4.5: section 3: data representation: representing images and sound

Question 1

what is sampling rate

2 points

Answer 1

• the number of samples taken per second measured in Hertz

- increasing sampling frequency increases sound quality but also file size

Question 2

what is sampling resolution

2 points

Answer 2

• the level of detail recorded from an analogue signal
• the number of bits available for each sample
• n amount of bits provides 2^n combinations of colors or audio gradations

Question 3

equation for sound file sizes in bytes

Answer 3

sample frequency(Hz) x sample resolution(b) x time(s)/8

Question 4

what is MIDI (musical instrument digital interface)

Answer 4

-a standardised protocol, digital interface and connectors that allow digital instruments and computers to communicate

Question 5

what are event messages in MIDI used for

Answer 5

• event messages are stored in MIDI files
• these messages specify how an instrument should be played and what notes should be played
• include note duration, pitch, volume change, vibrato and temp synchronization

Question 6

what are the advantages of using MIDI files

6 points

Answer 6

• creates standardised way for musical sequences to be saved
• they can be used and shared across different devices and applications
• records instructions on how to play instruments rather than analogue sound so outside disruptions wont be recorded
• midi files can be up to 1000x more space efficient than other audio files
• allows for the easy manipulation of single instrument
• one midi artist can produce the same amount or work as an ensemble

Question 7

what is Nyquist theorem

3 points

Answer 7

• the sampling rate of sound should be at least twice the frequency of the highest frequency in the sound wave
• humans hearing frequency = 20-20,000 Hz
• audio sample rate should be at least 40,000Hz
• typical audio is sampled at 44,100 Hz