Exam 2 Flashcards
Frequency
- Rate of vibration of an object
- # of cycles occurring in an amount of time
- Unit: Hertz (Hz; cycles/second)
Period
- Amount of time it takes for one cycle in a wave to complete
- Unit: s, ms
Euqations for Frequency/Period
Reciprocal relationship/inverse; you can find one if you have the other.
Periodic sounds
- Sounds with a regular, repeating pattern
- each cycle takes the same time to occur (period)
- pressure changes (amplitude) are equal for all cycles
Aperiodic sounds
No regular, repeating pattern
- cycles do not take the same amount of time to ocur
- sounds like noise
Waveform
A graph with time on the horizontal (X) axis and amplitude on the vertical (Y) axis. Shows…
- movement over time
- increases/decreases in air pressure
Wavelength
The distance it takes for one cycle to occur.
Equation for wavelength
Inverse relationship between wavelength and frequency (higher frequency = shorter duration of period = shorter wavelength)
- v = speed of sound; stays constant as long as you don’t change the medium
Incedent wave
A sound wave that is generated, travels a certain distance, and then hits up against a boundary.
Boundary behaviors: transmission
Sound passes through the boundary
Boundary behaviors: Absorption
Damping of a wave with diminishing changes in air pressure due to friction.
Boundary behaviors: reflection
Some portion of the sound that is not transmitted or absorbed bounces back from the surface of the boundary and travels in the opposite direction of the incident wave at the same speed.
Boundary behaviors: diffraction
Sound bends around an obstacle without going through the boundary.
Boundary behaviors: refraction
Sound bounces back from the surface of a boundary in a different direction, speed & angle.
Interference
Occurs when 2 or more waves combine with each other in terms of areas of high and low pressure.
Constructive interference
Waves combine, reinforce each other, and increase the resultant amplitude
- sounds are in phase
Deconstructive interference
Waves combine and decrease the resultant amplitude
- sounds are out of phase
Complex interference
Effect depends on the degree to which the two waves are in or out of phase
(pic: some areas of decreased/increased amplitude)
Reverberation
Generates a sound that lasts slightly longer due to the interaction of intecedent and reflected waves
Simple Harmonic Motion (SHM)
A smooth back and forth movement with a characteristic pattern of acceleration through the rest position and deceleration at the endpoints of movement.
- generates a pure tone
Pure tone
A sound wave that has only one frequency
- generated by an object vibrating in SHM (Ex: tuning fork)
Complex sound
A wave consisting of two or more frequencies
Two types: periodic & aperiodic
Complex periodic sounds
Consist of a series of frequencies that are systematically related to one another.
- lowest frequency is fundamental frequency (F0), or first harmonic
- multiples of F0 are harmonic frequencies
Fourier analysis
Mathematical procedure to identify the individual sinusoids in a complex sound.
- plots amplitude (Y axis) vs. frequency (X axis)