Physical Properties Of Sound Flashcards
Name 3 physical properties of sound:
Frequency
Intensity
Time
Name 3 ways humans perceive sound:
Loudness
Localization
Pitch
In order to create sound, what does the source need to be able to do?
Vibrate
In order for a source of sound to be able to vibrate, it needs which 2 properties?
Mass
Elasticity
Aside from the source, what else plays a role in sound production?
To transmit sound, a MEDIUM must be present and capable of being set into vibration.
Like the source, a medium must have the same 2 properties as the source: mass & elasticity
What is mass?
What does it apply to?
It’s the amount of matter present
It applies to gasses, liquids and solids
Elasticity - what’s the purpose of it?
It’s a property that enables RECOVERY from distortions in shape or volume
Vibrations and the tuning fork:
Strike a tuning fork; vibration occurs
Tines DISPLACED from equilibrium
Amplitude of the displacement is proportional to the force applied
How does vibration occur?
2 important things:
Due to the interaction of the 2 opposing forces:
Inertia
Elasticity
What is meant by compression and rarefaction?
It’s the movement of air mass:
Compression:
crowding / increased density
Rarefaction:
thinning / decreased density
Displacement of air medium and wave motion:
How is sound characterized?
What physical qualities do we need to consider?
Characterized by propagation of density hanged through elastic medium
Need to consider physical qualities:
Mass, density, force, pressure, displacement
Sound and Transfer of energy:
Sound = “transfer of energy through an elastic medium”
- air mass offers resistance to energy transfer
- kinetic energy (energy in motion) is transformed to thermal energy (heat)
Frictional resistance
Oppositional to energy transfer in the form of frictional resistance results in: amplitude of vibration diminishing over time (dampening)
Free vs forced vibration
Free vibration:
NO additional energy applied the system
- air mass offers resistance
- kinetic energy transformed -> thermal energy
- dampened pattern of vibration
Free vs forced vibration
Forced vibration:
- additional energy applied to the system
- system forced to vibrate by some external object
- reduces frictional resistance effects
Resonance
Property of system oscillating at a particular frequency with minimum dissipation of energy
Characteristics of pendular motion (sound transmission)
Name 2:
- Amplitude of displacement
- Frequency
- rate of vibratory motion
- # of cycles per second
- unit of measure (Hz)
What defines 1 cycle?
1Hz = 1 CPS
- movement from equilibrium to Maximum displacement in the opposite direction then back to equilibrium
3 characteristics of pendular motion:
- Frequency
- Amplitude
- Period (time required to complete 1 cycle)
Frequency of vibratory motion:
The frequency of vibration of the source is determined by characteristics of the source
Tuning fork: density of metal & length of bar
String/wire: length, mass, tension
Air: frequency of vibration of air participles is the same as the frequency of the source
Speed of sound/wave propagation is governed by:
Properties of the medium
Air = 331 m/s Water = 1,433 m/s Steel = 4,704 m/s
Transfer of energy:
- sound is characterized as proposition of density changes through elastic medium
Sound is defined as transfer of energy through an elastic medium
Energy is transferred in the direction the wave is propagated
Air mass offers resistance and kinetic energy transforms into thermal energy
Simple harmonic motion:
Wave shapes x 3:
Impulsive
Oscillatory
Sinusoidal
Impulsive wave:
Single burst of 1 or several pulses (ex. Balloon pop)
Oscillatory wave:
Always have definite repeating shape.
Can be complex but ALWAYS repeated
Sinusoidal waves
Simple
Repeating shape
“PURE TONE”
Sine waves continued:
Sine = displacement over time
Called the “time domain waveform” or “waveform”
5 dimensions of a sine wave:
Frequency Period Amplitude Phase Wavelength
Dimensions of sine wave:
- Frequency
#of cycles/second Cycle = 1 complete transition of sinusoidal function
F = 1000 % T
Unit of measurement = Hz
Dimensions of sine wave:
Pitch:
Subjective - impression of frequency
3000Hz = high pitched 250Hz = low pitched
Dimensions of sine wave:
- Period (T)
Time required to complete 1 cycle
T = 1000 % F
Dimensions of a sine wave:
- Amplitude (name 4):
Instantaneous amplitude (random point on the graph)
Maximum amplitude (the point of greatest amplitude on the graph)
Peak to peak amplitude (the amplitude between 2 instantaneous peaks)
Root mean square amplitude (RMS)
Dimensions of a since wave:
- Phase:
Displacement in degrees of 4 reference points A, B, C, D
Defines the angle in degrees at the moment the rotation begins
0-90-180-270-360/0
Dimensions of sine wave:
- Wavelength:
Wavelength relates to frequency and speed of sound (the distance travelled during 1 period)
Wavelength = S (340) % frequency
High frequency = short wavelength
Low frequency = long wavelength
Promotional relations:
- wavelength is proportionally related to speed
- wavelength is inversely proportional to frequency, which means as wavelength decreases, frequency increases because wavelength = 1/f
