nature of sound

sound

invisible energy that evokes the sensation of hearing

sound in acoustics

a disturbance of an elastic medium that causes an auditory sensation

three things needed for a sound to occur

vibrating object, elastic medium, and a force

speech example

vocal folds = vibrating object, air = medium, air from the lungs = force

two things that are needed for a sound to be heard

a listener and sound transmission

two physical properties a medium must have

mass and elasticity

how does energy travel through a medium

motion is passed from one molecule to the next

wave that best describes sound travel

longitudinal wave

how do particles move in a longitudinal wave

parallel to the direction of the sound source

compression

high density of air molecules (peaks)

rarefaction

air molecules spread apart (trough)

how do particles move in a transverse wave

perpendicular to the direction of the sound source

what wave motion best describes sound travel

longitudinal

propagation velocity

speed at which sound travels

what determines the speed of sound

properties of the medium, including density and elasticity

wavelength

the distance between 2 identical points on adjacent cycles

what happens to period when frequency increases?

period decreases

what happens to wavelength when frequency increases?

wavelength decreases

what happens to period when frequency decreases

period increases

what happens to wavelength when frequency decreases

wavelength increases

what does sound pressure depend on

the energy of the sound source

how does sound pressure change with distance

it decreases as distance increases

taxonomy of sound

classifying sounds into smaller groups

four classifications of sound

audibility, complexity, behavior, duration

audibility

can the sound be heard

complexity

simple or complex

behavior

deterministic or stochastic

duration

impulse or continuous

simple sound

one singular sound with one pure frequency

complex

sound containing multiple frequency components

deterministic

a periodic sound that is predictable and repeatable

stochastic sound

an aperiodic sound that is unpredictable and nonrepeatable

periodic

a pattern that repeats predictably over time

aperiodic

A pattern that does not repeat predictably

Impulse

Short duration and very loud

Continuous sound

Stays in the environment for a longer duration