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Physics midterm 1
physics midterm study materials
69
Physics
Undergraduate 1
09/28/2010

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Term
Acoustics
Definition
science of sound
Term
Music
Definition
intentional combinations of sounds that we choose to hear for esthetic enjoyment and usually depends on an orderly pattern of sounds for its pleasing effect
Term
Speech
Definition
communicate the entire range of human ideas through word symbols rather than by conveying emotions directly
Term
Noise
Definition
all sounds, especially those that are unorganized, unpleasant, or unwanted
Term
Ultrasonics
Definition
vibrations too fast for the ear to detect, nevertheless useful for calling dogs, detecting burglars, and removing dirt from small machine parts.
Term
Infrasonics
Definition
vibrations too slow for the ear to detect, used by atmospheric physicists to study blast waves or weather systems
Term
Underwater sound
Definition
useful in detecting submerged objects, whether schools of fish or submarines, with sonar devices
Term
structural vibration
Definition
building motion caused by wind, earthquake, or trampling of feet
Term
Physiological acoustics
Definition
mechanisms of ear and nerve operation and their pathology, often involving experiments on animals
Term
Psychological acoustics
Definition
human perception of sound: judgements, comparisons, and reactions to various sounds
Term
Speech and hearing
Definition
organization of sounds for human communication; strong emphasis on therapy for correction such problems as stuttering, aphasia, and deafness
Term
Noise measurement and control
Definition
rapidly burgeoning activity in response to concerns about environmental noise, including aircraft, highway, traffic, machinery, rock concerts
Term
Architectural acoustics
Definition
designs and materials for improving homes, offices, and concert halls
Term
musical acoustics
Definition
mechanisms of sound production by musical instruments; effects of reproduction processes or room design on musical sounds; human perception of sound as music
Term
Production of sound
Definition
how sound is created
Term
propagation of sound
Definition
how it travels from one place to another
Term
perception of sound
Definition
how it affects the senses and emotions of a listener
Term
how does sound originate?
Definition
when something moves back and forth really fast
Term
Pitch
Definition
the sensation of how "high" and "low" a sound is

psychological impression of the height of a sound

high pitched sounds often called treble
low pitched sounds often called bass
Term
Loudness
Definition
the sensation of strength or weakness in sound

psychological impression of sound strength; measured in sones
Term
linear sounds
Definition
many different sounds can travel through the same space at the same time, and each will be unaffected by the others.
Term
vibration
Definition
rapid back and forth movement of a single object or of a singe small piece of some large object
Term
wave
Definition
a disturbance traveling outward in all directions from a vibration source
Term
compressions
Definition
the density and pressure of the air are greater than they would be in the absence of the sound wave
Term
Rarefactions
Definition
the density and pressure are reduced below their normal values
Term
transverse wave
Definition
vibration travels in the direction perpendicular to the length of the object as the wave passes through
Term
longitudinal wave
Definition
vibration of each little parcel of the air is aligned parallel to the direction of wave travel

sound in air
Term
crests
Definition
areas of greatest compression
Term
wavelenth
Definition
the distance from one crest to the next along the direction of travel

represented by the greek symbol lambda λ
Term
the speed of sound in dry air at room temperature
Definition
344 m/s = 344 hz (T=20 degrees C)
Term
Nondispersive medium
Definition
all sounds, whether high or low in pitch, travel through the air at the same speed

air is an example of a nondispersive medium
Term
Displacement amplitude
Definition
the distance each bit of air moves to either side of its normal position during its vibration
Term
pressure amplitude
Definition
the maximum increase of air pressure in a sound wave compression
Term
force
Definition
a push or pull of any kind, with total strength measured in newtons
Term
vectors
Definition
physical quantities having both direction and magnitude
Term
tension
Definition
total force
Term
Pressure
Definition
force per unit area, p=F/S

measure of how much force is concentrated on each part of a surface

units are N/m2 (newtons for meter squared)
Term
atmosphere
Definition
an alternative unit to measure pressure
Term
what does it mean to say that air is springy
Definition
if you try to squeeze it into a smaller volume it will push back with increased pressure

springiness of air is essential to sound wave motion-the increased pressure in each compression pushes outward in all directions on the surrounding air parcels where the pressure is lower, moving them aside so that the compressed air can reexpand.
Term
what does each musical not contain?
Definition
many individual sound vibrations
Term
frequency
Definition
repetition rate of a vibration, measured in Hz
Term
Period
Definition
length of time taken for a single complete cycle of vibration

