Properties of Sound

Frequency

number of cycles within a given time period (related to pitch perception)

Amplitude

difference in pressure b/w high and low peaks of wave (related to loudness perception)

Timbre

- large category that affects your perception of sound

- everything except for loudness, pitch, and duration

- related to harmonics, attack, and decay of a tone

Attack of tones

buildup of sound at the beginning of a tone eg. playing a string instrument and a guitar cord is played, it will sound like one thing

Decay of tones

decrease in sound at the end of tone
can be manipulated either through tone that dies out or muting a chord with your hands on guitar

Periodic tones

- A tone in which the waveform repeats
- includes pure and some complex tones

Periodic complex tones

consist of a number of pure tones called harmonics

Fundamental frequency/First Harmonic

- the lowest and most basic frequency of a sound wave

- determines the primary pitch of a musical note, and additional harmonics contribute to the overall timbre

Higher Harmonics

Additional harmonics are multiples of the fundamental frequency

Frequency spectras

plot the harmonics of a complex sound

First harmonic

200 Hz

Second harmonic

400 Hz

Third harmonic

600 Hz

Fourth harmonic

800 Hz

Pure tones

sounds that consist exclusively of a single frequency played at a constant intensity

Chord

consists of three or more individual notes eg. C major

How do we perceive chords?

even though chords consist of distinct notes we perceive them as a single "object" due to secondary auditory cortex processing

Overtones

additional tones present in a note or chord (stacking higher level frequencies on top)

Major vs Minor chord

- difference between the two is one note (eg. middle note is a single half step change)
- can affect emotional response
- minor chord sounds "sad" compared to major chord

Effect of changing the temporal structure of a note

dramatic change in both the neural response and perpetual experience they generate

Power spectra for piano

piano note played backwards or forwards contains the same basic info, yet playing a recording of a piano note backwards can make it sound > like an organ

Visualization of single notes produced by a trumpet (left) and clarinet (right)

- illus­trating their complex temporal structure

- Although the trumpet spectrum changes more dynamically than the clarinet, each partial is in constant flux

- The goal of these 3D figures is to illustrate the dy­namic nature of the harmonic structure of musical tones

What implications does temporal complexity have for the choice of stimuli used in experiential work?

choice of stimuli can help you narrow down external validity and focus on one single variable (eg. pure tones)

Schutz and Vaisberg systematic review

- conducted systematic review (qualitative approach)

- n = 212 studies

- purpose: determining the amount of amplitude variation found in the temporal structures of auditory stimuli

3 classifications of stimuli in Systematic review study

1. flat (sounds lacking temporal variation) = least realistic

2. percussive (sounds consisting of decaying notes) = lack overtones/harmonics

3. other (sounds produced by sustained instruments, eg. human voice, French horn) = most realistic stimuli

Systematic review implications for ecological validity

35% of studies reported no information about the temporal structure of their stimuli

therefore, limitations of external validity

Multidimensional scaling (MDS)

ask people to self-report their impressions of how similar or different the sounds of instruments are and then calculate the perceptual distance

Psychological scale of 72 instruments

- asked how dark or bright an instrument sounds (eg. major = bright, minor = dark)

- very subjective

- plot these points (eg. tuba and base sounds relatively dark compared to flute and clarinet)

- dotted value lines = mean value

3D Timbre space for Chinese Instruments

- graph is more complicated:

y-axis: full to mellow

x-axis: bright to vigorous

z-axis: hoarse to consonant

- subsuming different cultural categories

How is the primary auditory cortex involved in auditory perception

transforms physical properties (eg. frequency) into auditory percepts like tone height and chroma

Tone height

- perceived in anterior PAC

- the increase in pitch that occurs as frequency is increased

Tone Chroma

- perceived in posterior PAC

- the perception of the distinctiveness of a pitch apart from its octave

Pitch perception is not the same as fundamental perception

auditory illusion

Effect of the missing fundamental

phenomenon where the brain perceives the fundamental frequency of a sound even when it is not physically present in the sound wave

Bilateral lesions of the PAC

results in no change in thresholds for normal detection of sounds, yet an increase in thresholds for judging whether two sounds have the same pitch, and detecting the direction of change in a pitch

Residue pitch

the integration of a fundamental frequency and harmonics into a coherent whole

When listening to music we can process regularities in two different ways?

1. based on regularities inherent to the acoustic properties of sounds (not reliant on previous experience and occurs during direct sensory perception)

2. based on regularities that have been learned over extended periods of time (requires musical background or knowledge)

Echoic memory (sensory memory)

takes auditory stimuli and holds it for only a couple of seconds

storage of physical features of sounds just heard in the environment and can be used as a basis of comparison to evaluate incoming sounds

Local Dependency

statistical patterns or regularities that exist in the sequence of sounds, describing the underlying relationships between adjacent musical elements

Statistical Mismatch Negativity (sMMN)

specifically involves the statistical properties of stimuli and how the brain processes unexpected deviations from statistical regularities

Other forms of the MMN

based entirely on comparisons to what is in the sensory memory (diff. neurocognitive systems can be involved in processing diff kinds of local dependencies)

Non-local dependency

similar to local dependencies but relate to what is happening over a long period of time

relies more on LTM

(eg. instead of starting/ending with the same chord you end with a different chord which violates the expectations for a non-local dependency)

What happens during a violation of nonlocal depencies?

produces an ERAN ERP component (early right-anterior negativity, think voltage spike in response to a stimulus)

Latency

refers to when the ERP emerges (the left-right dimension: timing)

Amplitude

refers to the changes in the size/magnitude of electrical activity associated with the ERP (up-down dimension: size)

ERAN

- early right anterior negativity
- closely associated with nonlocal dependencies
- find them in relation to violation of expectations

Classical musicians vs. Jazz musicisans

when you get an unexpected note or tone, the classical musicians seem to get tripped up

Jazz musicians are less phased by unpredictability (they can adapt better)