~Chapter 11 - Lecture Section 11.1 Flashcards
What is the physical description of sound?
Pressure changes in the air (or other physical medium, like water)
What is the perceptual description of sound?
The experience of hearing. Perceptually, we experience these vibrations as a sense of hearing.
We hear ___. First, the ___ vibrate, then the ___ vibrate, then our ___ vibrate.
vibrations // objects // air molecules // eardrums
What is condensed/compressed air?
An object moving/vibrating causes all the air molecules directly in front to be bunched up, a bit like a snow shovel compacting the snow into itself.
This compression causes all of these air molecules to bump into these other air molecules.
Do photons and sound/air molecules travel the same way?
No
How do sound/air molecules travel?
They bump into each other and transfer their kinetic energy.
The pushing out of the speakers diaphragm is then followed by a pulling inwards of the speakers diaphragm which creates a large area of space for a small number of molecules, and so this creates almost like a vacuum, where it is referred to as ___.
Rarefied Air/Negative Pressure
What is Rarefied Air/Negative Pressure?
Rarefied Air/Negative Pressure creates an area of low-density
When you have compressions followed by rarfraction/rarefied air, what you get are ___ of pressure where there is alternation between ___ and ___, and they propagate outwards away from the sound-source and all that kinetic energy of these air molecules bouncing off each other in a wave-form will eventually reach you ear, and it will cause vibrations on your eardrum, and this is where we get to the perceptual aspect.
longitudinal waves // rarified // condensed air
What are the simplest sound-waves?
Pure Tones
A Pure Tone is defined as a ___ wave.
sinusoidal
The sinusoidal transition between maximum pressure and minimum pressure creates a ___.
Pure Tone
If we’re making a graph for Pure Tone, and plot time on the X-axis and pressure on the y-axis, we have a Sine wave, where at the peak it represents the ___, so this is the condensation/compression of air molecules at some amplitude. At the ___ we have the lowest pressure/the rarefication of the air molecules.
highest pressure // bottom
Pure Tones can vary in ___.
Amplitude
What is Amplitude?
The difference in pressure between the highest part of the peaks and lowest part of the troughs/peaks of the wave.
Perception of Amplitude is ___.
loudness
What is a Decibel (dB)?
Decibel is the physical measure of sound intensity. Decibel is a measure of magnitude, and is used as the measure of Amplitude.
What is the formula for Decibels?
dB = 20 × log^10(p/po this is the standard pressure) (measured in Micropascals)
If standard pressure is ___ Micropascals, then this is referred to as the ___.
20 // Standard Sound Pressure Level (SPL)
What is a benefit of the formula for Decibels?
Because the formula for Decibels include this logarithmic calculation the decibel measure covers a large range of sound pressures in a manageable scale and corresponds to the non-linear perception of loudness that we have
What range of pressures can be covered by the Decibel (dB) scale?
There is a huge range of the Relative Amplitude going from barely audible (threshold) to giant sounds (spacecraft launch at close range) in Micropascal pressures is captured by the very manageable Decibel range of about 160.
The range of pressures that can be covered by the Decibel (dB) scale is ___.
0-160
Pure Tones can vary in ___.
Frequency
How is Frequency measured?
In cycles per second: in Hertz (Hz)
Frequency = 1 cycle/period
The highest Frequency has the ___ period.
lowest
The lowest Frequency has the ___ period.
longest
Frequency is the ___ of the period, the longer the period, the ___ the frequency.
inverse // lower
Frequency is somewhat linked to the perception of Pitch, such that lower frequency sounds are often perceived as ___ pitch, and higher frequency sounds are often perceived as ___ pitch.
lower // higher
Often, when we are considering the perception of Pitch, it’s useful to think about ___.
musical notes
Musical notes can be described by their ___.
Tone Height
What is Tone Height?
Tone Height is the perceptual experience of increasing pitch as sound frequency increases. It is more intricate than just low keys and higher keys on a piano
We are able to group certain ___ together.
Frequencies
On a keyboard, the notes A, B, C, D, E, F, G repeat, and notes of the same letter sound similar, they are said to have the same ___. Notes of the same letter have the same ___.
Tone Chroma // Tone Chroma
With a Tone Chroma, what we appear to be keeping track of perceptually is the ___ of ___ in these notes.
doubling // frequencies
The difference in frequency in A1, A2, A3, A4, ect, is that the frequency ___ as you go up each set.
doubles
A1 has ___Hz frequency
A2 has ___Hz frequency
A3 has ___Hz frequency
A4 has ___Hz frequency
27 ½ // 55 // 110 // 220
The frequency doubling as you go up a set in notes is referred to as an ___.