P=1/f
Term
range of audible frequencies
Definition
about 10 octaves
approximately 20Hz to 20,000Hz
Term
velocity equation
Definition
velocity (meters/second)= f (cycles/second) X λ (meters/cycle)
Term
functional relationship
Definition
expression of how one variable is related to another
Term
equilibrium
Definition
any system configuration for which all forces are precisely balanced; when placed in this configuration, the system will remain at rest
Term
restoring force
Definition
any force whose action is always in such a direction as to return an object to an equilibrium position
Term
inertia
Definition
tendency of any moving object to continue onward with constant speed; a direct consequence of the object's mass
Term
mass
Definition
how much matter an object is made of and is measured in kilograms

responsible for the property of inertia
Term
Weight
Definition
the force with which a mass is attracted to the Earth
measured in newtons

weight=mg
Term
amplitude
Definition
maximum change in any variable during each cycle of any vibratory disturbance
Term
simple harmonic motion
Definition
sinusoidal motion such as that of a mass bouncing on the end of an ideal linear spring, or that of a natural mode
Term
Work
Definition
the transfer of energy to an object whenever a force moves it through a distance W=fd
Term
Energy
Definition
capacity for doing work.

kinetic (due to motion)
potential (due to location, distortion, or chemical state)
Term
resonance
Definition
vibration of especially large amplitude occurring when three conditions are fulfilled:
1. a system with a natural vibration mode frequency (Fn) is acted by 2. an alternating driving force with frequency (Fo) and 3. is nearly the same as Fn
Term
octave
Definition
the particular musical interval characterized by the perception that one pitch seems just like the other even though distinctly higher

a natural unit of measurement for the separation of two notes in pictch
Term
what happens if we double the length of a tube
Definition
sound waves will take twice as long to go down and back, and whatever regular oscillations may occur will have twice as long a period as before, or half the frequency
Term
echoes
Definition
most easily noticed at distances of 50 to 100 meters from a large, flat, hard surface

sound will reflect from surfaces of any shape or size. if the surface is smooth, the reflection is regular and orderly. but a rough surface causes irregular or diffuse reflection

the reflected wave is always weaker than the original, because part of the sound energy is absorbed at the reflecting surface
Term
refraction
Definition
change of direction of wave travel due to difference in its speed from one place to another, to be distinguished from diffraction, which takes place even when the wave speed is the same everywhere
Term
diffraction
Definition
characteristic behavior of all types of waves, in which they tend to spread outward in all directions after passing through an opening, or to fill in the region behind an obstacle rather than leaving a shadow
Term
sound wavelengths
Definition
rage from approximately 10-15m for the lowest audible notes down to 2cm for the highest
Term
the doppler effect
Definition
a relatively high pitched sound from the approaching source changed to a lower pitch as the source receded
Term
interference
Definition
combination of signals of the same frequency from two or more sources, which may cooperate at some points in space (constructive interference) but cancel at others (destructive interference)
Term
beats
Definition
slow rise and fall of perceived loudness when signals with slightly different frequencies are combined.

a series of accented musical events, evenly separated in time

Fb = l F1-F2 l
Term
sine wave
Definition
the simplest, smoothest waveform, one produced by simple harmonic motion.

its fourier spectrum consists entirely of the fundamental, with no higher harmonics
Term
periodic wave
Definition
a vibration that repeats precisely the same pattern over and over again, thus producing a steady tone

f=1/P
Term
Fourier Spectrum
Definition
mathematical representations of the equivalence between a complex waveform and a mixture of pure sine waves or fourier components
Term
white noise
Definition
noise whose spectrum includes equal amplitudes at all frequencies
Term
Ohm's Law
Definition
in acoustics, the statement that human perception of a sound is determined entirely by the amplitudes of its Fourier components and not by their relative phases. True only within limited circumstances. In electric circuits, a relation among current, voltage, and resistance
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