COMD 5070 Exam correctly answered graded
A+
Frequency of a wave describes:
How frequently a waveform repeats
How many cycles per second
Related to number of vibrations of air molecules each second
Complex Waveform
contains multiple frequencies
Ex. Human voice
Decibels
Logarithmic because we don’t perceive linearly
Reference sound = The softest sound that will cause the eardrum to vibrate - 20
micro-pascals/threshold for hearing (0dB)
Digital Signals
Discrete in time and amp. (numbers = snapshots over time)
Presented by table of numbers
Analog Signals
Continuous in time and amp. (infinite number of points in time)
Presented by graph
Sampling Rate
Snapshots taken per second to create digital signal
Higher rate gives better fidelity and bigger file size
More gives better representation of original
Quantization
, Assigning a digital number to each amplitude value
Larger number = more detail
Smaller number = cruder detail
Nyquist Frequency
is half the sample rate
Need to sample at twice the rate of the highest frequency
Ex. Sample rate of 22,000 = 44,000
Spectrum (frequency domain)
Frequencies in waveform. Shows frequency components of a complex sound
X = Frequency
Y = Amplitude
Spectrogram
Shows how spectrums change over time
X = Time
Y = Frequency
Darkness = Intensity of Amplitude
Fourier Analysis/Transform
creates a spectrum by analyzing complex waveform
Presents all the different frequencies (ingredients)
Spectrum of a person’s voice:
Will have peaks (multiple frequencies)
Spread of energy in fundamental frequency and harmonics
A+
Frequency of a wave describes:
How frequently a waveform repeats
How many cycles per second
Related to number of vibrations of air molecules each second
Complex Waveform
contains multiple frequencies
Ex. Human voice
Decibels
Logarithmic because we don’t perceive linearly
Reference sound = The softest sound that will cause the eardrum to vibrate - 20
micro-pascals/threshold for hearing (0dB)
Digital Signals
Discrete in time and amp. (numbers = snapshots over time)
Presented by table of numbers
Analog Signals
Continuous in time and amp. (infinite number of points in time)
Presented by graph
Sampling Rate
Snapshots taken per second to create digital signal
Higher rate gives better fidelity and bigger file size
More gives better representation of original
Quantization
, Assigning a digital number to each amplitude value
Larger number = more detail
Smaller number = cruder detail
Nyquist Frequency
is half the sample rate
Need to sample at twice the rate of the highest frequency
Ex. Sample rate of 22,000 = 44,000
Spectrum (frequency domain)
Frequencies in waveform. Shows frequency components of a complex sound
X = Frequency
Y = Amplitude
Spectrogram
Shows how spectrums change over time
X = Time
Y = Frequency
Darkness = Intensity of Amplitude
Fourier Analysis/Transform
creates a spectrum by analyzing complex waveform
Presents all the different frequencies (ingredients)
Spectrum of a person’s voice:
Will have peaks (multiple frequencies)
Spread of energy in fundamental frequency and harmonics
