Nature of Sound, Signals, & Sine Waves Flashcards
1
Q
What is a signal?
A
- A gesture, sound, or action that conveys information about how one parameter varies with another parameter
- Carries meaning
- EX: sound wave
2
Q
What is a system?
A
-Any process that produces an output signal in response to an input signal
3
Q
What is sound?
A
- Emphasize the physical not psychological perspective
- Sound source must be able to vibrate
- Must have mass (m) and elasticity (E)
- Medium of transmission must be capable of vibration
- Vibratory motion is caused by the interaction between inertia and elasticity –> to and fro movement
- Consistent with Newton’s 3rd Law of Motion
4
Q
What is Newton’s 1st Law of Motion?
A
- Law of Inertia
- Any body in motion will stay in motion and any body at rest will stay at rest unless acted upon by another force
- Magnitude of inertia is proportional to mass
5
Q
What is Newton’s 3rd Law of Motion?
A
- Law of Restoring Forces
- With every force there is an equal and opposite reaction force
- Vibration: elasticity is the reaction to inertia
- Vibration continues without reapplication of external force and is sustained by the opposing forces
6
Q
Describe the vibratory motion of a spring.
A
- System engages in simple harmonic (sinusoidal) motion
- Spring can be compressed
- Elasticity (restoring forces) opposes deformation forces
- As the spring is compressed, greater force is required for additional compression
7
Q
What is Hooke’s Law?
A
- Magnitude of restoring force (F) is directly proportional to the magnitude of displacement (x)
- -> F = -k * x
- Stiffness is the spring constant “k”
- Compliance is the inverse of stiffness
8
Q
Describe the movement of the pendulum.
A
- Example of slow moving vibration
- Restoring force is gravity not elasticity
- Gravity is highest at peak heights (max. potential energy)
- Elasticity is highest at equilibrium (max. kinetic energy) - Period of pendulum: T = 2 * pi * sqrt(L/G)
9
Q
Describe the movement of the tuning fork.
A
- Example of movement of air mass
- Alternate regions of compressions/rarefactions
- Density increases: compression
- Density decreases: rarefaction - Medium isn’t displaced over a great distance (disturbance wave moves through elastic medium)
- Sound propagation of density changes through an elastic medium
- Sound source acting on a medium
- Place the tuning fork in the medium
- Before force, particles are equidistant from each other
- Particles move about positions of equilibrium because of m and E
10
Q
Describe types of wave motion.
A
-Classified by direction of vibration of medium re: direction of wave propagation
- Transverse Wave Motion
- Vibration is perpendicular to direction of wave propagation
- Elements move up and down (note peaks and valleys) - Longitundinal Wave Motion
- Direction of particle movement is parallel to wave movement
- Elements of move back and forth (note nodes and antinodes)
- Sound waves are longitudinal waves
11
Q
Describe the properties of the transmitting medium.
A
-Mass (m)
- Elasticity (E)
- Property that enables recovery from duration of shape/volume - Density (rho)
- Mass per unit of volume
- Decreases as you rise above sea level - Atmospheric Pressure
- 14.7 lb/in^2
- 100,000 N/m^2
- 1,000,000 Pa
12
Q
List the characteristics of sound.
A
- Frequency (f)
- Amplitude (A)
- Phase (phi)
- Wavelength (lamda)
- Speed (v)
13
Q
What is frequency?
A
- Cycles per second (Hz)
- Inverse of period
- Determined by source characteristics
- Correlates to perceived pitch
14
Q
What is amplitude?
A
- Correlates to perceived loudness
- Instantaneous vs. average amplitude
- Root Mean Square (RMS) Amplitude
15
Q
What is phase?
A
- When a sine wave starts at some arbitrary time (time shifts)
- Measured in degrees or radians
- Little effect on perception
