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Sound Ranges of Hearing Frequency / Wavelength / Period / Speed

AUD202 Audio and Acoustics Theory. Sound Ranges of Hearing Frequency / Wavelength / Period / Speed. What You Need to Learn Today. What sound is and how it travels The frequency range (Hz) and dynamic range (dB) of human hearing

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Sound Ranges of Hearing Frequency / Wavelength / Period / Speed

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  1. AUD202 Audio and Acoustics Theory Sound Ranges of Hearing Frequency / Wavelength / Period / Speed

  2. What You Need to Learn Today What sound is and how it travels The frequency range (Hz) and dynamic range (dB) of human hearing How to calculate frequency, wavelength, period and speed of sound

  3. Acoustics: the physics of sound Psychoacoustics: the human perception of sound

  4. Sound is Vibrations When an object vibrates it causes nearby molecules to vibrate causing a chain reaction

  5. Sound is Vibrations Sound travels as a series of compressions and rarefactions through a medium

  6. Sound is a Mechanical Wave Sound travels through air as a longitudinal wave However it can also travel as a transverse wave (such as on a guitar string or a wave in water)

  7. One complete cycle is one compression and one rarefaction 1 cycle per second = 1cps = 1 Hertz = 1Hz

  8. Frequency range of hearing The human ear is capable of hearing frequencies between 20 and 20,000 cycles per second (20Hz to 20kHz)

  9. Frequency range of hearing 10kHz 15kHz 16kHz 17kHz 18kHz 19kHz 20Hz 40Hz 80Hz 100Hz 150Hz 200Hz

  10. Dynamic Range of Hearing The typically accepted amplitude range of human hearing is 120dBSPL Sound amplitude is referenced to the Pascal (Pa) (the unit for pressure) 0dBSPL = 0.00002 Pascals (20µPa) 120dBSPL = 20 Pascals

  11. Dynamic Range of Hearing 60 decibels of amplitude -60dBFS to 0dBFS

  12. Sine Wave The sine wave is a pure tone with no harmonics. It is a ‘simple waveform’ 1kHz sine wave

  13. Other Simple Waveforms Sine Square Triangle Sawtooth

  14. HIGHER FREQUENCY shorter wavelength LOWER FREQUENCY longer wavelength

  15. Characteristics of Waveforms Frequency (number of cycles per second) Wavelength (length of one cycle in metres) Amplitude (strength or power of the wave) Period (time for one cycle in seconds)

  16. = period of one cycle (in seconds) = frequency in Hertz(Hertz is cycles per second) = wavelength (in metres) = velocity of sound (in metres per second) Units of Measurement

  17. Velocity of Sound Formula The velocity of sound through air at 20 degrees Celsius is 344m/s

  18. What is the wavelength of 20Hz? Wavelength (m) = speed of sound / frequency (Hz) = 344 / 20 = 17.2 metres

  19. Frequency (Hz) = speed of sound / wavelength (m) What frequency has a wavelength of 1.72cm? f = 344 / 0.0172 f = 20,000Hz

  20. What frequency has a period of 2 milliseconds? frequency in Hz = 1 / period (in seconds) f = 1/.002 f = 500Hz ms = millisecds. There are 1000ms in 1 second

  21. period in seconds = 1 / frequency (Hz) What period has a frequency of 200Hz? Answer in milliseconds. T = 1/200 T = 0.005 seconds T = 5 milliseconds

  22. What is the speed of sound at 1,263,719°C? v = 331 + (0.6 x 1,263,719) v = 758,562.8 m/s

  23. The Sound Barrier

  24. The Sound Barrier

  25. Velocity of Sound in Various Mediums Air > 344 m/s Hydrogen > 1284 m/s Water > 1482 m/s Human Brain > 1540 m/s Gold > 2000 m/s Steel > 5200 m/s Diamond > 12000 m/s

  26. Speed of Sound Through Air Calculate the speed of sound at: 0°C 5°C 10°C 20°C 30°C v = 331.4 + (0.6xC)

  27. Answers 0°C = 331.4 m/s 5°C = 334.4 m/s 10°C = 337.4 m/s 20°C = 343.4 m/s 30°C = 349.4 m/s

  28. What are the frequencies of the following wavelengths? 3.4m 5m 50cm 80cm

  29. Answers 3.4m = 101 Hz 5m = 68.8 Hz 50cm = 688 Hz 80cm = 430 Hz

  30. Calculate the Wavelength of: 140Hz in air (at 344m/s) 400Hz in steel (at 5000m/s) 500Hz for an electrical signal in wire (at 300,000km/s)

  31. Range of Hearing The ‘accepted’ range of hearing of a young undamaged ear is 20Hz to 20kHz The typical amplitude range is 120dBSPL

  32. The Decibel The Bel is named after Alexander Graham Bell 1847 –1922. The decibel (dB) is a tenth of a Bel In audio, amplitude is measured in decibels

  33. Loudness is Subjective Amplitude is Objective

  34. Loudness Loudness is a subjective term describing the strength of our perception of sound. Loudness is measured in Phons

  35. Threshold of Pain 120dB Threshold of hearing is

  36. To Recap Sound is audible pressure variations which travel as a series of compressions and rarefaction through a medium. Sound is a mechanical wave which is transmitted as longitudinal and transverse waves.

  37. Audio Engineering Society www.aes.org Username: jmcacademy Password: student1

  38. Papers related to NIHL on AES website Hearing Loss from Noise and Music Sound Pressure Levels in Symphony Orchestras and Hearing How the Ear Works and Why Loud Sounds Cause Hearing Loss Preventing Hearing Loss Investigation of the Loud Music Exposure Hearing Loss

  39. Moodle Key to enrol in Trimester 1 classes amplitude

  40. Next Week Wave Interaction Beat Frequencies Phase Concepts Comb Filtering Waveforms Noise

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