Lecture 47: Hearing 1 Flashcards
(22 cards)
What is sound?
Amechanical wave: vibrations that travel as longitudinal pressure waves
What is frequency?
Pitch (Hz)
What is amplitude?
Loudness (dB)
What is waveform?
Tone quality (timbre)
What does the ear convert?
Converts pressure waves into neural signals, allowing perception of pitch, loudness, and direction
What does sound require?
Vibrating particles in a medium
* No sound in space
* Travels faster in water (~1500m/s) than air (343m/s)
What happens to amplitude and frequency as sound travels?
- Amplitude decreases
- Frequencies remains the same - unless source of listener moves
What is 0db of sound?
Quietest sound a healthy adult can detect
What happens to loudness if there is +10dB increase?
Loudness doubles (2x)
What frequency can humans hear?
(Deep) 20 - (High) 20,000 Hz
What happens to the perception of loudness as the frequency increases?
Starts quiet, gets louder, gets quiet again
Name the 3 compartments of the ear:
- External ear
- Middle ear
- Inner ear
What structures make up the outer ear?
- Pinna: Reflect sound waves into auditory canal
- Auditory canal: Tube guiding sound to eardrum
- Tympanic membrane: Oscillates with sound
What is the role of the middle ear?
- Air-filled cavity connecting the tympanic membrane to the inner ear
- Converts air vibrations into mechanical movement
What structures make up the middle ear?
3 ossicles:
* Malleus (hammer)
* Incus (anvil)
* Stapes (sirrup)
* Smallest bones in the body
* Together act to amplify sound from ear drum to cochlea
What structures make up the inner ear?
Network of fluid filled tubes
* Cochlea
* Semicircular canals (vestibular system)
* Oval window forms one end of the cochlea and transmits vibrations from middle ear into the fluid filled cochlea
Describe the structure of the cochlea:
3 Chambers:
* Scala vestibuli: Receives vibrations from oval window
-> Reissner’s membrane
* Organ of Corti: Contains hair cells for sound transduction
-> Basilar membrane
* Scala tympani: Transmits vibrations toward the round window for pressure release
Describe the tuning of the basilar membrane:
Transmission of sound waves across the scala media causes basilar membrane to oscillate at a point along its length that’s in tune with the frequency of pressure waves
What effect do high pitch sounds have on the basilar membrane?
Cause the basilar membrane to oscillate at a point close to the oval window - stiff, narrow
What effect do low pitch sounds have on the basilar membrane?
Cause basilar membrane to vibrate closer to it’s apex - wide, flexible
What happens to the tuning of the basilar membrane at >5000Hz?
- Stiff mechanical properties of the basilar membrane near oval window
- Higher amplitude required
- Loss of phase-locking
What happens to the tuning of the basilar membrane at >200Hz?
- Longer distance of travel and loss of energy
- Higher amplitude required
