Ch. 10 and 11 Flashcards
two potential types of information for determining the source of a sound (auditory localization cues)
- pressure waves of sound do not reach both ears at the same time → sounds arrive very slightly sooner at the ear closer to the source
- The intensity of sound is greater at the ear closer to the source
interaural time difference (ITD)
the difference in time between arrivals of sound at one ear versus the other
azimuth
the angle of a sound source on the horizontal plane relative to a point in the center of the head between the ears; measured in degrees, with 0 degrees being straight ahead; angle increases clockwise toward the right, with 180 degrees being directly behind
medial superior olives (MSO)
a relay station in the brainstem where inputs from both ears contribute to detection of the interaural time difference; first places in the auditory system where inputs from both ears converge
interaural level difference (ILD)
the difference between levels (intensities) of sound at one ear versus the other
properties of ILD
- Sounds are more intense at the ear that is closer to the sound source and less intense at the ear farther away from the source
- The ILD is largest at 90 and -90 degrees; it is nonexistent at 0 degrees (directly in front) and 180 degrees (directly behind)
- Between these two extremes, the ILD correlates with the angle of the sound source but because of the irregular shape of the head, the correlation is less precise than it is with ITDs
difference between ITD and ILD
the head blocks high-frequency sounds much more effectively than it does low-frequency sounds
- ILDs are greatest for high-frequency tones
- ILDs are greatly reduced for low frequencies
lateral superior olive (LSO)
a relay station in the brainstem where inputs from both ears contribute to detection of the interaural level difference
cone of confusion
a region of positions in space where all sounds produce the same time and level (intensity) differences (ITDs and ILDs); extends perpendicularly from the left or right ear
pinnae and head cues
- Due to the shape of the pinna, they funnel certain sound frequencies more efficiently than others
- The size and shape of the rest of the body, especially the upper torso, affect which frequencies reach the ear most easily
- Due to these effects, the intensity of each frequency varies slightly according to the direction of the sound
anechoic room
room in which the walls are padded so that sounds do not bounce off the walls
measure how effects of pinnae and upper body shapes by having listeners sit in an anechoic room
- Anechoic room is filled with speakers at locations up, down, and all around the listener
- Insert microphones next to the person’s eardrums and play sounds from different points in space to measure how much energy from different frequencies actually reaches the eardrums from different locations
directional transfer function (DTF)
a measure that describes how the pinna, ear canal, head, and torso change the intensity of sounds with different frequencies that arrive at each ear from different locations in space (azimuth and elevation)
- as they grow, children may update the way they use DTF information
auditory distance perception
listeners are best at judging the distance to a sound source when it is about 1 meter away
relative intensity
- Cue for judging distance of a sound
- Sounds become less intense with greater distance
- Interpreting this cue requires one to make assumptions about the sound sources that may turn out to be false
- Inverse-Square Law
- intensity and movement work as a distance cue similar to motion parallax in depth perception because sounds that are farther away do not seem to change direction in relation to the listener as much as nearer sounds do
inverse-square law
a principle stating that as distance from a source increases, intensity decreases faster such that decrease in intensity is equal to the distance squared
spectral composition
Sound-absorbing qualities of air dampen high frequencies more than low frequencies, so when sound sources are far away, higher frequencies decrease in energy more than lower frequencies as the sound waves travel from the source to the ear
- analogous to the visual depth cue of aerial perspective
harmonic spectrum
the spectrum of a complex sound in which energy is at integer multiples of the fundamental frequency
- lowest frequency is the fundamental frequency
- perceived pitch is determined by the fundamental frequency and the harmonics add to the perceived richness of the sound
fundamental frequency
the lowest frequency component of a complex periodic sound (harmonic spectrum)
missing fundamental frequency in harmonic spectrum
If the fundamental frequency is removed from a series of harmonics and only the others are presented, the pitch that listeners hear corresponds to the fundamental frequency
timbre
the psychological sensation by which a listener can judge that two sounds with the same loudness and pitch are dissimilar
attack
the part of a sound during which amplitude increases (onset)
decay
the part of a sound during which amplitude decreases (offset)
auditory scene analysis
processing an auditory scene consisting of multiple sound sources into separate sound images
spatial separation between sounds
- Sounds that emanate from the same location in space can typically be treated as if they arose from the same source
- In a natural environment in which sound sources move, a sound that is perceived to move in space can more easily be separated from background sounds that are relatively stationary
- If sound stays in the same place relative to the path of a listener, it will be easier for that sound to be sorted out from other sounds (listeners can move)
spectral/temporal qualities
Sounds with the same pitch or similar pitches are more likely to be grouped as coming from the same source and to be segregated from other sounds
auditory stream segregation
the perceptual organization of a complex acoustic signal into separate auditory events for which each stream is heard as a separate event
similarity
Gestalt grouping rule stating that the tendency of two sounds to group together will increase as the acoustic similarity between them increases
grouping by timbre
When a sequence of tones that have increasing and decreasing frequencies is presented, tones that deviate from the rising/falling pattern are heard to “pop out” of the sequence