COMD 5070 Final Exam Study Guide Questions & Answers (RATED A+)
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Course
COMD 5070
Institution
COMD 5070
What is Science? - ANSWER-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 co...
COMD 5070 Final Exam Study
Guide Questions & Answers
(RATED A+)
What is Science? - ANSWER-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.) - ANSWER-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.?) - ANSWER--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? - ANSWER-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?) - ANSWER-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) - ANSWER--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?) - ANSWER--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=
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. - ANSWER-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 - ANSWER-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
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.
Nyquist Frequency - ANSWER-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 - ANSWER--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)
Spectrum-Line - ANSWER-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.
X=Frequency y=amplitude
3D Spectogram features (3 dimensions) - ANSWER-1. x- TIME
2. Y- FREQUENCY
3. INTENSITY - darkness indicates more energy lighter shows less energy
Hybrid showing both time and frequencies.. evolving over time.
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