without dumbing
down.
-Semitones (how many semitones in one octave, two octaves, etc.) - -
Octave: changes mathematical relationship bw frequencies; doubling
(up)/halving (down) of frequency 400= 800 (up) & 200 (down)
-12 semitone= 1 octave
200-400Hz=1 octave = 12 semitones
200-800Hz=2 octaves = 24 semitones
-Sampling Rate (How does it relate to playback quality, file size, frequencies
saved in Recording, nyquist, etc.?) - --Sampling Rate (snapshots): (specified
in Hz) frequency of numbers stored/written to act as sampled analog signal:
discrete snapshots in rapid succession. Linked with quality level. Numbers
represent amplitude values; more samples, better can represent original
signal. Rapidly changing signal needs more samples/dos to reflect all
changes in original. Too low sampling rate & changes missed. Think movie
shot @ 30fps looks continuous. Any lower tho would look jerky.
-Higher Sampling Rate selection: gives better fidelity; BUT= files & storage
disk space uses more memory processing time, & computational power.
Nyquist Frequency=Half of sample rate. Highest freQ can record & play back
accurately. Must sample @2x rate of the highest FreQ. Ex: CD sample
rate=44,100 amps or snapshots/sec & stores signal up to 22,050Hz
(corresponds to upper limit of most ppls hearing). To record up to 100Hz,
SR=200Hz 1/2 Sample Rate=Nyquist FreQ (100HZ=original amount).
-Filter types (What do high or low pass or band pass or band reject filter do?
- -1. High Pass Filter - Allows High frequencies thru but removes or
attinuates or holds lower Frequencies
2. Low Pass Filter - Allows lower frequencies thru but removes or attinuates
or holds higher Frequencies
3. Band Pass Filter - Allows a band of frequencies thru but removes or
attinuates or holds higher and lower Frequencies
4. Band Reject Filter - Allows a both higher and lower frequencies thru but
removes or attinuates or holds a band of Frequencies
, -Fourier Transforms/Analysis (What is result of Fourier transform of sound?
What does it reveal about complex sound?) - -Came up with way of
analyzing complex signals and decomposing or splitting them into a series of
individual components.
1.All periodic sounds are made of a combination of since waves.
2.You can break them up
-amplitudes vary (how big they are)
-phase angles vary (where they are in cycle)
-frequencies vary (many dif freq)
Fourier taught us that Even complex sounds can be broken down into their
ind. sinoudal components.
FOURIER TRANSFORM - We take a time domain waveform (like microphone
signal) and we analyze it and create a spectrum from the time domain
waveform
- Analyze a cake to learn its ingredients.
Time domain x-time y-amplitude THEN fourier transform =Frequency domain
(spectrum:slice in time) x-frequency y-amplitude
-Time Domain Data (TDD) - --a waveform represents sound directly
-(air pressure) changes over time.
x- TIME y- AMPLITUDE
-Types of Spectra: Line, FFT, LPC, (they reveal different features of speech;
What is each one best suited for?) - --Waveform: Time domain view of
sound.
-Spectrum: FreQ domain view of sound. Indiv ingredient @ single point in
time. (X=FreQ; Y=Intensity) Spectra: Plural form of spectrum
-Line Spectrum: (Type of FDD) shows FreQ components of periodic sound.
Singel vertical line=Sine wave. Ea vercl line is single freQ=
-Nyquist Frequency - -The Nyquist frequency comes into play during the
recording or digitization. If you select a sample rate of, say, 16,000 Hz, then
the Nyquist is half of that, or 8,000 Hz. This means in practical terms that
frequencies up to 8,000 Hz in your incoming analog signal (from the
microphone) will be correctly recorded and can be played back. But
frequencies above 8,000 Hz will not be saved. Most modern recorders and
computers will automatically low-pass filter your incoming signal at the
Nyquist frequency to prevent aliasing, which would contaminate your
recording with incorrectly saved frequencies that are above the Nyquist. So
it's during recording that we are interested in the Nyquist.
-Fourier Transform = Frequency domain display - --A line SPECTRUM shows
the frequency components of a periodic sound.
, -Frequency domain description of the signal
-has harmonics that are multiples of the fundamental
-has nothing bw the lines (the lines represent the harmonic frequencies)
x-FREQUENCY y - AMPLITUDE
Has split up each individual sound from the total so u can hear each
individually.
Benefit - is to show us what those ind. components are and the relative
proportions of each height of each bar says the strength of each.
This is like our human speech and it is 'NEARLY PERIODIC'
The upper harmonics get progressively weaker as you go up in frequency.
-What does each Time vs frequency domain displays shows us about sound.
- -1. Time domain - shows us the time view
x- time y-Amplitude
2.Frequency domain - shows us the frequency view. -sine wave: single line
on a spectrum
-complex periodic signals: multiple lines
x-frequency y-Amplitude
3.What would noise look like in a spectrum ?
-all frequencies
-equal amplitude
-random phase
-Spectrum -(FFT) Fast Fourier Transform - -1. Clearly shows us range of
HARMONIC energy
2. each peak is a harmonica
3. BUT will not show us / less clear at showing formants.
4. more revealing of the (source) = problem with voice
-Spectrum - (LPC) Linear predictive coding - -1. Shows SPECTRAL ENVELOPE
2. good at revealing formants
3. doesn't show harmonics
4.more revealing of filter = articulation problems
5. ***will show you what the vocal tract is doing where its resonant
frequencies are relevant to one another.
-Spectrum-Line - -1. A line spectrum is a snapshot in time.
2.a line spectrum shows the FREQUENCY COMPONENTS of a periodic sound.
3. A pure tone has a single vertical line on a spectrum.
4.Not sure about this..Separates them individually with heights showing
strength of each. Represent the harmonic frequency.
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