09 Introduction to Hearing(1)

09 Introduction to Hearing(1) - 1 Introduction to Hearing...

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10/25/2016 1 Introduction to Hearing WEEK 9 Lecture outline Sound Physical characteristics Perceptual characteristics Hearing Physiology of the ear Sensation Cortical Organization A1 Tonotopic map Sound Sound Sound is not out there Pressure waves “sound waves” ugh Air particles (but also, water, ground, anything that vibrates) Sound is our perception of those waves Transduction of pressure waves into electrical signals Temporal coding: Information is in the timecourse of sensation Sound: Physical properties Frequency Number of cycles in one unit of time Compression: ↑ pressure Rarefraction : ↓ pressure Hertz (Hz): Number of cycles in 1 second Amplitude Intensity or amount of change in pressure Micropascals ( μ Pa) Decibel (dB) 1 2 3 4 5
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10/25/2016 2 Compression & Rarefraction: Air Compression & Rarefraction: Water 44Hz Different frequencies Frequency Different Amplitudes Amplitude Different frequencies & ‘ tudes Decibel (dB) There is a wide range of audible pressure changes Decibel (dB) Different intensities can be orders of magnitude different If purring = 1 Talking = 10 Rocking = 100,000 Launching = 1,000,000 dB is a unit of measure that scales down the difference Logarithm Decibel (dB) dB = 20 x log 10 ( p / p 0 ) 20 = 20 log 10 = “logarithm of base 10” p = pressure of the wave (micropascals) p 0 = a reference pressure (usually 20 micropascals) Decibel (dB) dB = 20 x log 10 ( p / p 0 ) If an object creates pressure waves of 1000 micropascals: 6 7 8 9 10 11 12 13 14 15 16 17
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10/25/2016 3 dB = 20 x log 10 (1000/20) dB = 20 x log 10 (50) dB = 20 x 1.70 dB = 34 SPL Decibel (dB) dB = 20 x log 10 ( p / p 0 )
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