The Physics of Sound and Sound Perception Sound is a word of perception used to report the aural, psychological sensation of physical vibration Vibration is any form of to-and-fro motion To perceive sound you must have: 1. energy in the system, movement 2. vibrating body 3. medium of transmission 4. receiver, someone to perceive 1 2 Sine wave - graph of simple sound Wavelength - distance from one point on the wave to the next Properties of vibrating bodies 1. elasticity 2. momentum Periodic motion - ability of motion to repeat - one full repetition is a cycle Properties of the wave 1. Period = amount of time for one cycle 2. Frequency = number of cycles repeated in one second -heard as pitch 3. Amplitude = amount of displacement of the vibrating body -heard as loudness 4. Simple harmonic motion + restoration force is equal to force of displacement = frequency is independent of amplitude 3 4 Sound must travel through a medium - properties of the medium determines speed and efficiency of transmission elasticity and density Process of transmission is propagation - alterations of compressions and rarefactions Impediments to propagation -reflection -diffusion - absorption -refraction - diffraction - interference (beating) All sound occurring naturally is complex sound Complex patterns of vibration Produces the overtone series 5 6
Whenever a system that can vibrate with a certain frequency is acted on from the outside by a periodic disturbance that has the same frequency, vibrations of large amplitude can be produced in the system Resonance frequency of a vibrating body Sound decay Sound envelop - initial transit -steady state -decay Noise 7 8 Factors in the environment that influences the ability of sound to travel from the source to the ear Reverberation Reverberant sound Reverberation time - T Factors in room acoustics 1. frequency range of instrument 2. absorption qualities of the room 3. room shape 4. objects that could interfere 5. echoes 6. noise elements 7. sound output to meet room size and configuration 9 10 Hard to define A number of ways to define music 1. What are the elements or events that make up music? 2. What are the origins of music? 3. What is the purpose or uses of music? 4. What are musical behaviors or the psychology of music? Rhythm - ordered characteristic of tonal succession - aspects of musical timing 1. duration 2. beat 3. meter 4. tempo 5. rhythmic pattern 11 12
Melody - movement of tones over time that creates a shape or contour - using intervals or the relationship between notes of a melody Harmony - vertical pitch structure - tonality or loyalty to a tone Timbre - characteristic of sound that distinguishes one tone from another when pitch and loudness are constant Musical form - overall design of composition -musical style Dynamics - five dynamic ranges possibly musically pp = very quiet p = quiet mp = medium or middle f = loud ff = very loud 13 14 Divine gift Biology 1. Fundamental processes of neural activity 2. Inherent ability programmed in the brain like speech 3. Necessary anatomical structures 4. Music as a complex biological adaptation 5. Inherent, abstract form of human expression Cultural/social phenomena Pleasure/entertainment Aesthetic response Support to basic humanity as a moral force Touching the Divine Communication Effects on activity Support of human culture Healing/ritual 15 16 is the process by which sound is transmitted from the environment to our brain is the perception of sound input assigning meaning to aural input is a process of modeling the complex patterns of relationships of sound The sensory apparatus of hearing - functions as a receiver of sound and a mechanism for changing mechanical energy of sound wave into the electrochemical energy of the brain Ear is divided into three part 1. the outer ear - pinna - ear canal or meatus - tympanic membrane - functions to gather and amplify sound waves focusing them tothe tympanic membrane 17 18
2. middle ear - ossicles or 3 bones of middle ear - functions to increase the power and decrease size of the vibration - Eustachian tube - functions to equalize air pressure - acoustic reflex - two muscles, tensor tympani and stapedius - functions to stiffen the ossicles to protect the ear 3. inner ear - vestibule, a transitional area - 3 semi-circular canals, for vestibular sense - cochlea, the transducer of energy 19 Anatomy - tube within a tube - oval window -cochlear duct - Organ of Corti - basilar membrane - tectorial membrane 20 Function - coding for pitch and loudness perception - place theory of pitch perception 21 Neurons - properties of irritability and conductivity -anatomy cell body with nucleus dendrites axon synapse pre- and post-synaptic terminals neurotransmitters myelin sheath - neural transmission action potential sodium pump chemical neurotransmitters over the synapse 22 Auditory nerve bundle - afferent and efferent pathways Impact of auditory nerve on the brain - lower brain/brain stem reticular activating formation cerebellum - Mid-brain/limbic system thalamus amygdala hippocampus hypothalamus - Upper brain/cerebrum cerebral cortex four hemispheres - Corpus Colosum Auditory pathways to the brain - two contralateral - two ipsilateral Sympathetic and Parasympathetic nervous systems 23 24
Pitch is our subjective evaluation of the frequency of simple sound or the fundamental of complex sound Basilar membrane and pitch perception - the critical band Factors and processes in pitch perception - audible hearing range - duration of sound - Place Theory of Pitch Perception - Periodicity Pitch Theory - Gestalt Theory of Perception - The Law of Common Fate Pitch Perception - difference limen - perfect or absolute pitch - combination tones 25 26 Subjective evaluation of the strength of sound Decibel scale (db) Factors influencing loudness perception -hearing mechanism - frequency Loudness discrimination Volume and density Parameter of sound that distinguishes one tone from another even when pitch and loudness is the same Factors in determining timbre - characteristics of the initial transient - variations in the components of the complex tone - it s all about overtones - resonance of the instrument formant regions -vibrato 27 28 Consonance and dissonance Intervals, scales, tuning and temperament - scale pattern of audible frequencies arranged in an ascending or descending order - interval separation of two tones - expressed as a ratio relation of the frequencies of the two notes in the interval All are derived from the Pythagorean scale of Pythagoras of Greece - Pythagorean comma - just intervals - enharmonic equivalents Modifications of Pythagorean Scale temperament - Just intonation - Meantone intonation - Equal temperament 29 30
Successive combinations of tones placed in a temporal sequence -contour - tonality Harmony - perception of simultaneously sounding tones Rhythm as stimulus in music -beat - meter -tempo - accent Rhythm as response theories - Instinctive Theories - Physiological Theories - Perceptual Motor Response Theories - Learning Theories 31 32 Tactile on the skin Body resonance Haptic Kinesthesis Proprioception Synesthesia Criteria for a skilled motor behavior - fine motor skill - serial skill - movement in a hierarchical organization - spatial organization - temporal organization - involves sensory integration - involves feedback or knowledge of results Physiological Componenets 33 34 Plucked string instrument Stretched string is capable of producing a full range of overtones Dependent on where string is plucked Physiological Response - Thalamic response - Galvanic Skin Response (GSR) -Brain waves - delta (0-4Hz) - theta (4-8Hz) - alpha (8-13 Hz) - beta (13-30 Hz) - gamma (over 30 Hz) - changes in muscle tension - universal movement patterns and emotional states - biochemical responses 35 36
Affective response to music - emotions - feelings - mood - temperament Aesthetic response Human Bio-Energy fields Dense energy - Electromagnetic energy - piezoelectric property - Bodily acoustic energy Subtle energy - non-physical yet active field Non-Hertzian Energy - quantum field - consciousness and thought 37 38