COMD 5070 Exam 3-Questions with Correct Answers/ Verified/
latest Version (2024/2025)
4 features of the scientific method: - ✔✔empirical, deterministic, predictive, parsimonious
Octave - ✔✔a doubling or halving of a frequency
How many semitones in an octave? - ✔✔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 - ✔✔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 - ✔✔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 - ✔✔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 - ✔✔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 - ✔✔allows high frequencies and attenuates low frequencies
Low pass filter - ✔✔allows low frequencies and attenuates high frequencies
, Band Pass filter - ✔✔Removes high and low frequencies but lets through the frequencies in
the middle
Band reject filter - ✔✔Allows all frequencies except for a specific band in the middle.
Fourier transform - ✔✔a way to analyze complex sounds by separating them into their
components
How to do a Fourier transform - ✔✔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 - ✔✔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 - ✔✔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?] - ✔✔X axis =time Y axis
=frequency darkness =intensity
3D spectogram. what does it show? - ✔✔it's a hybrid of time and frequency domain.
Showing how the strength in each range of frequencies is changing over time.. Dark lines
correspond to the higher peaks from the spectrum. White is minimal energy.
Y axis on a spectrogram is limited to - ✔✔the Nyquist frequency - because it is made from a
digital recording
latest Version (2024/2025)
4 features of the scientific method: - ✔✔empirical, deterministic, predictive, parsimonious
Octave - ✔✔a doubling or halving of a frequency
How many semitones in an octave? - ✔✔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 - ✔✔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 - ✔✔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 - ✔✔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 - ✔✔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 - ✔✔allows high frequencies and attenuates low frequencies
Low pass filter - ✔✔allows low frequencies and attenuates high frequencies
, Band Pass filter - ✔✔Removes high and low frequencies but lets through the frequencies in
the middle
Band reject filter - ✔✔Allows all frequencies except for a specific band in the middle.
Fourier transform - ✔✔a way to analyze complex sounds by separating them into their
components
How to do a Fourier transform - ✔✔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 - ✔✔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 - ✔✔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?] - ✔✔X axis =time Y axis
=frequency darkness =intensity
3D spectogram. what does it show? - ✔✔it's a hybrid of time and frequency domain.
Showing how the strength in each range of frequencies is changing over time.. Dark lines
correspond to the higher peaks from the spectrum. White is minimal energy.
Y axis on a spectrogram is limited to - ✔✔the Nyquist frequency - because it is made from a
digital recording
