Waves and Sounds Flashcards
What is a sinusoidal waves?
the individual particles oscillate back and forth with a displacement that follows a sinusoidal pattern; sin wave
What are transverse waves?
waves in which the direction of particle oscillation in perpendicular to the propagation; imagine a wave in a stadium, people standing up and down but not moving sideways
What are examples of transverse waves?
electromagnetic waves, visible light, microwaves, x rays
What are longitudinal waves?
waves in which the particles of the wave oscillate parallel to the direction of propagation; in the direction of energy transfer
What are examples of longitudinal waves?
sound waves
What is a crest on a sound wave?
the top point or maximum
What is a wavelength?
(lambda) the distance from one crest to another
What is frequency?
(f) number of wavelengths passing a fixed points per second
What is the units for frequency?
Hz/cycles per second (cps)
What is the propagation speed equation?
v = frequency * wavelength
What is a period?
(T) - the number of seconds per wavelength cycles
What is the equation for angular frequency?
w = 2*pi*f = 2*pi/T w = angular frequency f = frequency T = period
What is the equilibrium point?
a central point about which waves oscillate
What is amplitude?
(A) the maximum magnitude of displacement of the wave - so length from equilibrium point to either crest or trough
What is phase differences?
a way to describe two waves relative to each other - in phase is when the respective troughs and crests decline; out of crest is the opposite
Principle of Superposition
when waves interact with each other, the displacement of the resultant wave at any point is the sum of the displacements of the two interacting waves
What is constructive interference?
the waves are perfectly in phase, the displacements always add together and the amplitude of the resultant is equal to the sum of the amplitudes of the two waves
What is destructive interference?
when the waves are perfectly out of phase, the displacements always counteract each other and the amplitude of the resultant wave is the difference between the amplitudes of the interacting waves
What are nodes?
points on the wave that remain at rest
What are antinodes?
points midway between the nodes fluctuate with maximum amplitude
What is timbre?
quality of sound; determined by the natural frequency of the object
What is sound?
a longitudinal wave transmitted by the oscillation of particles in a deformable medium
What is the equation for speed of sound?
v = sqrt(B/p) B = medium's resistance to compression p = density of the medium
What is pitch?
our perception of the frequency of sound; lower frequency = lower pitch
What are infrasonic waves?
sound waves with frequencies below 20 Hz
What are ultrasonic waves?
sound waves with frequencies above 20,000 Hz
What is the Doppler effect?
describes the difference between the actual frequency of a sound and its perceived frequency when the source of the sound and the sounds detector are moving relative to one another
What is the equation for the Doppler effect?
f' = f[(v +- vD)/(v-+ vS)] f' = perceived frequency f = actual emitted frequency v = speed of sound in the medium vD = speed of the detector vS = speed of source Top sign when detector is moving towards the object Bottom sign when moving away
What is echolocation?
emitting the sound serves as both the source and detector of the sound; the time it takes for the sound to return and the change in frequency can be used to determine positions of objects
What is a shock wave?
a moving object travels at a high speed that allows wave fronts to build upon each another in front of the object, increasing amplitude and thus compression/pressure
What is a sonic boom?
the passing of the shock wave which goes from high pressure to very low pressure
What is loudness/volume?
the way we perceive its intensity
What is the equation for intensity?
I = P/A I = intensity P = power A = area
What are the units for intensity?
watts per square meter (W/m^2)
What is the equation for sound level?
B = 10log(I/I0) B = sound wave I = intensity of the sound wave I0 = threshold of hearing (1x10-12 W/m^2)
What is the equation for change in sound level?
Bfinal = Binitial + 10 log (Ifinal/Iinitial)
What is the equation for wavelength?
lambda = 2L/n L = length of the strength n = number of nodes (harmonic)
What is the equation for frequency?
f = velocity of wave speed/lambda
