Assessed Discussion Flashcards
(20 cards)
What is a Membrane?
a thin material that cannot support its own weight so stretched across frame or cavity e.g drum head
What does excitation do to a membrane?
Sets up pattern of resonant modes, amplitude weightings dependant on type and position of excitation
What is a plate?
stiff and thick membrane that can support own weight - does not need to be under tension
What is an air collumn?
a tube where the diameter is very small compared to length, e.g flute/oboe
What is coupling?
How energy passes between a composition of air columns, strings, membranes, plates, air cavities
What is the proximity effect?
An increase in low frequency gain when microphone with directional pattern is close to a source
What four effects can the mic’s distance from a source have?
- Balancing relative level of direct sound from instrument and indirect sound (room reverb)
- Focusing on particular parts when close or picking up the whole instrument when distant
- Polar pattern related off-axis tonal colouration when distant
- Proximity effect when close
What is Excitation?
putting in energy to instrument (blowing, bowing, plucking, striking, scraping, rubbing etc)
What is resonance?
vibration of part of instrument due to excitation
What effects does resonance provide?
Shaping tonal character of sound
Amplifying sound so it is clearly audible
Extending sound in time
In a wind instrument, what affects the frequency?
the resonant modes of the air column, not the tube
Where are the nodes and antinodes in the first mode of an instrument?
Nodes at each end
Antinode in the middle
What is the nature of a resonator?
it can support multiple resonant modes simultaneously (with diff amplitudes)
What is the sum of the modes in a resonator?
The overall vibration of the resonator
What is sensitivity in relation to microphones?
the magnitude of signal produced for a particular amount of sound pressure
What is signal-to-noise ratio?
difference in decibels between wanted signal and noise produced by microphone circuitry.
How does an acoustic guitar produce sound?
The strings are either plucked or strummed to excite the instrument, the strings vibrations transfer energy into the modes in sound board via the saddle, the soundboard then vibrates the modes in the air inside the sound hole which produces the harmonics
How does a recorder work?
A recorder is excited by blowing into the the top, the harsh edge creates oscillating air and then the modes of the air column are vibrated by the excitation, the harmonics of the air column are the holes in the recorder, closing these holes can change the frequency of the sound (by shortening/lengthening the air column)
