Perception 4

• What does the material suggest about the perception of loudness and pitch?

  It includes understanding how they relate to auditory input and how this input is coded by the auditory system
• How is sound defined perceptually?

  As the experience we have when we hear
• What is the physical definition of sound?

  Pressure changes in the air or other medium caused by the vibration of an object
• What is a pure tone?

  When changes in air pressure form a perfect sinusoidal wave
• What are the key characteristics of sound related to pure tones?

  • Amplitude: Size of variation in air pressure, related to loudness
  • Frequency: Number of cycles per second, related to pitch
• Why are most sounds in the world considered complex?

  Because they are combinations of sine waves
• What is the fundamental frequency?

  The lowest frequency of a sound wave
• What are harmonic frequencies?

  The highest frequencies of a sound
• What is the function of the pinnae in the outer ear?

  To funnel sounds into the ear canal
• What is the auditory canal?

  A tube-like structure around 3 cm long that protects the middle ear

  
• What is the tympanic membrane also known as?

  The eardrum
• How does the tympanic membrane respond to sound?

  It vibrates in response to sound waves inducing pressure differences
• What happens to larger amplitude sounds in relation to the tympanic membrane?

  They cause larger variations in the tympanic membrane's vibrations
• How do higher frequency sounds affect the tympanic membrane?

  They cause faster vibrations of the tympanic membrane
• What does the middle ear contain?

  The ossicles that amplify vibrations and transmit them to the oval window of the cochlea
• What is the malleus also known as?

  The hammer
• What is the incus also known as?

  The anvil
• What is the stapes also known as?

  The stirrup
• How do the ossicles function in the middle ear?

  They amplify the vibrations of the tympanic membrane and transmit them to the inner ear
• What is the main structure of the inner ear?

  The cochlea

  
• What happens when the oval window vibrates?

  It displaces fluid in the cochlea, causing a change in pressure
• What triggers auditory transduction in the inner ear?

  The motion of the basilar membrane
• How are neural signals generated in the Organ of Corti?

  By the bending of specialized hair cells
• What can overstimulation by loud sounds lead to?

  Damage to hair cells and hearing loss
• How is our perception of loudness related to sound waves?

  It is related to the amplitude of sound waves
• How are sound levels measured?

  On a logarithmic scale in units of decibels (dB)
• What does a change of 20dB represent?

  A ten-fold increase in amplitude
• How is sound amplitude coded in the auditory system?

  In the firing rate of auditory nerve fibers
• How do different auditory nerve fibers respond to sound intensity?

  Some fibers have high spontaneous rates and saturate rapidly, while others have low spontaneous rates and saturate slowly
• How does loudness depend on amplitude?

  It is not directly proportional; a sound must be increased by a factor of ~3.16 to be perceived as twice as loud
• How does loudness depend on frequency?

  Our auditory system is not equally sensitive to all sound frequencies
• What is the range of sound frequencies that humans can hear?

  From 20Hz to around 20,000Hz (20kHz)
• What does the U-shape curve indicate about human sensitivity to sound frequencies?

  It indicates poor sensitivity for especially low and high frequencies
• What is the place code in relation to sound frequencies?

  It refers to how sound frequencies cause vibration in specific areas along the basilar membrane
• Where do low frequencies cause vibrations in the basilar membrane?

  Near the apex
• Where do high frequencies cause vibrations in the basilar membrane?

  Near the base
• How is frequency signaled in the auditory system?

  By both when and how the auditory nerve fibers respond
• What is phase-locking in relation to auditory nerve responses?

  It refers to the synchronization of auditory nerve responses to changes in pressure
• What determines the pitch of a sound?

  The fundamental frequency of a sound
• What factors dictate the quality or timbre of a sound?

  The number, frequency ratios, and relative amplitudes of the harmonics