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Audio unit

  1. 1. 1 of 29
  2. 2. What is Sound? Sound RecordingsSound Waves Digital MusicPitch Analog to DigitalThe Doppler Effect ConverterIntensity Factors Affecting theDecibel Scale Quality of a Digital RecordingLoudness Digital Audio Editing 2 of 29
  3. 3. Sounds are nothing more than waves of airpressure. We are able to hear sounds becauseour ears are sensitive to these waves ofpressure 3 of 29
  4. 4. A sound wave can be represented as awaveform which graphically describes theshape of the wave. 4 of 29
  5. 5. Click on each animation to learn about these two typesNon-PeriodicPeriodic 5 of 29
  6. 6. Page 1 of 2Sound that is created by a short, sudden event like a hand clap.The air that was between your hands is pushed aside increasingthe air pressure in the space near your hands. This increase inpressure occurs because more air molecules are temporarilycompressed into less space. The increased pressure pushes theair molecules outwards in all directions. When the pressurereaches your ear, it pushes on your eardrum causing you tohear the clap 6 of 29
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  8. 8. Page 1 of 2Sound created by a vibrationA good example of a periodic wave occurs when you ring a bell.After the initial strike (which is like a hand clap), the soundcomes from the vibration of the bell.When the bell is ringing, it vibrates at a particular frequency(depending on the size and shape of the bell) causing nearbyair to vibrate with the same frequency. 8 of 29
  9. 9. Page 2 of 2 Waveform for a typical bell vibrationWaves of air pressure travel outwards from the bell.Pressure waves from continuous vibration resemble the illustration. 9 of 29
  10. 10. Listen to the sound by clicking on the icon below the images, then click on the answers button ANSWERS 10 of 29
  11. 11. Wavelength describes the horizontal length ofone cycle of a wave or the distance from onepeak or trough to the next, as shown. Amplitude = height of the wave The higher the amplitude, the louder the sound 11 of 29
  12. 12. Sometimes referred to as frequency.Describes the number of waves that pass apoint in one secondCharacteristic of sound that makes it soundhigh or low. 12 of 29
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  14. 14. Pitch is measured in Hertz (Hz).The lower the pitch, the deeper the sound. 14 of 29
  15. 15. The audible range offrequencies (pitch)is usually between 20 Hz to20,000 Hz.There is considerablevariation between individuals,especially at the highfrequency end. 15 of 29
  16. 16. As a sound approaches, thepitch gets higher.As a sound moves away, thepitch gets lower. 16 of 29
  17. 17. Also known as “sound pressure level” (SPL).Measured in decibels (dB).• 0 dB = being completely quiet• 20 dB = whispering• 60 dB = normal conversation• 100 dB = mp3 player at its loudest• 110 dB = front row at a rock concert• 160 dB = instance perforation of eardrum 17 of 29
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  19. 19. The same sound will not be perceived to have thesame loudness to all individuals.• 20 dB = whispering • Elderly people might not hear you• 60 dB = normal conversation • Elderly people still might not hear you• 80dB = yelling at your grandpa! • He might finally hear what you‟re saying! 19 of 29
  20. 20. The same loudness measured in dB doesn‟tsound the same for everybody. 20 of 29
  21. 21. The first recorded sounds – 1860 and 1877 Click to read more 21 of 29
  22. 22. The first way that sound was able to be recorded. 22 of 29
  23. 23. Analog recordings are the opposite of digitalrecordings.Modern examples of analog recordings are: Vinyl records Reel-to-reel tapes Cassette tapes 23 of 29
  24. 24. To digitally record sound means that you recordit using a computer.The analog signal of a sound (sound waves) isconverted into a stream of discrete numbers thatrepresent the changes in air pressure over time. 24 of 29
  25. 25. Recording digitally has many benefits over analogrecording.• You can copy digital files as many times as you like without any loss of quality• You can burn digital files to a CD• You can share digital files on the Internet• You can edit the digital files more easily 25 of 29
  26. 26. • Music downloaded from iTunes and other places• Listening to Podcasts• Recording something using a microphone and your computer• Audio Books 26 of 29
  27. 27. The device used in digitalrecording.The ADC captures a „snapshot‟of the electric voltage on anaudio line.The „snapshot‟ is then CLICK TO ENLARGErepresented as a digital numberthat can be sent to a computer. 27 of 29
  28. 28. Sample rate Sample size• The rate at which • The number of digits samples are captured in the digital or played back representation of• Measured in Hertz, or each sample samples per second• An audio CD has a sample rate of 44,100 Hz (44 KHz) I STILL DON‟T UNDERSTAND! 28 of 29
  29. 29. We will be using Audacity to work with audio.To download Audacity, click on the icon, aboveYou are now ready to move on to the nextsection, “Working with Digital Audio” 29 of 29
  30. 30. Extra Slide #1
  31. 31. Extra Slide #2