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12 - Representing Sound

 1. MP3 (formally MPEG-1 Audio Layer III or MPEG-2 Audio Layer III) is an audio coding format for __________ audio

  old fashioned

  digital

  metric

  clockword

 2. A "real" sound that we hear every day (like the sound of your friend's voice) is _____________

  (wave like) analogue in nature (tones and rhythms blend smoothly together)

  metallic in nature (in reality sound is made up of tiny metal bits)

  both analogue and digital in nature

  digital in nature (comprised of 1s and 0s)

 3. If a sound has to be handled by a computer any sound source has to be converted to ____________________

  a set of binary numbers

  a set of waves

  a set of CPU signals

  None of the above

 4. What is the difference between analogue and digital recorded sounds?
You do not need to watch the video to answer the question but to gain a more advanced understanding of this topic, it is worth viewing.

  An analog sound file is stored in bits where as a digital file is more advanced and wave like

  An analog sound file is less like the original sound as it is made up of digital bitcoins

  None of the above

  An analog signal is continuous, think: a wave. Digital refers to being stored in bits

 5. Digitising' the sound (making it digital) by using an input device connected to your computer is called:

  bitling the sound

  digitalising the sound

  sampling the sound

  ghosting the sound

 6. One device that is involved in capturing analogue sound and converting it into a digital file for use by a PC is a:

  microphone

  mouse

  modem

  internet router

 7. An input device senses incoming sound, it converts the sound into an electrical signal, and then this signal is ……..
Image Source: ICT Lounge
datarep_sound_q1.png

  passed on to the monitor to interpret the sound and record it directly

  passed on to the ADC (analogue to digital converter) in the sound card

  passed on to the operating system of the PC which will convert the sound into waves

  passed on to the CPU to convert the signal into binary bytes

 8. A sound card has two jobs. 1. Convert analogue signals to digital for storage and 2…….

  convert analogue signals into sound waves so the human ear can hear them

  convert digital signals into binary numbers so they can play accurately

  convert digital signals into 24 bit patterns which are read by the speakers

  convert stored digital signals into electrical signals to send to the speakers

 9. What are the ADC and DAC?

  They are both binary pattern sequences that are used to encode sound

  Neither of these exist

  Analogue to Digital Converter and the Digital to Analogue Converter

  They are both sound cards

 10. What needs to happen in order to play a sound (via a computer speaker)?

  File opened. Binary numbers fed through the ADC. Speakers use a sound card to re-convert to bits

  File opened. Binary numbers passed through the speakers directly

  File opened. Binary numbers fed through DAC. Amplification applied to power the speakers and play sound

  None of the above

 11. Sound is measured in cycles per second or _______________________

  Amps

  Watts

   Hertz

  Bits

 12. The higher the frequency (in hertz) the….

  the quieter it is

  None of the above

  the higher pitched it sounds

  lower pitched it sounds

 13. Tone is one thing, but loudness of sound also matters! Because sound is a ________, the loudness is the ________ of the wave

  height (amplitude)

  freight

  width

  depth

 14. ______________ is a method of converting an analogue sound signal into a set of binary numbers that are stored in digital format.

  bimping

  sampling

  amplituding

  frequenting

 15. What is the sampling frequency or rate?
Note: The following video is informative - do watch it if you can - but you don't need it specifically for this question.

  the rate at which sound is stored as waves and the length changes

  None of the above

  This is the rate at which samples are taken (stated in Kilohertz (thousand times per second)

  the rate at which binary sequences are converted into waves

 16. There is a _________________ at which samples need to be taken in order to faithfully reproduce the original signal

  maximum sampling rate

  minimum sampling rate (at least twice the highest frequency in the signal)

  dim rate

  minimum bit rate (expected number of bits)

 17. For a CD that has sound going up to about 20KHz, the minimum sampling rate is…
datarep_sound_q2.png

  20KHz

  140 KHz

  70KHz

  40KHz

 18. Getting the sampling rate right is important for capturing…..

  binary bits

  multiple waves

  sampling keys

  frequency information

 19. Another thing that is important to consider in this unit is the ______________

  light vs sound dilemma

  binary vs wave duality

  accuracy of the measurement

  accuracy of the number of bits

 20. The number of bits which are used per sample is called the:

  wave amplitude

  Accuracy of binary numbers

  Sampling bit depth

  binary bit wave

 21. Higher bit depth audio will sound …………………..
datarep_sound_q3.png

  better than a lower one

  None of the above

  worse than a lower one

  the same as a lower one

 22. As bit depth and sample rate increase…..
datarep_sound_q4.png

  the same amount of information is captured, which is why sound always sounds the same

  more information is captured, which causes blockage, and reduces audio quality

  more information is captured resulting in higher quality audio

  less information is captured resulting in lower quality audio

 23. Sampling resolution: In the diagram above, a sample can only have _____________ as represented by the 2 bit number
Image source: http://www.kierenreynolds.com
datarep_sound_q5.png

  four values

  eight values

  two values

  three values

 24. In the image below The 11KHz sound sample is far lower quality than the 44 KHz sample, but on the other hand …….
datarep_sound_q6.png

  the Khz is increased exponentially

  the number of bits per wave is reduced

  the file size is 30 times bigger

  the file size is 30 times smaller.

