1 / 16

Physiological and Physical Principles of the Human Hearing

Physiological and Physical Principles of the Human Hearing. Ossicles: Malleus Incus Stapes. Pinna. Labyrinth. Acoustical Nerve. Oval Window. Cochlea. Ear drum. Middle Ear. Oval Window. Eustacian Tube. Outer Ear. Middle Ear. Inner Ear. The Human Ear.

peckham
Télécharger la présentation

Physiological and Physical Principles of the Human Hearing

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Physiological and Physical Principles of the Human Hearing

  2. Ossicles: Malleus Incus Stapes Pinna Labyrinth Acoustical Nerve Oval Window Cochlea Ear drum Middle Ear Oval Window Eustacian Tube Outer Ear Middle Ear Inner Ear The Human Ear

  3. Middle Ear Capabilities 1) ImpedanceMatching between the sound impedance of air (400 kg*m-2*s-1) and the vibration impedance of the inner ear. (The impedance of water 3600 times higher: 1 480 000 kg*m-2*s-1) The impedance transformation is 1: 20 2) Protection from high sound levels: The acoustical reflex. The ossicles reduce the sound level by 6 –10 dB. This is known as temporaray hearing attenuation ofter hearing loud sounds.

  4. Outer Ear Capabilities Enables localisation in the meredian plane: Front, Back Above The localization depends on the spectrum of the sound: If other clues are missing, subjects will localize a frequency shaped noise as shown on the right: Maximum at 1 kHz: Back Maximum at 300 Hz and 3 kHz: Front

  5. Design of the Inner Ear Cut through Cochlea Inner Hair Cells 3 Rows of Outer Hair Cells Basilar Membran with inner and outer hair cells Hair cells in an electron microscope

  6. Mechanical Model of the Inner Ear Mechanical model of the Cochlea: Travelling waves in a box with a membrane of variable mass and stiffness High frequencies have their maximum at the beginning, low frequencies at the end of the cochlea.

  7. Inner Ear: Frequency Selectivity and Sensitivity The frequency selectivity and sensitivity of the human ear is several magnitudes better than expected from the mechanical model: At the hearing threshold the displacement of the basilar membrane is the size of a hydrogen atom only! Theory: The 90.000 outer hair cells are part of an active feedback amplification system. Hearing Impaired Author (Age 29) Neural Tuning Curve: Activity in the hearing nerve of a cat as response on tones of different level and frequency. Psychoacoustical Tuning Curve with hearing and discomfort level of the author and of a hearing impaired person

  8. Combination of Tones Modulation Two tones with a frequency distance of up to 15 Hz: Perception of modulation. Maximum is perceived at about 5 Hz: Modulation frequency of syllables A f Harshness Two frequencies having a frequency distance of 30-150 Hz: Perception of harshness. Maximum is perceived at 80-120 Hz A f Two Tones Two frequencies having a frequency distance of more than 150 Hz: Perception of two distinct tones. f

  9. The Ear: Technical Data Sensitivity: Hearing Level at 20 Pa corresponding to 10-16 W/cm2 . The displacement of the basilar membran is the size of a hydrogen atom only! Dynamic Range: 6 magnitudes, corresponding to 120 dB. Frequency Channels: 30.000 inner hear cells with filter slopes of 180dB/Oktave. Frequency Resolution: 3 Hz change at 1 kHz perceivable. Amplitude resolution: Logarithmic, 1 dB change is perceivable

  10. Block Diagram of the Neural Processing Simplified diagram of the auditory path for one cochlea (lower right). The top level shown is the primary acoustical cortex. Several connections between left and right brain regions are indicating significant binaural processing capabilities.

  11. Hearing Level, Curves of Equal Loudness • At low and high frequencies the hearing threshold rises. Otherwise we would hear our own blood flow. • Curves of equal loudness are modeled by A-, B- and C-compensation curves • At 120 dB, or 6 magnitudes beyond the hearing threshold is the pain threshold

  12. Frequency Groups A 2 kHz tone is presented in 10 falling amplitude steps of 5 dB. The tone is then masked with wide-band noise noise and noise with bandwith of 1000, 250 and 10 Hz. The spectral level of the noise is constant. When the bandwith is reduced the perceived loudness drops significantly. But only when the noise bandwith is smaller than a frequency group we can perceive more steps of the tone. Amplitude Frequency group bandwith Frequency Noise 1kHz bandwith noise 250 Hz band with noise 10 Hz bandwith wide-band noise

  13. The dB Scale The logarithmic loudness perception with wide band noise 10 steps with 6 dB attenuation (60 dB dynamic range) 15 steps with 3 dB attenuation (45 dB dynamic range) 20 steps with 1 dB attenuation. The smallest perceivable loudness change is 1 dB. Tracks 8-10

  14. Frequency Virtual Pitch On the phone (300 Hz to 3kHz) the fundamental of a speaker is not transmitted. We still can tell male and female speakers apart. A tone comples of 10 harmonics with a base frequency of 200 Hz generates the pitch sensation of the fundamental. Perceived pitch Initially the fundamental, then more and more harmonics are taken away. The pitch sensation changes only when just a few components are left over. Frequenz Empfundene Tonhöhe

  15. Virtual Pitch: Shepard‘s Paradox Ten octave tones are incremented in frequency. A weighting function allows to add new low tones without catching the attention. The effect is an ever increasing pitch. The second example demonstrates a decreasing pitch.

  16. Literature 1. SCHROEDER, M.R. Models of Hearing. Proc. IEEE, Vol63, No. 9, September 1975 2. MEYER, E., Neumann, E.G. Physikalische und Technische Akustik. ISBN 3 528 1 8255 5, Vieweg, 1974 3. ZWICKER, E. Schallrezeption am Beispiel höherer Säugetiere und des Menschen 3. ENGSTRÖM, H., ENGSTRÖM, B. Structure of the hairs on cochlear sensory cells. Hearing Research, 1 (1978) Elsevier/North-Holland Biomedical Press 4. LEWIEN, T. Filterung von Spracheinhüllenden zur Verständlichkeitsverbesserung bei Innenohrschwerhörigkeit. Dissertaton Göttingen, 1983. 5. KAY, R.H. Hearing of Modulation in Sounds. Physiological Revievs Vol. 62, No.3, USA, 1982. 6. SCHREINER, C., CYNADER, M. Basic Functional Organisation of Second Auditory Cortical Field (AII) of the Cat. Journal of neurophysiology, Vol. 51, No. 6, June 1984 7. ZWICKER,E., Fastel,H. Psychoacoustics. Springer 1990. ISBN 3-540-52600-5 8. KOLLMEIER, B. Script zur Vorlesung über physikalische, technische und medizinische Akustik. Oldenburg, 1999 9. HOUTSMA et al. Auditory Demonstrations. CD. Mit Heft. IPO, Philips, No. 1126-061, 1987.

More Related