Outer Ear Anatomy (2)
Pinna
Outer Ear Canal
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| Term | Definition |
|---|---|
| Outer Ear Anatomy (2) | Pinna Outer Ear Canal |
| Outer Ear Physiology (4) | Collect Sound Sound Pressure Gain (amplify middle frequencies 1-5 kHz) Sound Localization Protect Tympanic Membrane |
| Middle Ear Anatomy (3) | Tympanic Membrane 3 Auditory Ossicles 2 Middle Ear Muscles |
| 3 Auditory Ossicles | Mallues (Hammer) Incus (Anvil) Stapes (Stirrup) |
| 2 Middle Ear Muscles | Tensor Tympani Stapedius |
| Middle Ear Physiology | Sound Transmission -amplification in the middle frequency -3 mechanisms for impedance mismatch problems -protection of hearing: acoustic reflex (tensor tympani & stapedius) |
| 3 Mechanisms for Impedance Mismatch Problems | Area Ratio: the surface area ratio of the tympanic membrane to that of the stapes is 20:1, which allows the middle ear to amplify sound waves Lever System: the 3 ossicles act as a lever system that amplifies the sound waves received from the tympanic membrane Buckling of Tympanic Membrane: helps maintain the level of tension needed to ensure sound transmission to the inner ear |
| Acoustic Reflex of the Tensor Tympani and Stapedius | An involuntary muscle contraction in response to loud sounds to protect the inner ear. |
| Anatomy of Cochlea (4) | Three Scalae Two Membranes Helicotrema Organ of Corti |
| Three Scalae | Scala Vestibuli Scala Tympani Scala Media |
| Two Membranes | Reissner's Membrane Basilar Membrane |
| Organ of Corti | Inner and outer hair cells -auditory nerve innervations: many-to-one (IHC) and one-to-many (OHC) pattern |
| Cochlea Physiology (1;3) | Response of Basilar Membrane -Traveling wave of the Basilar Membrane -Frequency Selectivity -Intensity Resolution |
| Traveling wave of the BM | Displacement of BM caused by the flow of perilymph in the scala vestibuli and scala tympani |
| Frequency Selectivity | Tuning curve, characteristic frequency |
| Intensity Resolution | Non-linear compression at characteristic frequency |
| Organization of Auditory Nervous System (ANS) (3) | Auditory neuron and nerve Auditory brainstem Auditory forebrain |
| Auditory Neuron and Nerve Anatomy (3) | Type I auditory fiber Type II auditory fiber Spiral Ganglion |
| Auditory Neuron and Nerve Physiology (4) | Spontaneous firing and thresholds Tuning curve (frequency selectivity) Intensity resolution: threshold, saturation, and dynamic range Phase locking: up to 5 hKz only |
| Auditory Brainstem (4 Nuclei) | Cochlear Nucleus, Superior Olivary Nucleus, Inferior Nucleus, Media Geniculate Nucleus |
| Auditory Forebrain | Medial Geniculate Body Auditory Cortex |
| Psychoacoustics Definition | Combines acoustic and psychological features to understand how our brain understands sound |
| Three Auditory Tasks | Detection-the ability to hear the presence or absence of sound Discrimination-the ability to hear and distinguish between different sounds Identification-the ability to name what you hear |
| Psychoacoustic Methods (3) | Method of Limit Method of Constant Stimuli Scaling Method (direct scaling, ratio scale, magnitude scale) |
| Method of Limit | Involves presenting ascending and descending tones to a listener, who indicates whether they heard the tone, to determine the threshold of what they can hear. -adaptive -fixed step size -threshold=the average number of reversals, at least 7 -pros=quick and reliable -cons=data only comes around the threshold line |
| Method of Constant Stimuli | Involves presenting a fixed set of stimuli, each varying in a specific physical dimension, to a listener in a random order, who responds to each. The data is analyzed to determine the point at which a stimulus can be detected or two stimuli can be distinguished. -threshold=certain percentage point |
| Direct Scaling Method | Directly establishes the correspondence between physical sounds and their perception; loudness and pitch |
| Ratio Scale | Asks the listener to compare the magnitude of one sound to that of a reference sound |
| Magnitude Scale | Asks the listener to assign a numerical value to a sound based on how intense they perceive the sound. -no reference sound |
| Auditory Masking Definition | Interference that one sound stimulus causes on the perception of another |
| Auditory Masking Efficiency | The effectiveness of a masking sound in obscuring the perception of a target sound |
| What can be maskers? | Static sound: sounds that do not change over time, white noise, pink noise, pure tones Dynamic sound: sounds that change over time, ambient noise, soundscapes |
| Tonal Masking | Masking efficiency is dependent on the intensity level and frequency of the tonal masker |
| Auditory Filter Definition | Describes the frequency selectivity of the human auditory system. Frequency-dependent masking suggests that only those frequencies close to the signal frequency are effective in masking |
| Auditory Filter Bandwidth | The critical bandwidth is the range of frequencies within which a second tone will mask the perception of the first tone. -measures notch noises (a dip in hearing sensitivity at specific frequencies) -relationship with frequency selectivity, broader tuning curve=more interference and causes spectral smearing problems -affecting factors: signal level and hearing status |
| Loudness | Attribute of auditory sensation in terms of which sound can be ordered on a scale from quiet to loud |
| How to measure loudness | Matching method=listeners adjust the level of the sound to match the loudness of the reference sound Scaling method=listeners scale the loudness level of the sound relative to the reference sound (very soft, soft, loud, very loud) |
| Loudness growth function | Loudness recruitment=phenomenon where the perception of loudness increases with the intensity of the sound |
| Factors affecting loudness (3) | Intensity level Frequency Duration |
| Pitch Definition | Attribute of auditory sensation in terms of which sounds may be ordered on a musical scale |
| How to measure pitch | Matching method=listeners are asked to adjust the frequency of the sound to match the pitch of the reference sound Scaling method=Listeners are asked to scale the pitch value of the sound relative to the pitch of the reference sound -reference sound: 1 kHz tone defined to have a pitch at 1000 mel –hard to measure due to the complexity of pitch |
| Missing Fundamentals of Complex Tones (combo of multiple frequencies) | Listeners can perceive a pitch for complex tones that do not have any spectral components (fundamental frequencies and their harmonics) at the perceived pitch |
| 2 Theoretical Models of Complex Tones | Envelope-periodicity theory Spectral-location theory |
| Envelope-periodicity theory | Suggests sounds with the same fundamental frequency can produce the same pitch, regardless of waveform or frequency composition, as long as they have the same envelope frequency (amplitude and frequency changes over time) |
| Spectral-location theory | Suggests sound localization (the brains ability to determine the location and origin of complex sounds) is based on the spectral distance between tones |