properties of sound and speech acoustics

hsls 3800, slideshow 2

meaningful

the auditory system allows us to extract “_________” sounds from the environmental

importance of auditory system

allows for:

• sensing of danger

• localizing the source of a sound

• communication

• learning

• entertainment

acoustics

the science concerned with the production, control, transmission, reception, and effects of sound

• the physical properties of sound in the environment

• how sound travels through the air

• how sounds are affected by objects in the environment

psychoacoustics

study of how we perceive sound

• perception of pitch

• perception of loudness

• perception of the source of sound

vibration

sounds are produced by an object that has been set into _________

pure tones

not found in everyday world, utilized by audiologists as part of a basic hearing evaluation, also called simple vibrations

complex vibrations

combination of different PTs

sound production

vibrating sound source sets up sound waves that travel through an elastic medium (i.e., air, water, most solids)

propagation

back and forth movement of air molecules in response to vibration of an object

condensation

air molecules pushed together, region in a sound wave where the particles are pushed closer together

rarefaction

air molecules pulled apart, region in a sound wave where the particles are spread apart the most

reflection

• sound bounces off objects

• flat, convex, or concave surface

• example: basketball courts at ping, sound bouncing off a metal surface

diffraction

• sound waves bend to travel around/through an object

• sound bends around corners or spreads through openings

• example: walking through Porter Hall, some professors can be overheard even with their doors closed because of sounds travelling through openings

refraction

• sound waves bend and move up/down depending on temperature and wind

• example: aquatic center/pool, sounds travels efficiently through water

absorption

• sound is “deadened” by different materials

• sound is absorbed (not bounced) by soft materials

• example: Alden Library is created by couches, shelves, carpet, etc. to absorb sound and make the environment quiet

frequency

the number of vibrations occurring in 1 second

hertz (Hz)

frequency unit of measurement

period (T)

amount of time it takes to complete one cycle of vibration

second (s) or millisecond (ms)

period unit of measurement

T = 1/f & f = 1/T

period and frequency equations

wavelength

describes how far a pure tone travels in 1.0 cycle

higher frequency = shorter λ

lower frequency = longer λ

length (feet, meters, centimeters)

wavelength unit of measurement

wavelength equation

λ = c/f

phase

the position in the cycle a vibration begins

degrees, 0 to 360

phase unit of measurement

summation, cancelation

in-phase =

out of phase =

false

true of false: humans can hear the difference between starting phases

amplitude

describes the magnitude of sound

e.g., larger magnitude = higher ______

higher

_____ amplitude = greater amounts of condensation and rarefaction

displacement, intensity, pressure

amplitude unit of measurement

sound intensity

measure of power distributed over an area, watt/m²

sound pressure

measure of force distributed over an area, newton/m² or micropascals

decibels (dB)

unit for measuring the loudness of sounds

decibel sound pressure level (dB SPL)

• loudness of sound

• output of hearing aids

decibel hearing level (dB HL)

auditory thresholds

3

when combining decimals, the general rule is sound intensity increases by __dB when intensity is doubles

inverse square law

• the further away you are from a sound’s source, the softer it becomes

• sound is distributed over a greater area

• distance doubled, pressure decreases by ½ 

20, 20,000

• human ear is responsive to frequencies from ____ to _____ Hz

• ear is not equally sensitive across frequency range

pitch

• psychological correlate of frequency

• low frequency = low ____

• high frequency = high ____

250, 8,000

conventional auditory tests are between _____ and _______Hz

temporal integration

audibility changes with the duration of a sound, sound <200ms, level must be increased to an audible

loudness

• psychological correlate of intensity

• low intensity = soft sound

• high intensity = loud sound

localization

• ability to determine direction from which a sound is coming

• time and intensity differences