 25. Whenever a sound is sampled, you should ensure that the recording system________________otherwise the re-played sound will have some serious distortion.

  can handle only the smallest signal

  can obliterate itself

   can handle the largest signal and the smallest signal,

  can convert itself into bits

 26. The bit rate is the amount of information required to describe one second of sound. The formula is:

  Bit rate = sample rate x bit rate x sample rate x 2

  Bit rate = bit depth x channel rate

  Bit rate = bit depth + number of channels + sample rate

  Bit rate = sample rate x bit depth x number of channels

 27. To work out the bit rate for one second of audio you would have to:
Do the following to find out the bit rate for 
one second of audio: 
==================================================
Multiply the number of samples
taken in one second by the number of bits needed 
for each sample for each audio channel (then multiply 
by no. of channels)

TRUE OR FALSE?

  FALSE

  TRUE

 28. The unit for bit rate is:

  Hertz

  samples per second

  bits per second

  bits per mile

 29. A CD quality stereo audio recording with two channels would require: Bit rate = 44,100 x 16 ______________
The ideal sample rate
=====================
The sample rate of 44100Hz is standard
for music and CDs and is the
 ideal rate to record all your podcast 
audio at.

Note: Sound designers in game, film, and television 
will mainly work in 48000Hz, though some work 
as high as 96000Hz.

  x 20 = 2000,00021231 bits per mile

  x 3 = 150,22,2343 samples per second

  x 6 = 1882919281 bits per second

  x 2 = 1,411,200 bits per second (1.4 Mbps)

 30. The disadvantage of having a very high bit rate is ….

  producing very large file sizes

  producing very loud audio files

  producing very small file sizes

  producing very quiet audio files

 31. You can reduce the bit rate without sacrificing too much quality by using a technique called:

  meshing

  sacrificialsounding

  compression

  sampling

 32. To work out the total size of an audio file, you….

  take the bit rate and multiply it by the sampling rate + bit depth

  take the bit rate and multiply it by the number of bits contained in the file itself

  take the bit rate and multiply it by the length of the file in seconds

  take the bit rate and multiply it by itself

 33. Complete the formula:
file size = 

  sample rate + bit rate + sample depth

  bit rate * length

  bit rate * 256

  length * sample rate

 34. Given the followig details, what is the storage requirement?
Sampling rate: 44.1 Khz 
Sample bit depth: 16 bits; 
Recording time: 180 seconds

Storage = Sample rate x bit depth x channels x time
=

  200.21 mebgabits

  127 million bits

  2000 bits

  3423 Hertz

 35. As there are 8 bits to a byte, the storage for an uncompressed 3 minute CD quality recording is:
Sampling rate: 44.1 Khz 
Sample bit depth: 16 bits; 
Recording time: 180 seconds

Storage = Sample rate x bit depth x channels x time
=

  bytes of storage = 127 Megabits / 8 = 31 Megabytes

  bytes of storage = 32 / 2 = 16 Megabytes

  None of the above

  bytes of storage = 100 / 2 = 50 Megabytes

 36. (Most) humans use two ears to hear. A channel is a single sound stream.

  TRUE

  FALSE

 37. Mono sound has information about only a single source or single channel

  TRUE

  FALSE

 38. _____ sound will have ______ channels, to make use of multiple speakers. Each channel needs its own samples

  multiple / mentored

  stereo / multiple

  configured / strero

  multiple / sony

 39. In order for an audio player to play back a sound file, the file needs meta data (extra information) on top of the samples.
Which of the following in the list
count as basic meta data (embedded
at the beginning of the file)

1. Sample rate
2. Exact number of bits held
3. Bit rate
4. Name of the sampler
5. Length
6. Name of the device used to sample
7. Codec

  1,3,5,7

  none of the above

  1,2,3,4,5

  all of the above

 40. The longer the sampling lasts the smaller the file will be

  TRUE

  FALSE

 41. A bit depth of 8 bits allows 256 levels of the wave to be measured

  FALSE

  TRUE

 42. Doubling the bit depth will ______________________________

  triple the file size

  half the file size

  double the file size

  None of the above

 43. The higher the bit depth, the worse the percieved quality of sound.

  FALSE

  TRUE

 44. Bit rate (bits per second) is a product of sample rate, channel compression rate and four times the sample bit depth

  TRUE

  FALSE

 45. An uncompressed file format is WAV and a compressed format is a MP3

  FALSE

  TRUE