Manuel S Malmierca, M.D., Ph.D. University of … · combinan y forman una única onda compleja que...
Transcript of Manuel S Malmierca, M.D., Ph.D. University of … · combinan y forman una única onda compleja que...
35 000 a.C., Grubgrabenflöte First musical instrument
Hickmann & Eichmann (eds.) Archaeology of early sound production and tonal scales. Publikationen des Deutschen Archäologischen Institutes, Berlin (2003)
Sound and Sound propagation
Wave length
Soundpressure
Amplitude
Wavelength � c = � * � = 330m/s� = Frequency = number of cycles/s =Hz
Properties of a sine wave
• Frequency: Cycles per second, or Hertz (Hz). • Phase: angle (degrees).• Amplitude: decibels (dB)
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0
100
10pplog20
IIlog10SPLdB
• Relative
• Logarithmic
• Reference pressure p0 = 2x10-5 Pa
(hearing threshold 1kHz)
Decibel Scale
Measuring Loudness: The decibel scale
• Because the dynamic range of the ear is so great, sound amplitude is expressed on a ratio scale (log 10), not an interval (linear) scale.
• 0 dB corresponds the average human absolute threshold for hearing.
• A 6 dB increase corresponds approximately to a doubling of sound pressure.
�Far-range sense-- like the visual sense�Signals also invisible events
Essential for communication of animal and men�(speech; Helen Keller: “Being deaf is worse than being blind
blindness isolates from objects, deafness from men.”)
Hearing
La información que llega a los oídosno se puede separar y las ondas individuales se combinan y forman una única onda compleja que llegaal oído.
La información que llega a los oídosno se puede separar y las ondas individuales se combinan y forman una única onda compleja que llegaal oído.
¿Por qué las ondas de sonido simplemente no mueven directamente la membrana de la ventana oval?
¿Por qué las ondas de sonido simplemente no mueven directamente la membrana de la ventana oval?
Transformation:
Pressure pArea: Al : As = 17 : 1
Lever deflexion d : lm : li = 1,3 : 1
combined: d / p = 22 : 1
p / d = z * ���Impedance * Frequency
Function of the Middle Ear
The Cochlea, a three storied Snail-shell
Scala media
Scala tympani
Scala vestibuli
Corti-Organ
StapesIncus
MalleusTympanicmembrane
Oval window
Round window
Travelling waveenvelope
Travellingwave(Cord model)
Travelling wave in the Cochlea
Onda de desplazamiento
envolvente
+
=
The Fourier Analysis:
Is a mathematical method used to breakdown a complex periodical signal into its sinusoidal components
Frequency Analysis
440 Hz Fundamental
2 x 440 Hz (880) 2. Harmonic
3 x 440 Hz (1320) 3. Harmonic
440 880 1320Frequency
F Fourier-Spectrum
Am
plitu
de
Fundamental frequency ( 1. Harmonic):
Sine wave with the lowest frequency
Frequency Analysis
Stimulus propagation Amplification
Inner hair cell Outer hair cells
When depolarize the outer hair cells contract