Speech Science Exam 2

• What is an analog signal?

  speech sounds, musical tones, displacement of middle ear bones are all examples of analog signals
• What signal is continuous in time and amplitude?

  Analog signal
• what is the signal that can exist at every moment, and their amplitude at a particular moment can take on any value?

  analog signal
• This graph is an example of what signal?

  analog

  
• What is a digital signal?

  discrete-time signal( it only exists at discrete points; not continuously)
• Which signal analog or digital is not continuous and are digital "samples"?

  digital
• This signal exists at given moments only, and there is nothing in between what is it?

  digital signal
• This graph is an example of what signal?

  digital signal with discrete points

  
• Below is different examples of what specific signal, digital or analog?

  digital

  
• How are digital sound files better than analog tapes?

  • quality(copies identical to the original)
  • digital signals are more resistant to noise and degradation when transmitted than analog signals
  • data storage
  • the standard today
• What are examples of the incredible flexibility and efficiency of digital files to analog tape?

  • transferability(CD, HD,zip), file sharing via e-mail
  • accessibility to a computer or CD player
  • able to revisit any portion of your OG recordings quickly and easily
  • easy to transcribe
  • visual overview, no searching
  • more editing opportunities
  • randomization
  • can organize, rearrange and file
  • acoustic analyses
• Why does digitizing work?

  you trick your brain into hearing it even with a discrete number of data points that can be represented well where the digital signals sounds the same as the OG
• How does Analog to digital and digital to analog work?

  You get a representative sample and know how accurate the digital representation needs to be
• What does digitization mean?

  converting numbers(digits) so that the information can be stored in a numeric format
• Sampling and quantization are two main operations in what?


  digitzation
• What needs to be passed through before sampling and quantization occurs?

  a signal through a pre-emphasis filter and a presampling(low-pass) filter
• What filter boosts higher frequencies?

  pre-emphasis
• The presampling (low-pass)filter rejects the energy above what?

  the highest frequency of interest
• You should take samples at what type of intervals? (for analog to digital and digital to analog conversion)

  given
• a sampling rate of 10000Hz means the analog signal is sampled at how many times per second?

  10000 times
• Based on Nyguist's(1928) sampling theorem, how many samples are needed to have an acceptable sampling rate?

  twice the highest frequency of interest
• If a frequency is 5000Hz, what would the sampling rate have to be to match Nyguist theorem?

  10,000
• Why do we need a sampling rate of at least twice the highest frequency of interest?

  to avoid aliasing
• What is aliasing?

  a mock frequency of the original
• When does aliasing happen?

  when higher frequencies appear as "fake" lower frequencies due to lack of undersampling and the lack of low-pass filtering
• The graph below represents a regular frequency and an?

  Aliased

  
• How do you avoid aliasing?

  -determine the highest frequency of interest

  -filter the energy above the highest frequency of interest

  -sample the signal at a rate that is at least twice as high as the highest frequency of interest
• What is the recommended sampling frequency for speech applications?

  22,050Hz
• What converts the amplitude or energy level of the samples and the amplitude of the signal is made discrete and the continuous amplitude variations needed to be represented?

  quantization
• A______ is an increment of energy, what is it?

  quantum
• What is the quantization rate measured by?

  in bits
• The quantization rate is also measured by?

  bits
• how many levels does 1 bit have?

  2
• What is shown below?

  an outline of digital to analog conversion

  
• To listen to a recording, it needs to be converted to?

  analog form
• what is needed to smooth out the signal (eliminate the "steps" in the signal)?

  final low pass filtering
• Below is an outline of what?

  of A-to D and D-A conversion

  
• What does the time waveform present?

  the amplitude of the signal as a function of time
• What graph displays amplitude on the Y axis and time on the X axis?

  time waveform
• What is frequency?

  the number of times an object vibrates through a complete cycle per second; measured in Hz