Music tech quiz 1

Sound

Energy produced when objects vibrate; disturbance of a medium

Air pressure

Density of air mollecules

Acoustic

Of or pertaining to sound, the sense of hearing, or science of sound

Compressed state

Air molecules pushed together, greater pressure

Rarefied state

Air molecules spread apart, lower pressure

Atmospheric pressure

Pressure associated with weather; greater magnitude, changes slower

Sound pressure

Pressure associated with acoustics or music; lesser magnitude, changes quicker

Wave fronts

Flat rings of energy that expand outwards from an energy event

Plane wave

Flat tended property of sound waves

Transverse waves

Waves that vibrate perpendicular to wave’s propagation (ex. water waves)

Longitudinal waves

Waves that vibrate parallel to wave’s propagation (ex. sound waves)

Oscilloscope

Testing device that displays electrical wave form signals

Zero line

Where there is no change in pressure from undisturbed pressure level

Periodic waveform

Wave that is regular, repeating, sounds like a tone

Aperiodic waveform

Wave that is irregular, not repeating, unpredictable

Cycle

One interation of a repeating pattern

Period

Amount of time it takes to complete one cycle

Wavelength

Distance travelled to complete cycle

Phase

Starting point of a cycle

Timbre

Tone quality/color; determined by spectrum

Vibrating systems

System where motion is repetitive and returns to particular position at regular intervals

Time domain plot

Graph that shows pressure level changes over time

Restoring force

Force that acts to bring object back to rest

Simple harmonic motion

Vibrating systems that display a sine wave

Waveshape

Shape of a wave (ex. sine, square, sawtooth)

Polarity

Wave’s up or down orientation

Amplitude

How high a wave gets (maximum displacement of air molecules)

Wave diffraction

Dimensions of surface are smaller than wavelength (wave bends around object)

Wave reflection

Dimensions of object are larger than wavelength (wave bounces off object)

Pitch

Perception of frequency

Principle of superposition

Value of total wave = sum of values of individual waves

Fundamental frequency

Lowest frequency an object can support; what we hear most clearly

Harmonic series

Higher frequencies layered on top of the fundamental

Harmonic frequency

Harmonic number x fundamental frequency (Hz)

Standing wave

Wave that oscillates back and forth

Nodes

Places where air molecules do not move (stay at equillibrium)

Antinodes

Places where air molecules are at maximum displacement

Resonant frequencies

A string’s set of frequencies that produce standing waves

Frequency

How often a wave repeats (vibrations/sec)

Quarter-wave resonators

Tube that supports a fundamental frequency 4x the length of tube (open on one end, closed on other)

Half-wave resonators

Tube that supports a fundamental frequency 2x the length of tube (open or closed on both ends)

Resonance

Property of high efficiency from a small input

Sympathetic vibration

Vibrations passed from one object to another via air molecules

Resonators

Objects resonance is passed between

Mechanical coupling

Vibrations is passed between objects via physical contact

Chlandi patterns

Patterns of complex vibrations; illustrated in sand

Out of phase

Two waveforms at same frequency that do not have simultaneous zero crossings

Sinusoidal waves

Smooth, repeating wave shapes (ex. sine waves)

Speed of sound

1125 ft/sec in air

Air particle velocity

Speed at which individual molecules move

Fourier transform

Transforms sound into spectral domain representation

Equal temperment

Tuning by standing waves

Just intonation

Tuning based on fundamental frequency

Wave interference

2 or more waves overlap in the same region

Constructive interference

Waves add together

Deconstructive interference

Waves cancel each other out

Reverb

Sound reflecting off walls in enclosed space