Wk 2 Flashcards
Pitch and Tuning
Pitch and tuning are musical terms that relate to the frequency of a sound.
For example, concert A is the musical note we now associate with a sound with a frequency of 440Hz.
Any sounds with constant and recognisable pitches, often due to their associated harmonics, can be organised into a tuning system.
Difference between Frequency and Pitch
Frequency is measurable–an objective description of wave property (Measured in Hertz (Hz or kHz)
Pitch is perception of frequency– subjective.
* The structure of the harmonics (individual partials, or waveforms components) gives us the perception of pitch.
What is the difference in frequency between octaves?
Each doubling of a frequency gives us the same note one octave up.
440Hz = concert A, therefore
880Hz = A one octave up
Ratios between pitches for
Octave
P5th
P4th
Maj3
2:1
3:2
4:3
5:4
Difference between simple and complex waves
Simple are continuous and repetitive in nature, one cycle looks exactly like the next
Complex represent practically all other sounds produced in music and nature. They almost never repeat and often are not symmetrical about the zero line.
Formula for sine wave
y=sin x
Sine wave
Frequency and Harmonic elements: Fundamental, no harmonics
A sine wave represents a single frequency with no harmonics and is considered an acoustically pure tone
“Pure” “Dull”
Sawtooth wave
“Buzzy” “Bright”
Frequency and Harmonic components: All Harmonics (even and odd)
Harmonic Amplitude: 1/Harmonic Number (1/1, 1/2, 1/3)
Even Harmonics 180 degrees Out of Phase
Square wave
“Hollow” (like woodwind instruments)
Frequency and Harmonic components: a fundamental sine wave and
odd harmonics of the fundamental (need at least fundamental and third
Harmonic Amplitude: 1/Harmonic Number (1, 3, 5, 7…)
Phase: All harmonics in phase
Triangle Wave
Frequency and Harmonic components: Only Odd Numbered Harmonics
Harmonic Amplitude: 1/Harmonic Number Squared
Higher frequency harmonics are lower amplitude.
Every Other Harmonic is 180 degrees Out of Phase
Decibel/Amplitude
Along with frequency (Hz), we also measure the amplitude of a waveform.
Amplitude is a measure of magnitude (size) of an audio signal and is essentially how loud a sound is. Consider this as intensity.
Sound Pressure Levels (SPL)
The acoustic pressure that’s built up within a defined atmospheric area (usually a square centimetre, or cm2). The higher the SPL, the louder the perceived sound.
Are usually expressed in deciBels (dB).
There are many data points when measuring amplitude, which result in large numbers.
* The human ear operates over an energy range of approximately 10^13:1
(10,000,000,000,000:1)
10 Trillion : one
Are Decibels absolute?
The dB is a ratio of a reference value to the value being measured.
It is NOT an absolute unit of measurement
Why do we look at decibels logarithmically
Our perception of a sound’s intensity is logarithmic. The deciBel is a logarithmic
ratio of two values.
We use logarithmic values to make very large and unwieldy numbers easier to manage. The dB allows for the expression of constant ratios between values and for the easy handling of very large values.
Because logarithmic numbers increase exponentially in a way that’s similar tobhow we perceive the doubling of loudness levels it expresses our perceived sense of volume more precisely than a linear curve
What is the harmonic series
The harmonic series consists of frequencies that are whole number multiples of the fundamental
frequency, and it is the balance of these harmonics that helps give sound a timbre.
What determines the perceived pitch?
The Fundamental Frequency
What determines timbre
The balance of component waves, including harmonic and enharmonic partials (F1 - F6)
How do we perceive loudness increase when -
Doubled
x10
x100
Moderate
Twice as loud
Four times as loud
How does SPL change with the square of the distance.
When a source-to-pickup distance is halved, the SPL level will be increased by
6 dB.
When doubled, the SPL level will be reduced by 6 dB.
Fletcher Munson explained
Demonstrates how we perceive some frequencies to be louder/richer than others
The low-frequency lines flatten out because at higher sound pressure levels the ear is more sensitive to lower frequencies. Notice how the ear is less sensitive to the frequencies above 6,000 Hz.
The Fletcher Munson Curves help explain why quieter music seems to sound less rich and full than louder music.
The louder music is, the more we perceive the lower frequencies, and thus it becomes more full and rich.
Amplitude envelope
Envelopes can be used to demonstrate any movement or change of a characteristic of sound over time.
We often refer to an envelope as the “shape” of the change of a parameter over time.
Attack
Sustain
Decay
Release
Attack
Decay
Sustain
Release
Attack – how long it takes the sound to
reach its maximum amplitude.
Decay – how long it takes to drop to the
sustain level.
Sustain – the level at which the sound
settles to.
Release – how long it takes for the sound to die away after energy has stopped being applied to the sound generator
How are the own dynamic
(amplitude) envelope of individual
harmonics (complex envelopes) represented
These complex envelopes can be represented via a spectrogram, which allows us to see how both frequency content and amplitude change
over time.
The way the amplitude of these individual
harmonics change over time contributes to determining a sound’s timbre.
