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PHYS-P 105: FINAL EXAM
sound |
auditory sensation in the ear
|
auditory sensation in the ear
|
acoustics
|
sound wave
|
carries information or energy from one point to another
|
csound wave
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carries information or energy from one point to another
|
Two types of waves
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longitudinal and transverse
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longitudinal wave
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compressional wave, sound in air
|
transverse
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direction of wave is perpendicular to the propagation of the wave
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Frequency (audible) range of a sound wave
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20 Hz to 20 KHz
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What happens to polarity if a wave pulse on a string is reflected from a fixed end? a free end?
|
polarity is inverted; reflects the wave
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progressive/ traveling wave
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consists of a disturbance moving from source to surrounding place, transferring energy
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Standing Wave
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A wave pattern that results when two waves of the same frequency, wavelength, and amplitude travel in opposite directions and interfere
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superposition of a wave
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constructive/destructive, add or subtract amplitudes
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Wave Interference
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Two waves collide to create large or smaller wave
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wave propagation
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the way a wave travels
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Wave lengths and doppler effect:
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Longer wavelength: when the sound moves away from you- lower pitch
Shorter wave length- when sound moves towards you- higher pitch
|
wave reflection
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wave hits barrier and reflects back with little energy loss
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wave refraction
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wave hits barrier and reflects back with energy loss
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diffraction |
low frequency waves diffract more than high frequency waves
|
resonance |
the response of standing waves to others of the same frequency
|
partial harmonics
|
waves in sound that
are integer multiples of the fundamental frequency
are of decreasing energy as distance grows from the fundamental frequency
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Overtones/partial
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all of the tones over the fundamental frequency.
Partials: Includes fundamental frequencies, but overtones do not.
|
acoustic impedance
|
Opposition of flow of energy
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Sound pressure
|
changes in air pressure due to the passage of sound energy
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Outer Ear
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- pinna
- external auditory canal
Ear Drum
|
middle ear
|
-Oval window
-eustachian tube
-auditory ossicles
Regulates ear pressure
|
Inner ear
|
cochlea
functions in hearing and balance; filled with fluid |
place pitch theory of pitch perception:
|
freq=distance traveled on basilar membrane
|
critical bands
|
frequency regions in cochlea need to recognize a separation in the brain btw frequencies
|
a critical band for a given frequency is:
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-100 Hz below 500 Hz
-10%-20% of the frequency above 500 Hz
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Masking Sound
|
when to separate sources of sound are perceived simultaneously, obscuring each other
|
psychophysics
|
the measure of stimulus strength and sensitivity to the stimulus
|
Fourier analysis breaks up complex tones into 2 things:
|
fundamental frequency
&
harmonics
|
fourier synthesis
|
adds amplitudes of waveforms
|
pure tones with slightly different frequencies are:
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beats/rough tones
|
when two pure tones are within 15 Hz of each other we hear:
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the difference in freq. btw the two and the average pitch
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when two pure tones are greater than 15 Hz but less than the limit of freq. discrimination:
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we hear a rough tone and the average freq.
|
when two pure tones are greater than the limit of freq. discrimination:
|
we hear them as individual tones
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combination tones
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when 2 loud tones are sounded together, a 3rd tone is heard thats not actually present in the audible sound
|
Dissonance
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Uncomplimentary tones; disharmonious, builds tension
|
consonance
|
repetition of final consonant sounds
|
all western scales use the:
|
octave |
pythagorean scale
|
based on intervals of fifths
|
equal temperament
|
12 pitches per octave
|
What instruments are in the brass family?
|
trumpet, cornet, trombone, tuba, French horn, etc.
|
oscillations in a pipe
|
variations of phase and amplitude
|
which family has a mouthpiece and a bell?
|
brass |
white noise
|
all frequencies with each frequency having the same amplitude
|
phoneme |
smallest unit of speech
|
formants
|
frequency regions of phonemes where harmonics have high amplitudes
|
speech sounds can be analyzed using:
|
spectrograms |
spectrogram
|
graph of frequency (y-axis) as a function of time (x-axis)
|
Direct current
|
electrons flowing through a wire in a single direction
|
volt
|
unit of energy per unit charge
|
basic unit of current
|
Amp
|
alternating current
|
voltage that changes in a sinusoidal manner
|
effective voltage
|
the ac voltage that would have the same effect as a dc voltage
|
dynamic loudspeaker
|
has a cone and voice coil, current flows through coil which moves due to Faraday's law
|
electrostatic speaker
|
conductors on outside separated by an insulator, when voltage is applied it bends which moves air and creates sound
|
shortcoming of a speaker
|
sound from the back will interfere with sound from the front causing reduced response
|
Three basic types of enclosures
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infinite baffle, acoustic suspension, tuned port/bass reflex system
|
loudspeakers in general have limited ranges of:
|
frequency response
|
woofer |
a loudspeaker designed to produce a low-frequency sound
|
Tweeter |
A loudspeaker designed to produce high frequency sounds
|
how are electrical signals from the amplifier split up and how are they sent to the correct speaker?
|
split up by frequency and sent to the correct speaker by a crossover circuit
|
microphone |
converts sound pressure or sound velocity to a voltage
|
what are the two ways in which microphones are classified?
|
-type of transducer
-directionality
|
electromagnetic microphone
|
voltage generated by motion of conducting coil, voltage output is low and must be amplified
|
piezoelectric microphone
|
voltage generated by squeezing a crystal, has high output impedance
|
Condenser Microphone
|
high quality mic that can be very small and is generally powered by phantom power or a power supply
|
bidirectional microphone
|
most sensitive to the front and back
|
bidirectional microphone
|
most sensitive to front
|
omnidirectional microphone
|
converts sound waves into digital signals
|
digital to analog converter
|
converts digital data into voltage/electric charge
|
how many digits do binary numbers have? digital?
|
2 (0 and 1); 10
|
how many bits make a byte? a nibble?
|
8; 4
|
Lossy and lossless
|
-Lossy: can't restore file to original state (usually media)
-Lossless: can restore file to original state (usually text files)
|
what type of recording to compact disks use?
|
16 bit recording
|
Nyquist Criteria
|
Minimum sampling rate (2*max frequency)
|