Octave increase
Musical Notes are described in ___.
Octaves
What is the formula for an Octave?
fOctave(n) = fbase* ^2^(n)
Notes of the same ___ have frequencies that are an ___ apart.
Tone Chroma // Octave
Both ___ and ___ will affect the perception of loudness
Frequency // Intensity
What is the Threshold of Feeling?
This is from when you stop hearing a sound and start feeling it vibrating through your body.
Any intensity below the ___ is inaudible, and just above it is barely audible.
Audibility Curve/Threshold of Hearing
What is an Equal Loudness Curves
Sounds that are relatively the same in dB and Hz would have an Equal Loudness
What animals can hear higher frequencies than us?
Dogs, Dolphins, and Mice
A dog whistle makes frequencies around ___Hz.
30,000
Elephants have a range of hearing that goes to very ___ bands, ___ than what humans can detect, and this is referred to as ___.
low // lower // Subsonic Communication
The Amplitude of a Pure Tone is mostly related to the ___.
perceived loudness
The Frequency of the tone is mostly related to the ___.
perceived Pitch
Pure tones are ___ tones, and realistic tones are more ___.
simple // complex
The perceptual quality of sound that can be directly related to its physical nature is ___, ___, and ___.
Sound Quality/Timbre // Loudness // Pitch
All the other properties of sound except for Loudness and Pitch will constitute ___.
Timbre
Most of our auditory experience is of ___ tones/sounds.
complex
We don’t usually hear ___ at all in our natural environment
Pure Tones
A ___ is the closest thing to an instrument that makes a Pure Tone.
Flute
What is Additive Synthesis?
The summation of multiple Pure Tones to make up Complex Tone.
Multiple Frequencies making up Complex Tones is an example of ___.
Additive Synthesis
Periodic Complex Tones such as musical notes that are played are made up of multiple ___.
Pure Tones
The first tone of a Harmonic is the lowest frequency, this is referred to as the ___.
Fundamental/First Harmonic
In Harmonics, the Second Harmonic is ___ times the frequency of the ___.
double // Fundamental
In Harmonics, the Third Harmonic is ___ times the frequency of the ___.
triple // Fundamental
In Harmonics, the Fourth Harmonic is ___ times the frequency of the ___.
quadruple // Fundamental
Adding Harmonics together produces a ___ and is an example of ___.
Complex wave-form // Additive Synthesis
Frequency, and the Amplitude of the Frequency produce a ___.
Frequency Spectra
What is the Periodicity Pitch?
The perceived similarity of tones that have the Harmonics removed
How is our auditory system able to achieve Periodicity Pitch?
In the Frequency spectra we see that all of the Harmonics have equal power, and creates that wave form → If we remove the Fundamental, now we only have Second, Third and Fourth Harmonics, the 200 Fundamental is removed. → The wave form between the original sound and the one that is missing the fundamental still has the same period, that is to say, the waveform is the smallest non-repeating unit. → The sound with the missing Fundamental has the same period before it repeats → What we have when we look at the frequency Spectra, we can see that the Fundamental Frequency is not only indicated by the power, but by the spacing of all of the subsequent Harmonics. → We can see in b that each of the subsequent Harmonics are spaced by 200Hz, therefore, we are able to reconstruct what the Fundamental should be.
How is it that the same note played by different instruments sounds the same tone height, but you can clearly distinguish a guitar from a piano?
This is due to the power of each of the Harmonics.
Even though the Fundamental Frequency of the G3 note is 196Hz, we can see that the pattern of Harmonics that are created in a guitar or busson or alt sax, they all have the same frequencies, but the ___ of the subsequent Harmonics is slightly different. This is the ___ of the different notes.
Amplitude // Timbre
What is Attack?
Attack of a tone is the buildup of sound at the beginning of the tone, so that it can start quiet and get louder and vice versa.
What is Decay?
Decay of a tone is the decrease in sound at end of tone. This can be very rapid or very gradual
Piano notes have a very rapid ___. If you play a note on a piano ___ it sounds like an ___.
Attack // backwards // Organ
What is a Periodic?
Periodic sound is a sound where the pattern of pressure changes repeats. These are the musical notes / Pure Tones we’ve been talking about
What is an Aperiodic?
Aperiodic sounds is where the pattern of sound waves does not repeat (e.g. door slamming or object dropping, crunch of a leaf, ect.)
___ sounds are what we mainly encounter outside of the time we are listening to music.
Aperiodic
