ec review 2 Flashcards
how does sound travel
source, path, receiver
what is sound
frequency, pitch, wavelength
amplitude, volume, loudness
1000 Hz = 1 ft
human range of hearing
20 Hz - 20,000 Hz
wavelength
distance sound travels in 1 second
frequency
the number of times a sound source vibrates per second; units are Hz, (or cycles per second or cps)
pitch
musical term for frequency; a high-frequency sound has a high pitch
how does age affect hearing
older people cannot hear as high frequencies as younger people
how does echolocation work
time delays, doppler shifts, frequency information
what is sound (bullet points)
- form of energy that travels in waves
- audible signal
- vibrations that travel through a medium and can be heard when they reach an ear
- mechanical wave
- oscillation of pressure that is transmitted through a solid, liquid, or gas within the range of hearing
what is vibration
- sound is heard, vibration is felt
- typically less than 20 Hz
diffraction
- high frequency sound = small diffraction
- mid frequency sound = medium diffraction
- low frequency sound = large diffraction
sound masking
- white noise
- pink noise
- vegetation
sound intensity
measure of the sound energy passing a unit area in a unit time
(measured in watts per meters squared)
loudness
subjective human perception of sound amplitude; based on strength of the sensation received by the eardrum and sent to the brain
loudness is dependent on
- distance from the source (inverse square law)
- amplitude and frequency of the vibration (source)
- density of the medium (path)
- biology of the individual (receiver)
- presence of masking
sound power measure
watt (w)
sound pressure measure
Pa (pascal)
sound intensity measure
w/cm^2
sound power
- output
- characteristic of the source
- measured in watts of acoustic power
- jet engine: 100,000w
- orchestra: 10w
- speech: 0.00001w
sound pressure
- effect of a sound at a particular location
- ambient air pressure deviation (pascals)
- near jet engine: 200 Pa
- loud nightclub: 2 Pa
- speech: 0.02 Pa
loudness: inverse square law
I = P/A
distance from the source
double/half of source power
+/- 3 dB
double/half distance from source
+/- 6 dB
density of the medium (path)
- denser the medium, the more intense the wave
- faster the wave travels, the more quickly it transmits energy
- sound intensity is less measure of amount of energy, more of the rate energy transfer
noise
unwanted sound
hearing
perception of sound
sound reflectance
hard surfaces
sound transmittance & absorptance
soft surfaces