Ch. 2: Sound Flashcards
All waves carry ____ from one location to another
All waves carry energy from one location to another
Sound is a ____ wave in which particles in the medium wave move
Sound is a mechanical wave in which particles in the medium wave move
Mechanically strikes other particles (Physically touching)
The molecules in the medium ____ back and forth from a ____ position
The molecules in the medium vibrate back and forth from a fixed position
Sound cannot travel through a ____; it must travel through a ____, where molecules are alternately ____ (squeezed together) and ____ (stretched apart)
Sound cannot travel through a vacuum; it must travel through a medium, where molecules are alternately compressed (squeezed together) and rarefied (stretched apart)
Sound cannot travel through a vacuum because there are no particles
Sound travels in a ____ line
Sound travels in a straight line
Are sound waves are transverse or longitudinal waves?
Sound waves are longitudinal waves
Characteristics of sound:
- (1) ____ wave— Carry ____
- (2) ____ wave
- (3) Needs a ____ because it cannot travel through a ____
- (4) ____ and ____
- (5) Travels in a ____ line and are ____ waves
Characteristics of sound:
- (1) Energy wave— Carry energy
- (2) Mechanical wave
- (3) Needs a medium because it cannot travel through a vacuum
- (4) Compression and rarefaction
- (5) Travels in a straight line and are longitudinal waves
Acoustic propagation properties
The effect of the medium upon the sound wave
- [Acoustic— Sound]
- [Propagation— To move]
- When the sound is going inside the body, what is happening to the sound
- What is the effect of media on the sound
Biological effects
- The effects of the sound wave on the biologic tissue that it passes
Acoustic variables are used to
distinguish between sound waves and other types of waves
Three acoustic variables used to distinguish between sound waves and other types of waves:
- (1) Pressure
- (2) Density
- (3) Distance
- If one of these acoustic variables has a rhythmic oscillation, then the wave is a sound wave
- If something other than pressure, density, or distance (particle motion) rhythmically oscillates in a wave, then the wave is not a sound wave
Pressure and density ____ during compression, and ____ during rarefaction
Pressure and density increase during compression, and decrease during rarefaction
Sound waves are also known as ____ ____
Sound waves are also known as acoustic waves
What is the unit of the acoustic variable: Pressure
pascals (Pa)
What is the unit of the acoustic variable: Density
kg/cm³
What is the unit of the acoustic variable: Distance
cm, mm, ft
What is pressure?
Concentration of force in an area
Pressure formula
P = F / A; Pressure = Force/Area
What is density?
Concentration of mass in a volume
Density formula
ρ = m/V; Density= Mass/Volume
What is distance?
Measure of particle motion
After a wave is identified as a sound wave, it is important to describe the wave’s features, Acoustic Parameters are used to
accurately describe the characteristics of a sound wave
List the seven acoustic parameters
- Period
- Frequency
- Amplitude
- Power
- Intensity
- Wavelength
- Propagation speed
What are the types of waves?
- Transverse waves
- Longitudinal waves
In a transverse wave, particles move in a direction that is ____ (at right angles) to the direction that the wave propagates
In a transverse wave, particles move in a direction that is perpendicular (at right angles) to the direction that the wave propagates
Particles moves up and down
Propagation means:
To move
Acoustic means:
Sound
In a longitudinal wave, particles move in the ____ direction that the wave propagates
In a longitudinal wave, particles move in the same direction that the wave propagates
- Sound is a longitudinal wave
- Sound moves from side to side
A pair of waves are considered ____ when their peaks (maximum values) occur at the same ____ and the same location
A pair of waves are considered in-phase when their peaks (maximum values) occur at the same time and the same location
- Similarly, the troughs of the waves (minimum values) occur at the same time and place
- In-phase waves are “in step”, just like the members of a synchronized marching band
When two waves are ____, their peaks occur at different times, and so do their troughs: they are “ ____ “
When two waves are out-of-phase, their peaks occur at different times, and so do their troughs: they are “out of step”
When waves lose their individual characteristics and combine to form a single wave, this combination is called ____
When waves lose their individual characteristics and combine to form a single wave, this combination is called interference
- More than one sound beam may travel in a medium and, on occasion, multiple beams may arrive at an identical location at exactly the same time
- Both in-phase and out-of-phase wave pairs undergo interference; however, they combine differently
Interference of waves may be described in two ways, depending on the phase relationship of the pair of waves:
- (1) Constructive interference
- (2) Destructive interference
Interference of Waves with Difference Frequencies
- An interesting phenomenon occurs when waves of different frequencies interfere
- At some moment in time, the waves are in-phase and the interference is constructive, while at other moments, the waves are out-of-phase and the interference is destructive
- Therefore, when the frequencies of the waves differ, both constructive and destructive interference occur
Constructive interference
The interference of a pair of in-phase waves results in the formation of a single wave of greater amplitude than either of its components
Destructive interference
The interference of a pair of out-of-phase waves results in the formation of a single wave of lesser amplitude then at least one of its components
When out-of-phase waves are of equal amplitude, ____ ____ ____ may occur
When out-of-phase waves are of equal amplitude, complete destructive interference may occur
