1.1 Music and Sound Flashcards
How is sound formed?
Through vibrations that require a medium to travel through.
What wave type does sound travel as and what happens?
Longitudinal, otherwise known as compression waves. In which a series of compressions (regions of higher pressure than the surroundings) and rarefactions (regions of lower pressure than normal).
What is a wavelength?
The distance between two successive compressions is one wavelength and the symbol is λ.
What is the frequency?
The number of vibrations per second or the number of compressions passing a fixed point per second and is measured in herts (Hz).
What equation links frequency and wavelength to wave speed?
c = f x λ.
Wave speed = frequency x wavelength.
What is infrasound?
Sound below 20 Hz is below human capabilities of hearing and known as infrasound.
What is ultrasound?
Sound above 20 kHz is above human capabilities of hearing and known as ultrasound.
When sounds are turned into an electrical signal, with a detector such as a microphone, how can the frequency be measured?
Using an oscilloscope. From the time-base setting the period (the time for one vibration, T) can be measured and hence the frequency (f) can be found using the equation. Period = 1/frequency
What is the time-base of an oscilloscope?
This is a circuit which controls how long it takes for the trace to cross the screen horizontally.
How is the pitch of sound from a musical instrument produced?
From the fundamental frequency plus harmonics.
What is a harmonic?
Multiples of the fundamental frequency.
What are sound waves of certain pitches that make a pleasant sound together known as?
Consonant or harmonics.
What do consonants/harmonic sound waves form the pass of?
Musical interval.
What is a musical interval?
An interval between two notes on a musical scale determined by the ratio of the frequencies of the notes.
What is quality sometimes called?
Timbre- it is an important factor that gives a musical instrument or voice its unique character.
What three aspects is the timbre of a sound made up of?
The harmonics present, the attack and decay of the sound and the vibrato.
How can harmonics be analysed?
Using Fourier analysis- this characterises the wave in terms of the different amplitudes of the frequencies that make up the harmonics of the sound wave.
How can harmonics be synthesised electronically?
Fourier synthesis- this is a process by which any regular sound can be reproduced by adding regular alternating voltages together.
What is the attack of sound?
A measure of how quickly it reaches its peak amplitude or loudness.
What is the decay of sound?
A measure of how long it takes to die away.
What is vibrato?
A periodic change in the pitch of the waveform as the sound continues to be produced.
What is a tremolo?
A name to describe a periodic change in amplitude- musicians will often do this deliberately to give expression or variation to music.
Middle C has a frequency of 256 Hz. What are the frequencies of the Cs which are one and two octaves higher than middle C?
512 Hz and 1024 Hz.
Define octave.
Musical interval between harmonics that have frequency f and 2f. Doubling/ halving of frequency.
