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Science
Physics
COMD 3400 Section 1 Acoustics 3a - Based on Dr. Porters Lecture
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USU Lecture by Dr. Amy Porter Fall 2013
Terms in this set (41)
Simple Harmonic Vibrations are also referred to as?
As sine waves, pure sounds, or pure tones.
All of the wave forms in the picture are comprised of at least 2 different hertz frequencies added together. What is the wave called?
Complex wave.
It is assumed that all of the frequencies and amplitudes are the same.
Please note, that is not the case each time.
- There is no longer a pure tone but a complex sound.
T/F Complex wave forms change drastically depending upon the amplitude of its individual components?
True, the frequency of a wave in combination with the amplitude will cause that wave to resemble the frequency of the wave with the higher amplitude.
Define periodic sounds.
Sounds with a dominant frequency with a pure note or a pure tone.
a) Repeats itself over time.
b) Sound more musical
What is a complex periodic sound?
Those with dominant frequencies with multiple variable frequencies like a musical note are known as complex periodic sounds.
Define aperiodic sounds.
Noise: An is example of an Aperiodic sound
a. Frequency components not predictable
b. Sound composed of randomly varying frequencies.
Any frequency other than a harmonic frequency or complex frequency resulting disturbance of the medium is irregular, nonrepeating and would be termed Aperiodic.
A complex wave can have two types of sound, what are they?
a. Can be periodic or aperiodic in nature
b. Depends on individual sine waves contributing to the complex wave that is made.
Is the following picture a periodic or aperiodic?
Periodic wave, it repeats itself over time.
Is the following picture periodic or aperiodic?
This is aperiodic the wave doesn't repeat itself.
T/F Musical instruments and other objects vibrate in a regular periodic fashion and the harmonic frequencies are related to each other by simple whole number ratios = part of the reason such instruments sound pleasant.
True, harmonic frequencies are whole number multiples of F0.
The fundamental frequency is the __________________ __________________ _____ ___________________. The tone produced is the ______________ _____________.
lowest frequency of vibration
lowest tone.
T/F In a harmonic series from a periodic complex sound the frequencies are whole number multiples of the lowest or "fundamental frequency".
True
Define harmonic
Any whole numbered multiple of the fundamental frequency termed a harmonic.
If the first harmonic is 150 Hz list the 2nd - 4th harmonic.
1st Harmonic = 150 Hz
2nd Harmonic = 300Hz
3rd Harmonic = 450 Hz
4th Harmonic = 600 Hz
If you have the following harmonic ranges what are the corresponding overtones.
1st Harmonic = 150 Hz
2nd Harmonic = 300Hz
3rd Harmonic = 450 Hz
4th Harmonic = 600 Hz
2nd Harmonic = 300 Hz; 1st Overtone
3rd Harmonic = 450 Hz; 2nd Overtone
4th Harmonic = 600 Hz; 3rd Overtone
How is fundamental frequency of 300 Hz used to calculate the harmonics 1-5?
You multiply 300 x 1= 300 Hz 1st Harmonic
300 x 2 = 600 Hz 2nd Harmonic
300 x 3 = 900 Hz 3rd Harmonic
300 x 4 = 1200 Hz 4th Harmonic
300 x 5 = 1500 Hz 5th Harmonic, etc.
You multiply the fundamental frequency by the harmonic.
How is the octave generated in 300 Hz?
1st octave occurs when the fundamental frequency is doubled at the second harmonic of 600 Hz. The second octave occurs when 600 Hz is doubled = 1200 Hz or the 4th Harmonic, etc.
Do partials occur with overtones or harmonics?
Partials occur with each harmonic.
What does overtone denote?
Denotes any component in a complex tone that has a frequency higher than that of the fundamental frequency.
T/F All complex waves can be considered to consist of parts only?
False, all complex waves can be considered to consist of parts or partials.
Fundamental frequency is also the first harmonic = first partial
Second Frequency = second harmonic = second partial, etc....
Overtones and partials are numbered _____________.
differently.
Partials and harmonics are numbered the _______________.
same.
The lowest frequency component in a complex vibration or tone is
Fundamental Frequency
Overtone is defined as.
Any component of a complex tone having a frequency higher than that of the fundamental frequency.
Any component in a complex tone or complex vibration is a __________________.
Partial
What is a harmonic
A partial in a complex vibration, or a tone whose frequency is an integral multiple of the fundamental frequency.
Any interval of two frequencies having a frequency ratio of 2:1 an ___________________
Octave
It is said that one of the most amazing functions of the human ear is.....
its ability to resolve the varied frequencies that contribute to complex sounds.
The fundamental reason we are able to distinguish compositions of frequencies such as those found in vowels or how we can distinguish between a flute and a harmonica playing the same note is due to......
our ability to resolve frequencies.
T/F We are able to distinguish on our own how many components contribute to a particular sound and exactly what frequencies contribute as well.
False, although ear is able to resolve frequencies successfully it is not able to tell us each individual frequency.
What is the method used to know what frequencies and amplitudes are precisely contributing to a sound?
Fourier Analysis.
Who discovered "Fourier Analysis"?
French mathematician and physicist, Jean Baptiste Fourier
• 1786-1830
• Studying heat - discovered complex waves are built up of harmonic sine waves
What did Fourier discover and what does the analysis allow?
-Any continuous, repetitive wave shape can be built up out of harmonic sine waves.
-in its variance, allows a complex acoustic signal to be broken down into its actual frequency components.
What does Fourier Analysis reveal about tone?
Result of mathematical technique can reveal whether a sound is a pure tone containing only one frequency or a complex tone which would consist of multiple sine waves.
Wave forms can be represented on what type of graph?
Spectrum graph
Shows: • Amplitude, frequency and phase (single sinusoid)
Also could show the starting phase of each wave, not shown above.
What does Fourier Analysis tell us?
Mathematical technique to determine how much of each harmonic was present in the wave
• Acts like a prism
Musical tones for the most part are what types of tones?
Complex tones, composed of a fundamental frequency and harmonically related series of overtones
What type of sounds is speech composed of?
Transient sounds usually aperiodic in nature.
When are transient sounds generated in speech?
Are generated when a vowel is abruptly terminated by the articulators or any other type of abrupt type sound.
What are vowels composed of?
Vowels in speech are also composed of this fundamental frequency and harmonically related overtones.
An important characteristic of speech worth noting is that....
it is rarely in a steady state. We are not holding out vowels consistently and speech is constantly changing.
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