COMD 5070 Exam 3 UPDATED ACTUAL
Exam Questions and CORRECT Answers
4 features of the scientific method: - CORRECT ANSWER - empirical, deterministic,
predictive, parsimonious
Octave - CORRECT ANSWER - a doubling or halving of a frequency
How many semitones in an octave? - CORRECT ANSWER - 12. each semitone is a non-
linear step in terms of # of Hz from one semitone to the next. However, they all sound equal to
us.
Sampling rate - CORRECT ANSWER - The number of snapshots of the sound in time. (
in Hz) 10 samples is a 10 Hz recording. Generally, the higher the sampling rate, the higher the
fidelity of the recording. Graphic representation of the join the dots graph, the more dots, the
better the image, the fewer, the cruder. A higher sampling rate will take up more space and
require higher processing power.
Nyquist frequency - CORRECT ANSWER - half the sample rate. You determine the
highest frequency you want to include in your recording and double it, this will ensure that the
playback will go at least as high as the original signal. Nyquist determines the highest frequency
you can reproduce in playback. CD sampling rate is 44,100 and it stores signals up to 22,050 Hz.
Aliasing - CORRECT ANSWER - When sampling too slowly, you will inaccurately
record the original signal. High, original frequencies will be improperly recorded as lower
frequencies. Think of the sine wave, where only certain dots were captured, so the original
waveform is "smoothed out" or aliased.
How to prevent aliasing - CORRECT ANSWER - This can be prevented with a low pass
filter at the nyquist frequency, to keep out the high frequencies that might be misrepresented.
High pass filter - CORRECT ANSWER - allows high frequencies and attenuates low
frequencies
, Low pass filter - CORRECT ANSWER - allows low frequencies and attenuates high
frequencies
Band Pass filter - CORRECT ANSWER - Removes high and low frequencies but lets
through the frequencies in the middle
Band reject filter - CORRECT ANSWER - Allows all frequencies except for a specific
band in the middle.
Fourier transform - CORRECT ANSWER - a way to analyze complex sounds by
separating them into their components
How to do a Fourier transform - CORRECT ANSWER - You take a time domain wave
form ( microphone signal - time on x and amplitude on Y) you apply the fourier transform to it
and it gives you a frequency domain wave form ( line spectrum) which represents a slice in time
that has frequency on x and amplitude on y. It's like parsing light through a spectrum which
shows all of the colors. So you can now hear all of the individual sounds that make up the
harmonic series - this is the spectrum / frequency/domain display. Similar to a list of ingredients
of a cake.
time-domain display - CORRECT ANSWER - has time on the X axis and Amplitude on
the Y axis and shows a waveform that represents sound directly. It shows air pressure changes
over time
Frequency-domain display - CORRECT ANSWER - a line spectrum that shows the
frequency components of a periodic sound(at 1 particular point in time). Frequency is on the X
axis and amplitude is on the Y.
3D spectrogram features [what are the three dimensions?] - CORRECT ANSWER - X axis
=time Y axis =frequency darkness =intensity
Exam Questions and CORRECT Answers
4 features of the scientific method: - CORRECT ANSWER - empirical, deterministic,
predictive, parsimonious
Octave - CORRECT ANSWER - a doubling or halving of a frequency
How many semitones in an octave? - CORRECT ANSWER - 12. each semitone is a non-
linear step in terms of # of Hz from one semitone to the next. However, they all sound equal to
us.
Sampling rate - CORRECT ANSWER - The number of snapshots of the sound in time. (
in Hz) 10 samples is a 10 Hz recording. Generally, the higher the sampling rate, the higher the
fidelity of the recording. Graphic representation of the join the dots graph, the more dots, the
better the image, the fewer, the cruder. A higher sampling rate will take up more space and
require higher processing power.
Nyquist frequency - CORRECT ANSWER - half the sample rate. You determine the
highest frequency you want to include in your recording and double it, this will ensure that the
playback will go at least as high as the original signal. Nyquist determines the highest frequency
you can reproduce in playback. CD sampling rate is 44,100 and it stores signals up to 22,050 Hz.
Aliasing - CORRECT ANSWER - When sampling too slowly, you will inaccurately
record the original signal. High, original frequencies will be improperly recorded as lower
frequencies. Think of the sine wave, where only certain dots were captured, so the original
waveform is "smoothed out" or aliased.
How to prevent aliasing - CORRECT ANSWER - This can be prevented with a low pass
filter at the nyquist frequency, to keep out the high frequencies that might be misrepresented.
High pass filter - CORRECT ANSWER - allows high frequencies and attenuates low
frequencies
, Low pass filter - CORRECT ANSWER - allows low frequencies and attenuates high
frequencies
Band Pass filter - CORRECT ANSWER - Removes high and low frequencies but lets
through the frequencies in the middle
Band reject filter - CORRECT ANSWER - Allows all frequencies except for a specific
band in the middle.
Fourier transform - CORRECT ANSWER - a way to analyze complex sounds by
separating them into their components
How to do a Fourier transform - CORRECT ANSWER - You take a time domain wave
form ( microphone signal - time on x and amplitude on Y) you apply the fourier transform to it
and it gives you a frequency domain wave form ( line spectrum) which represents a slice in time
that has frequency on x and amplitude on y. It's like parsing light through a spectrum which
shows all of the colors. So you can now hear all of the individual sounds that make up the
harmonic series - this is the spectrum / frequency/domain display. Similar to a list of ingredients
of a cake.
time-domain display - CORRECT ANSWER - has time on the X axis and Amplitude on
the Y axis and shows a waveform that represents sound directly. It shows air pressure changes
over time
Frequency-domain display - CORRECT ANSWER - a line spectrum that shows the
frequency components of a periodic sound(at 1 particular point in time). Frequency is on the X
axis and amplitude is on the Y.
3D spectrogram features [what are the three dimensions?] - CORRECT ANSWER - X axis
=time Y axis =frequency darkness =intensity
