14 - Representing sound basics

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

  old fashioned




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

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

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

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

  both analogue and digital in nature

 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 CPU signals

  None of the above

  a set of waves

 4. What is the difference between analogue and digital recorded sounds?

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

  None of the above

  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

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

  bitling the sound

  ghosting the sound

  sampling the sound

  digitalising 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:




  internet router

 7. An input device senses incoming sound, it converts the sound into an electrical signal, and then this signal is ……..

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

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

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

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

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

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

  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 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

  They are both sound cards

  Analogue to Digital Converter and the Digital to Analogue Converter

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

  File opened. Binary numbers passed through the speakers directly

  None of the above

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

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

 11. Sound is measured in cycles per second or _______________________





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

  the higher pitched it sounds

  the quieter it is

  None of the above

  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)



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





 15. What is the sampling frequency or rate?

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

  None of the above

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

  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

  dim rate

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

  minimum bit rate (expected number of bits)

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

  140 KHz




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

  frequency information

  sampling keys

  binary bits

  multiple waves

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

  light vs sound dilemma

  accuracy of the measurement

  accuracy of the number of bits

  binary vs wave duality

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

  Sampling bit depth

  binary bit wave

  wave amplitude

  Accuracy of binary numbers

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

  worse than a lower one

  None of the above

  the same as a lower one

  better than a lower one

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

  less information is captured resulting in lower quality audio

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

  more information is captured resulting in higher quality audio

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

 23. Sampling resolution: In the diagram above, a sample can only have _____________ as represented by the 2 bit number

  three values

  four values

  two values

  eight values

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

  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 obliterate itself

   can handle the largest signal and the smallest signal,

  can handle only 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 = bit depth + number of channels + sample rate

  Bit rate = bit depth x channel rate

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

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

 27. Which of the following is the correct formula for bit rate?
a) Frequency × bit depth × channels = bit rate

b) Frequency × channels x bytes = bit rate

c) Frequency × bit rate x frequency x 2 = bit rate

d) Sampling size × bit depth × channels = bit rate





 28. The unit for bit rate is:

  samples per second

  bits per mile

  bits per second


 29. A CD quality stereo audio recording with two channels would require: Bit rate = 44,100 x 16 ______________

  x 3 = 150,22,2343 samples per second

  x 6 = 1882919281 bits per second

  x 20 = 2000,00021231 bits per mile

  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 small file sizes

  producing very quiet audio files

  producing very loud audio files

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





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

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

  take the bit rate and multiply it by itself

  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 sampling rate + bit depth

 33. Complete the formula:

  sample rate + bit rate + sample depth

  bit rate * 256

  length * sample rate

  bit rate * length

 34. Given the followig details, what is the storage requirement?

  2000 bits

  127 million bits

  3423 Hertz

  200.21 mebgabits

 35. As there are 8 bits to a byte, the storage for an uncompressed 3 minute CD quality recording is:

  bytes of storage = 100 / 2 = 50 Megabytes

  bytes of storage = 32 / 2 = 16 Megabytes

  None of the above

  bytes of storage = 127 Megabits / 8 = 31 Megabytes

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



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



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

  multiple / sony

  stereo / multiple

  configured / strero

  multiple / mentored

 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.

  none of the above


  all of the above


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



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



 42. Doubling the bit depth will ______________________________

  double the file size

  half the file size

  triple the file size

  None of the above

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



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



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