Characteristics of Sound Flashcards
acoustics of sound
physical attributes of sound
psychoacoustics of sound
what we perceive as sound, perceptual attributes
frequency (Hz)
number of cycles of vibration per second
higher frequency, higher pitch
period (t, sec)
how long air molecules vibrate-the time required for each vibration cycle to occur
amplitude/intensity
how big are pressure changes
wavelength
how far waves travel
pitch
how high/low on musical scale
loudness
volume
quality
tone of sound-noise vs tone
waveform
graph that shows time on horizontal axis and amplitude on vertical, used to show pressure changes over time
what is the human range of hearing?
20 Hz- 20,000 Hz, but we hear best at 1,000 Hz- 4,000 HZ
Subsonic
below human hearing range
supersonic
above human hearing range
describe the relationship between frequency and period
there is a reciprocal relationship between frequency and period
if t=.05 sec
then F= 20 Hz
periodic waves
every cycle lasts the same amount of time, can be assigned a pitch on a musical scale
aperiodic waves
cycles last different amounts of time, cannot be assigned a pitch
ex) fricatives and stops, white noise, noise, voiceless sounds
velocity of sound
how fast sound travels in a specific direction
what is the speed of sound in air?
34,000 cm/sec or 700 mph
velocity increases when the temperature is…
warmer
velocity increases in which materials…
water and dense materials
what is wavelength?
the distance covered by one complete cycle of pressure change (measured in meters/centimeters)
How are frequency, period, and wavelength related?
higher frequency> smaller period> shorter wavelength
what is an incident wave?
the wave generated when an object vibrates
depending on the boundary of the wave, it may be..
transmitted, absorbed, or reflected
surfaces that cause reflection
hard, smooth, regular surfaces
for example, an echo!
surfaces that cause absorption…
soft, irregular, porrous
this will damp sound
interference
a way sound behaves when sounds combine with eachother
constructive interference
area of compression and rarefaction combine in a way that results in INCREASED amplitude
destructive interference
areas of compression and rarefaction that combine in a way that results in DECREASED amplitude
pure tones are also known as
sinusoids
what are pure tones?
sounds with a SINGLE frequency, the source and molecules vibrate in simple harmonic motion, sound perceived is musical but thin
complex sounds have how many frequencies?
2 or more
characteristics of complex sounds
can be periodic or aperiodic
more common in nature
only sounds humans can make
what happens when pure tones of different frequencies combine?
a complex sound is created
1 sound with 2 frequencies
complex period sounds consist of
a fundamental frequency and harmonics
what is fundamental frequency?
lowest frequency in the series/sound
harmonics
whole number multiples of the fundamental frequency
what kind of quality does adding harmonics bring to a sound/
RICH, resonant quality
perceptual correspondent to fundamental frequency is
pitch
aperiodic complex sounds consist of..
multiple frequencies which are not systematically related
RANDOM broad range of frequencies
sounds like noise
transient aperiodic complex sounds
STOPS
are brief in duration
continuous aperiodic complex sounds
able to be prolonged in duration
“ssssss”
voiced sounds
sound made by VF vibration
gives sound tonal quality
periodic
voiceless sounds
open VFs, no vibration, no tone, just noise
aperiodic
line spectrum shows..
frequency and amplitude
acoustic energy at each harmonic frequency of the sound
continuous spectrum represents..
used to represent complex aperiodic sounds
will NOT show whether sound is continuous or transient because time isn’t on this graph
quality (acoustic reference)
refers to the relationship between the frequencies in a sound and their respective amplitudes
quality (perceptual)
refers to the tone of a sound
amplitude
amount of pressure generated
intensity
output of a source generated by amp.
grows exponentially
dB scale
measures sounds accounting for amp and intensity in relation to loudness
what kind of scale is the dB?
logarithmic and ratio scale
what does the dB scale compare?
target sound to standard reference sound (SRS)
0 dB
means the target sound has same amplitude, intensity, and loudness as SRS
amp of 0 dB
20 micropascals
intensity of 0 dB
10 ^-12 watts/m^2
threshold of hearing
quietest sound that a pair or normal human ears can detect under ideal conditions, half of the time
PSYCHOACOUSTICS
advantages of using the dB scale
condenses around 100 trillion linear intensity units into some 140 log units
dB scale is more manageable than using absolute units of amp or intensity
dB level increases
linearly
amp/intensity increase
exponentially
dB SPL
sound pressure level, refers to amplitude
dB IL
intensity level
dB HL
hearing level (used on an audiogram)
threshold of hearing changes according to…
FREQUENCY
auditory area
encompasses limits of sounds we can hear
if freq. is outside of our auditory area it must have what in order to be detected?
greater levels of amp and intensity
what is the middle range freq. of hearing?
500-4000 HZ
