chap. 6 (hearing)

Dynamic range

difference between absolute threshold and pain threshold -humans absolute threshold most sensitive to frequencies between 1000-5000 Hz

intensity difference

difference between ear receiving more direct sound and other ear receiving more shadowed sound -greatest occurs when the sound source is at 90 degrees azimuth

time difference

difference between when the sound energy strikes the ears

acoustical pitch

measured in Mels

sound localization

nuclei in superior olive respond to differences b/c it's getting input from BOTH ears

Mel

subjective unit of equal distance separating pitches -one unit of equal distance of change -larger for bass sounds and small for treble sounds

aging

we lose the detection of higher frequencies first

place theory

-different areas of the basilar membrane vibrate differently b/c of shape and stiffness of the different areas (treble at base and bass at apex) -"place" indicates pitch -sharpening along basilar membrane so auditory hair cells outside of peak tend to be inhibited a little 1-high freq. selectively vibrate the basilar membrane of the inner ear near the oval window 2-low freq. travel further along the membrane before causing excitation 3-pitch determining mechanism is based on the location (PLACE) along the membrane where the hair cells are stimulated

frequency theory

-pitch is determined by overall frequency of spiral ganglion neurons firing together or in concert -"frequency" indicates pitch -WHOLE basilar membrane is vibrating->causes increase/decrease in overall output from spiral ganglion neurons Issue? this indicates we cant hear pitch above 1000hz because the neurons don't fire faster than that but WRONG because humans can hear up to 20000 htz

equal loudness contours

-shows the sound pressure levels at which tones of different frequencies appear to be equally loud as a standard tone -lowest pt. on the curve represents BEST sensitivity -tones in the 1000-5000 Hz range of freq. sound LOUDER than tones of = level not in the range

minimum audible angle

-smallest amount of spatial separation of 2 sequentially presented acoustic events that can just be detected -most sensitive to horizontal position changes when sound is at 0 azimuth -most senstive to vertical position changes when sound is at 90 azimuth

place and frequency theory

-Detection of sound pitches in the midrange and HIGH end is be supported by PLACE theory -Detection of sound pitches in the midrange and LOW end is supported by FREQUENCY theory -midrange sounds-both mechanisms used=better discrimination

sound discrimination

-Determine difference threshold over range of frequencies (curved lines) and volumes (axis) -Weber fractions (JNDs) are smaller for midrange frequencies ^small fraction=good discrimination -Greater sound discrimination with both ears (binaural) ^better depth discrimination w/ two eyes

Hughe's law

-From 1-200 ms sound energy is summed (if close enough in frequency) -High pressure over short time or lower pressure over longer time -In vision: Bunsen-Roscoe law (bright stimulus short duration or weaker stimulus over longer duration) *damaging ear

loudness of sounds

-Subjective determination measured in sones (brightness for vision) ^the more intense, the louder the sound -Most strongly correlated with sound pressure (amplitude) -Not all pitches are perceived as equally loud- midrange is perceived as louder when all else is equal

volley principle (frequency theory)

-addresses the issue in frequency theory -neurons fire in concert to denote frequencies greater than 1000 Hz -single ganglion wont exceed 1000 times per second but if they're all firing and hitting at different times it comes out to much faster

vision and audition

1-vision physical-3 cones psychological-opponent 2-audition physical-basilar membrane psychological-volley -we use the biological characteristics of the sensory organs and processing it further by the nervous system ^certain things get enhanced (vision ex-edges)

Minimum Audible Pressure

Sound coming from headphones

Minimum Audible Field

Sound coming from open space -thresholds are better due to reverberations (reflections of the room) and action of pinna -humans have max sensitivity at 2000-4000 Hz

equal pitch contour

have subjects adjust the frequency or pressure level to match the pitch of a standard tone -results --HIGH pitch (>2kHz) will be perceived to be getting HIGHER if loudness is increased --LOW pitch (<2kHz) will be perceived to be going LOWER with increased loudness -"Steven's rule" -2000 Hz perceived as the same freq. whether the sound is faint or loud

interear difference cues

indicated by azimuth (angle from the listener)