Waves involve a disturbance passed along from point to point; in the case of sound waves, it involves a change in _____________ and density of the air.
pressure
At what speed do sound waves travel (at around room temperature)?
344 m/s
Sound waves require some type of medium, such as gas, liquid, or solid, for propagation to take place. T or F
True
Briefly define "wavelength.
A wavelength is the equal spacing of the crests or troughs of a wave
If you know the frequency and wavelength of a wave, how would you calculate the velocity of the wave?
The velocity of the wave is equal to the frequency multiplied by the wavelength
Only transverse waves propagate through liquids or gases. T or F
False
The speed of a wave in a wire or string depends on the ________ and the mass per unit of length.
tension
When an incident pulse reaches the fixed end of a rope, the rope will stop moving. T or F
False
When an incident pulse reaches the free end of a rope (like the end of a whip), the pulse will travel back but will be right side up (not inverted). t or f
True
Describe the principal of linear superposition.
If two waves are traveling in opposite directions, they are able to pass right through each other and emerge with their original identities. If any point in time their displacements or pressures add together
__________ interference is the addition of waves or pulses when the displacements (or pressure changes) have the same "sense" (positive vs. negative).
constructive
_____________ interference is the subtraction of waves or pulses when the displacements (or pressure changes) have the opposite "sense" (positive vs. negative).
destructive
A _________ wave is created when two waves with the same frequency and amplitude are traveling in opposite directions in a medium, and the result is a wave that does not appear to move in either direction.
standing
In the case of two identical (frequency and amplitude) waves traveling in opposite directions on a rope or strings, the points of zero displacement are called ________.
nodes
In the situation in the previous question, points of maximum displacement are called _________.
antinodes
The points of maximum displacement in the previous question are a full wavelength apart. t or f
false
Standing waves can result when waves are reflected back to meet the oncoming waves. t or f
true
If two incident waves do NOT have the same amplitude, resulting standing waves will have nodes that are points of minimum, but not zero, displacement. t or f
true
If a positive sound pressure pulse travels down a pipe toward one closed end, the pressure at the end will build up to twice the pressure of the pulse, and the pulse reflects back as a positive pulse. t or f
true
An open end of a tube is analogous to a fixed end of a rope, because a sound pulse will reflect back with the opposite sense (negative if the initial pulse was positive in pressure) t or f
true
The speed of sound ___________ as temperature increases.
increases
the doppler effect
An observed change in the frequency of a wave when the source or observer is moving
If a sound source and an observer are moving towards each other, then the perceived frequency will be _____________ than the frequency of the original sound source.
greater
Reflection of waves from a curved barrier can lead to the _________ of energy at a point, for example in "whispering galleries.
focusing
___________ is the abrupt change in direction of sound waves when they encounter a barrier.
reflection
___________ is the bending of sound waves when the rate of speed of a sound wave changes because of changes in the medium.
refraction
_______________ is the ability of a sound wave to move around objects or to spread when they pass beyond a narrow opening.
diffraction
The size of an object or opening determines the amount of diffraction, and the amount of diffraction is independent of the wavelength (and frequency) of the sound.
false
Standing waves exist in a room due to _________ between waves reflected from the ceiling, walls, and other surfaces.
interference
Interference of waves from two identical sources can cause patterns of minima and maxima.
true
Briefly define "resonance.
Resonance: If a small push is supplied to a vibrating system at the right time each cycle, energy added and amplitude increased.
A graph of amplitude as a function of frequency for a resonant vibrating system has a width measured at an amplitude of 71% of the maximum amplitude that is often called ________________.
linewidth
A vibrating system with a high Q value will have a sharper resonance than a system with a low Q value.
true
A vibrating system that rapidly loses energy will have a higher Q than a system that loses its energy slowly.
false
Phase may be thought of as the starting point of a vibration.
true
For a driven vibration, if the driver is above the frequency of resonance, the driver and the vibrating mass have the same phase.
false
If a string is fixed at both ends, then the wavelength of the fundamental will be ________ the length of the string.
twice
A(n) __________ is a mode of vibration that has a frequency that is a whole-number multiple of the fundamental frequency.
harmonic
The first harmonic is the fundamental mode.
true
Modes that have frequencies that are higher than the fundamental frequency are called ________ (though we will generally avoid this term to avoid confusion).
overtones
The second harmonic is the first overtone (assuming a harmonic spectrum).
true
The term "____________" refers to all the modes, the fundamental plus all the overtones, whether they are harmonics or not.
partials
A _____________ is like a "recipe" that specifies the relative amplitude of the partials of a vibrating system.
spectrum
In a pipe, the displacement of the air is greatest, but the air pressure is equal to atmospheric pressure, at a(n)...
open end
In a pipe, the pressure variation is maximum at a(n)...
closed end
In a pipe with two open ends, the wavelength of the first mode of vibration is twice the length of the pipe (ignoring end correction).
true
In a pipe with one closed end and one open end, the wavelength of the first mode of vibration is ___________ the length of the pipe (ignoring end correction).
4 times
In a pipe with one end open and one end closed, the resulting modes include both even and odd harmonics.
false
What is "end correction," and how much end correction is needed at each open end of a pipe?
The end correction is when the actual pipe doesn't have zero pressure change right at the end, but slightly beyond the end, so acoustically the length is slightly longer. One would need to add an additional length to the average length, equal to 0.61r, wh
Resonances produced in the vocal tract (partly due to constrictions and changes in diameter) and are called ____________.
formants
Resonances produced in the vocal tract (partly due to constrictions and changes in diameter) and are called ____________.
impedance
Where there is a constriction, a change in diameter, or a sidebranch in a tube, the impedance change at that point leads to reflection of the sound waves.
true
The main air resonance of an acoustic guitar is essentially a Helmholtz resonance.
true
Violins, guitars, and other string instruments depend almost completely on _____________ vibrations of the wood sounding box for radiation of their sound.
sympathetic