Topic 4: Audio

Question 1

why does audio and sound important

Answer 1

add dimension to the multimedia application

Question 2

what is digitalize

Answer 2

convert sound wave into digital signal

Question 3

what and how to make digital sound

Answer 3

• microphone
• audio CD
• synthesizer

every sample is recorded and stored as digital information in bits and byte

Question 4

3 characteristics of digital audio

Answer 4

• frequency
• sound resolution
• channel

Question 5

define frequency

Answer 5

• sampling rate
• rate which sound is stored in sample per second or Hertz
• higher the frequency, clearer and sharper the sound

Question 6

define sound resolution

Answer 6

• number of bits used to represent each sample
• determine the quality of each sample

Question 7

types of sound channel

Answer 7

1. mono - flat and uninteresting
2. stereo - realistic and lifetime

Question 8

audio file size formula

Answer 8

file size = cstb

• c: channel (1 for mono, 2 for stereo)
• s: sampling rate in Hz
• t: time in second
• b: byte (1 for 8-bits, 2 for 16-bits)

Question 9

5 benefits of digital audio

Answer 9

• duplicate and edit with no loss of quality
• no wear and tear using CD as storage
• quality always same without noise
• can be integrated to other media
• random access

Question 10

difference between digital audio and MIDI

Answer 10

• digital audio play music and voice
• MIDI play only music

Question 11

what is MIDI

Answer 11

• Musical Instrument Digital Interface
• encoded scheme for recording and playing musical instruments on computer

Question 12

why did MIDI file size is small

Answer 12

• recorded only instruction and notes
• not the actual sound

Question 13

4 types of audio file

Answer 13

1. MPEG-2 Layer-2 (.mp3)
   - compress file size with minimum loss of quality
2. AIFF (.aiff)
   - apple
3. WAV audio (.wav)
   - used in most PC
   - large file size, best quality
4. Real audio (.ra)
   - stream audio while downloading