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Human hearing

Human hearing. Limits, the human ear, and issues of perception. Physical Characteristics. Frequency range: 20 Hz … 20 kHz Factor of 1000 Intensity range: 10 -12 to 1 W/m 2 Factor of 10 12 Filtering of information. Physical characteristics.

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Human hearing

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  1. Human hearing Limits, the human ear, and issues of perception

  2. Physical Characteristics • Frequency range: 20 Hz … 20 kHz • Factor of 1000 • Intensity range: 10-12 to 1 W/m2 • Factor of 1012 • Filtering of information

  3. Physical characteristics Graphics: Rossing, Moore & Wheeler, The Science of Sound, 3rd Ed.

  4. Middle Ear: Transformation into mechanical and then electrical signals Psychophysics: • objective and quantitative study of the relation of physical stimuli and sensory perceptions Processing: sorting, selection, recognition Pressure fluctuations

  5. Structure of the human ear

  6. Important parts of the ear Outer Ear: • Auditory canal • Ear drum Middle ear: • Ossicles: hammer (malleus), anvil (incus), stirrup (stapes) Inner Ear • Cochlea • Auditory nerve

  7. Important parts of the Cochlea • Oval window • Scala vestibuli (filled with fluid) • Scala timpani • Round window • Basiliar membrane • Organ of Corti • Auditory nerve

  8. Mechanism of signal transport Hall, Musical Acoustics, 3rd Ed.

  9. Lever action of ossicles Small displacement over large area becomes large displacement over small area

  10. Hearing loss • Conduction deafness: reduced mobility of ossicles due to vibrous tissue (i. e. from repeated otitis) • Nerve deafness: deterioration of hair cells or nerve (also age-related presbycusis) • Can be distinguished through bone conduction

  11. Just noticable differences • At which frequency difference do two tones sound different to us? 200/201 Hz 200/202 Hz 200/203 Hz 2000/2002 Hz 2000/2003 Hz 2000/2004 Hz 2000/2006 Hz 2000/2008 Hz 2000/2002 Hz 2000/2003 Hz 2000/2004 Hz 2000/2006 Hz 2000/2008 Hz

  12. Simultaneous sounds • At which difference in frequency can we hear two distinct sounds? 1000 Hz combined with … 700 Hz 800 Hz 900 Hz 990 Hz 1010 Hz 1100 Hz 1200 Hz 1300 Hz 980 Hz 1020 Hz 950 Hz 1050 Hz

  13. How are sounds resolved?

  14. How are sounds resolved? • Critical band: region on basiliar membrane for reception of a pure tone • If critical bands overlap, only a single tone is heard • The critical band is larger at low frequencies.

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