Chapter 12: Psychoacoustics Flashcards
psychophysics
perception of the physical world
the study of the relationship between the physical world and the perceptual world across all of the senses: hearing, taste, vision, smell, and touch
psychoacoustician
someone who studies human response to sound
psychoacoustics
the study of the relationship between the acoustic world and our auditory image of this world.
the study of human response to sound; the study of the relationship between the acoustic stimuli and the sensation and perception of these stimuli
sensation
the awareness of an external stimulus or some change in the body caused by an external stimulus.
psychophysical measurement
measurements of sensation.
sound/visual image are presented to a
person
response to stimuli are called judgments
the measurement of sensation caused by a physical stimulus
trained listener
a human listener who has been trained to listen to a specific stimulus and is, in general, more sensitive to specific changes in the stimulus than an untrained listener.
loudness
the property of sound that allows sounds to be ordered on a scale extending from quiet (soft) to loud; loudness depends mainly on the intensity of sound.
Loudness is affected by duration if a sound is shorter than about 200ms
judgment
a human response to a test stimulus
threshold
the point at which the intensity level of a stimulus is just large enough to cause a change in the mental response of a person affected by the stimulus.
absolute threshold
the minimum value of a stimulus that elicits a specific ration a certain percentage of the time (usually 50%)
detection threshold
sensory threshold
the lowest intensity of a stimulus that can be detected a specific percentage of the time usually 50%
recognition threshold
cognitive threshold
the lowest intensity of a stimulus at which the stimulus can be recognized a specific percentage of time, usually 50%
terminal threshold
the threshold indicating the maximum value of a stimulus that elicits a given response (e.g., the terminal threshold for auditory sensation is the maximum intensity level at which response is perceived as a sound intended of pain.
difference threshold difference limen (DL)
the smallest physical difference between two stimuli in which an observer can determine that the two stimulations are perceptually different; also known as just noticeable difference (jud)
YN (yes no) technique
a threshold testing technique in which the listener is given a number of trials with some of them containing a signal and some of them hot containing a signal and the listener is asked to respond “yes” or “no” at each trail.
N-Alternative Forced Choice (nAFC)
a technique for determining threshold in which a listener is presented with a number (n) of observation intervals, one of which contains a signal, and the listener must select the interval that contained the signal.
Weber’s Law
a general property of human perception that the smallest perceived change in stimulus intensity is proportional to the stimulus magnitude.
psychophysical methods
(3)
all of the variations of the YN and nAFC techniques originate from three classic psychophysical methods
1) Method of limits
2) Method of constant (random) stimuli
3) method of adjustment
Method of limits
a psychophysical method of threshold determination in which a stimulus is gradually increased and decreased by an examiner until the threshold has been obtained
Method of constant (random) stimuli
selected signals are presented in random order
the threshold is the 50% response level.
time consuming and generally reserved for research studies.
a psychophysical method of threshold determination in which the value of the stimulus in individual trials is determined at random.
Method of adjustment
a psychophysical method of threshold determination in which a listener manually adjusts test stimuli in a series of trails until the threshold has been determined.
Method of adjustment
a psychophysical method of threshold determination in which a listener manually adjusts test stimuli in a series of trails until the threshold has been determined.
psychophysical scale
the relationship between HUMAN REACTIONS and PHYSICAL STIMULI causing the reactions
(e.g.,) the relationship between sound intensity and sound loudness
psychophysical function
illustrates the relationship between the stimulus magnitude and the sensation magnitude.
Hearing area
auditory response area
the range of perceived intensities across frequency from the lowest intensity sound a human can perceive to the threshold of pain and from the lowest to highest frequency humans can hear.
DL for intensity
DL(I)
the smallest perceivable change in sound intensity.
varies from about .5 dB to 3.0 dB, depending on the sounds and listening environment
Phon
unit of loudness
reference point fr the Phon scale is 1000 Hz at various sound pressure levels.
equal loudness curve
connects points of equal loudness across frequency
Loudness scale
a psychophysical scale in which the loudness of sound is quantified as a function of sound intensity; an example of the loudness scale is the sone scale.
Sone scale
the most common loudness scale
one Sone is the loudness of 100 Hz tone with an intensity of 40 dB SPL
Pitch
the property of sound that allows sound to be ordered on a scale extending from low too high.
if sound frequency changes by a perceptible amount, the perception is a change in pitch.
it is also possible for a change in intensity to SOUND like a change in pitch.
Mel scale
scale relating frequency and pitch
Masking
the ability of one sound (the masker) to completely block out or to decrease the audibility of another sound (Maskee)
Simultaneous masking
when two sounds arrive together
Wegel and Lane (1924) performed a tone-on-tone masking experiment and demonstrated some principles of masking for tonal stimuli.
(NOTES 188)
Temporal masking
(2)
Forward Masking- the masker is presented slightly BEFORE the signal
Backward masking-the masker is presented slightly AFTER the signal.
Critical band phenomenon
when a pure tone is masked by a band of noise and the bandwidth of the noise is increased (keeping spectrum level constant), the masked threshold will increase until the bandwidth reaches a certain width, but will remain constant if the bandwidth is increased beyond that point.
timber
the perception associated with sound complexity.
Examples of scales of timber:
sharpness (sharp-dull)
brightness (dark-bright)
sound quality
the property of sound that allows us to scale sound along EMOTIONAL SCALES)
Examples
pleasantness
annoyance
Spatial hearing
Auditory localization
the process of judging the direction of an incoming sound. It depends on:
- binaural cues - monaural cues - head movements - familiarity with the sound source
binaural cues
Interaural Intensity differences (IID)
Interaural Time differences (ITD)
monaural cues
directional cures resulting from sound reflections and diffractions around the ridges of the pinnae and upper torso
head movements and familiarity
moving the head during continuous sounds can assist in locating a sound.
a person who is familiar with a specific sound can more easily determine there direction and distance of sound,
Binaural hearing
important for speech
2-3 dB improvement
Lateralization
Identifying the location of a sound within the head is called lateralization
when listening via earphones, the use of IID’s and ITD’s creates the illusion that the sound source is located in various locations within the head.
