PSYC56H3 Lecture Notes - Lecture 3: Intermolecular Force, The Nerves, Middle Ear
PSYC56 LEC 3 Jan 23rd, 2018
Anatomy of the Ear
- The ear forms the path along which incoming music signals travel to reach the brain
- This is called auditory transduction
1. Acoustic sound mechanical electric to the brain
- Sound Ear Auditory Nerve Brain
- Note: the textbook is simply supplementary information to the next few lectures. If it wasn’t
covered in lecture, you’re not responsible to know it for the exam
Sound
- Sound is a mechanical disturbance of a medium
1. Medium is anything that create sounds
2. The spring & golf ball example, cause a disturbance of the medium then it pushes and
revert back that would produce sound
Speed of Sound
- The speed of the disturbance depends on:
1. The density of the medium
▪ Heavier molecules take longer to start and stop moving
2. Strength of the intermolecular forces (i.e., Young’s modulus – only apply to solid)
▪ Stronger forces will push faster and cause acceleration
- To calculate the speed of sound:
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Speed of Sound Through Air
- Generally, sound and music travels through air. However, Young’s modulus actually only applies
to solids, so you’d need to calculate adiabatic bulk modulus of air
- Will always reference it to air
Transverse wave
- Transverse waves: when molecules are moved side to side, causing a lateral disturbance to be
propagated
- Called transverse waves because the displacements are transverse to the direction of propagation
- Found in the vibrations of some instruments, such as strings or drums
1. Goes up and down sound get propagated – side way
2. Further away more energy lost, the weaker the sound is
3. Strength of string
- Formula for velocity:
Longitudinal Waves
- Longitudinal waves fluctuate in the same direction as the wave is traveling
Transverse Waves
- Transverse waves fluctuate at a right angle to the direction that the wave is travelling
find more resources at oneclass.com
find more resources at oneclass.com
Sine Waves
- So far, we’ve only discussed the propagation of a single disturbance. There are also sounds that
are periodic (reoccurring). That is, their compressions and retractions are periodic.
- This is the basis of musical pitch
- Pure tone is made up of one sine wave, not have natural source, can’t bind auditory to visual
information – a pure tone would be sound of beep (heart rate) in hospital
1. Natural sound is easier to hear than pure tone
Sine Waves
- Have three parameters:
1. Amplitude: maximum displacement of molecules from one extreme to resting position
▪ Higher amplitude = louder the sound
▪ Envelop is the Shape of amplitude
▪ Plugging – sharper sound but decay quickly
▪ Bowing – more gradual
2. Periodic vibration: wave repeated itself – whole wave to complete (3 cycle)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
The ear forms the path along which incoming music signals travel to reach the brain. This is called auditory transduction: acoustic sound mechanical electric to the brain. Sound ear auditory nerve brain. Note: the textbook is simply supplementary information to the next few lectures. If it wasn"t covered in lecture, you"re not responsible to know it for the exam. Sound is a mechanical disturbance of a medium: medium is anything that create sounds, the spring & golf ball example, cause a disturbance of the medium then it pushes and revert back that would produce sound. Generally, sound and music travels through air. However, young"s modulus actually only applies to solids, so you"d need to calculate adiabatic bulk modulus of air. Transverse waves: when molecules are moved side to side, causing a lateral disturbance to be propagated. Called transverse waves because the displacements are transverse to the direction of propagation.
