Frequency and pitch Flashcards
What is frequency?
The rate at which a regular event or vibration recurs in Hz.
What is the voice band for intelligible speech?
300 Hz to 3kHz
What frequencies surround sub bass?
Up to 60 Hz
What frequencies surround bass?
60-250Hz
What frequencies surround the mid-range?
250Hz-2kHz
What frequencies surround the high mids?
2kHz–6kHz
What frequencies surround the high frequencies?
6kHz-20kHz
What are low frequencies used in?
Used by synthesisers (LFOs), performers (vibrato, tremolo)
What is most real world sound made up of?
Multiple frequency components called partials.
What do pitched musical sounds contain?
A series of partials with frequencies that are integer relations of each other, called harmonics.
What is the fundamental frequency?
The lowest frequency in the harmonic series.
What is an overtone?
Any resonant frequency above the fundamental frequency.
Which harmonics does a saw wave contain?
All harmonics (1,2,3,4,5,6,7,8,…) in decreasing amplitude
Which harmonics does a square and triangle wave contain?
Only odd harmonics (1,3,5,7,9,…) in decreasing amplitude
How do the frequency and time domains differ?
The frequency domain considers audio from the perspective of frequency, rather than time - As opposed to the time domain (waveform) where we view audio as amplitude variations over time.
What can the frequency domain be used for?
Can be used to analyse, plot, process, or even store audio information (e.g. MP3).
What else can the frequency domain reveal details about?
Pitch and timbre (tone color / tone quality, e.g. piano, violin, etc.) - Plots often complex / difficult for humans or computers to interpret (e.g. automatic transcription)
What did Joseph Fourier propose?
- Any complex periodic signal could be represented as the sum of an infinite number of simple tones (i.e. sine waves of different frequency and amplitude)
- Complex sounds can be broken down into constituent frequency components
How can you ‘re-synthesise’ a sound?
Knowing all the (possibly infinite) frequency components of a sound, you could theoretically use a corresponding number of sine wave sound generators to re-synthesise it.
What does resynthesis allow you to do?
This allows us to change the frequency components independently of time (without affecting the duration of the sound).
What is pitch shifting?
Changes the pitch of audio without altering the duration (e.g. auto-tune, auto-harmonization)
What is time stretching?
Changes duration (e.g. tempo) without altering pitch.
What are vocoders?
They exploit the synthetic-sounding result of resynthesis as a musical effect.
Describe a spectrum analyser.
Very short segments used to provide a realtime animation of frequency bands. Can be useful for EQ’ing.
Describe a spectrum plot.
Analyses a longer segment of audio for precise frequency content, at the expense of time information.
Describe a waterfall plot.
- A Waterfall plot is a three-dimensional (3D) projection of time vs. frequency vs. amplitude.
- It combines both time and frequency domains.
Describe a spectrogram.
Plots time vs. frequency, using colour (or greyscale) to indicate the amplitude of frequency components.
What is pitch?
A subjective, perceptual quality of sound. It is based on pattern matching - recognising patterns of frequencies (rarely just one). Fundamental frequency of a harmonic indicates pitch.
Physiology of the ear: Pinna?
large area to receive and focus sound energy; collects sound… like a gramophone horn
Physiology of the ear: Auditory (or ear) canal?
Acts as a closed tube resonator, enhancing frequencies in the range 2-5 kHz (e.g. speech).
Physiology of the ear: Timpanic membrane (ear drum)?
Vibrates in sympathy with incoming sound … like a gramophone’s diaphragm.
Physiology of the ear: Ossicles?
Bones of the inner ear connecting the ear drum to the cochlea; transmitting / amplifying a stream of vibrations … like a gramophone stylus.
Physiology of the ear: Cochlea?
Converts vibrations to frequencies sent as electrical nerve impulses to the brain … like an electric pickup
What is the unit that measures loudness?
Phon
What represents the interval of an octave?
A ratio of 1:2 between two fundamental frequencies or (8ve).
What is consonance related to?
How ‘harmonious’ a note interval is (e.g. perfect 5th (2:3) or perfect 4th(3:4)).
How many cents are there in a semitone?
There are 100 cents in a semitone
- Therefore there are 1200 cents in an octave (octave is divided into 12 equal steps or semitones)
