Physical Properties Of Sound

Question 1

Name 3 physical properties of sound:

Answer 1

Frequency

Intensity

Time

Question 2

Name 3 ways humans perceive sound:

Answer 2

Loudness

Localization

Pitch

Question 3

In order to create sound, what does the source need to be able to do?

Answer 3

Vibrate

Question 4

In order for a source of sound to be able to vibrate, it needs which 2 properties?

Answer 4

Mass

Elasticity

Question 5

Aside from the source, what else plays a role in sound production?

Answer 5

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

Question 6

What is mass?

What does it apply to?

Answer 6

It’s the amount of matter present

It applies to gasses, liquids and solids

Question 7

Elasticity - what’s the purpose of it?

Answer 7

It’s a property that enables RECOVERY from distortions in shape or volume

Question 8

Vibrations and the tuning fork:

Answer 8

Strike a tuning fork; vibration occurs

Tines DISPLACED from equilibrium

Amplitude of the displacement is proportional to the force applied

Question 9

How does vibration occur?

2 important things:

Answer 9

Due to the interaction of the 2 opposing forces:

Inertia
Elasticity

Question 10

What is meant by compression and rarefaction?

Answer 10

It’s the movement of air mass:

Compression:
crowding / increased density

Rarefaction:
thinning / decreased density

Question 11

Displacement of air medium and wave motion:

How is sound characterized?

What physical qualities do we need to consider?

Answer 11

Characterized by propagation of density hanged through elastic medium

Need to consider physical qualities:
Mass, density, force, pressure, displacement

Question 12

Sound and Transfer of energy:

Answer 12

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)

Question 13

Frictional resistance

Answer 13

Oppositional to energy transfer in the form of frictional resistance results in: amplitude of vibration diminishing over time (dampening)

Question 14

Free vs forced vibration

Free vibration:

Answer 14

NO additional energy applied the system

• air mass offers resistance
• kinetic energy transformed -> thermal energy
• dampened pattern of vibration

Question 15

Free vs forced vibration

Forced vibration:

Answer 15

• additional energy applied to the system
• system forced to vibrate by some external object
• reduces frictional resistance effects

Question 16

Resonance

Answer 16

Property of system oscillating at a particular frequency with minimum dissipation of energy

Question 17

Characteristics of pendular motion (sound transmission)

Name 2:

Answer 17

1. Amplitude of displacement
2. Frequency
   - rate of vibratory motion
   - # of cycles per second
   - unit of measure (Hz)

Question 18

What defines 1 cycle?

Answer 18

1Hz = 1 CPS

• movement from equilibrium to Maximum displacement in the opposite direction then back to equilibrium

Question 19

3 characteristics of pendular motion:

Answer 19

1. Frequency
2. Amplitude
3. Period (time required to complete 1 cycle)

Question 20

Frequency of vibratory motion:

Answer 20

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

Question 21

Speed of sound/wave propagation is governed by:

Answer 21

Properties of the medium

Air = 331 m/s
Water = 1,433 m/s
Steel = 4,704 m/s

Question 22

Transfer of energy:

Answer 22

• 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

Question 23

Simple harmonic motion:

Wave shapes x 3:

Answer 23

Impulsive
Oscillatory
Sinusoidal

Question 24

Impulsive wave:

Answer 24

Single burst of 1 or several pulses (ex. Balloon pop)

Question 25

Oscillatory wave:

Answer 25

Always have definite repeating shape.

Can be complex but ALWAYS repeated

Question 26

Sinusoidal waves

Answer 26

Simple
Repeating shape
“PURE TONE”

Question 27

Sine waves continued:

Answer 27

Sine = displacement over time

Called the “time domain waveform” or “waveform”

Question 28

5 dimensions of a sine wave:

Answer 28

Frequency
Period
Amplitude
Phase
Wavelength

Question 29

Dimensions of sine wave:

1. Frequency

Answer 29

#of cycles/second
Cycle = 1 complete transition of sinusoidal function

F = 1000 % T
Unit of measurement = Hz

Question 30

Dimensions of sine wave:

Pitch:

Answer 30

Subjective - impression of frequency

3000Hz = high pitched
250Hz = low pitched

Question 31

Dimensions of sine wave:

2. Period (T)

Answer 31

Time required to complete 1 cycle

T = 1000 % F

Question 32

Dimensions of a sine wave:

3. Amplitude (name 4):

Answer 32

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)

Question 33

Dimensions of a since wave:

4. Phase:

Answer 33

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

Question 34

Dimensions of sine wave:

5. Wavelength:

Answer 34

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

Question 35

Promotional relations:

Answer 35

• wavelength is proportionally related to speed
• wavelength is inversely proportional to frequency, which means as wavelength decreases, frequency increases because wavelength = 1/f