Acoustics and the Physical Nature of Sound

Vocabulary flashcards covering foundational concepts in acoustics, sound wave properties, categories of acoustics, wave mechanics, speed, and pressure metrics based on Chapter 1.

Acoustics

The science of sound, traditionally referring specifically to the study of the physical nature of sound as a major division of classical physics.

Ultrasonics

Vibrations too fast for the human ear to detect, used for application such as calling dogs, detecting burglars, cleaning small machine parts, and studying crystal structures.

Infrasonics

Vibrations too slow for the human ear to detect, used by atmospheric physicists to study blast waves or weather systems.

Music

Intentional combinations of sounds chosen for esthetic enjoyment that usually depend on an orderly pattern of sounds for a pleasing effect.

Speech sounds

Sounds organized to communicate the entire range of human ideas through word symbols rather than by conveying emotions directly.

Noise

Sounds that are unorganized, unpleasant, or unwanted.

Pitch

The sensation of how high or low a sound is, corresponding to positions toward the right or left end of a piano keyboard.

Loudness

The human sensation of strength or weakness in a sound.

Treble

High-pitched sounds.

Bass

Low-pitched sounds.

Vibration

A rapid back-and-forth movement of a single object or of a single small piece of a large object.

Wave

A disturbance traveling outward in all directions from a vibrating source.

Compressions

Regions in a sound wave where the density and pressure of the air are temporarily greater than normal.

Rarefactions

Regions in a sound wave where the density and pressure of the air are temporarily reduced below normal values.

Transverse wave

A wave in which the local disturbance or particle motion occurs perpendicular (crosswise) to the direction of wave travel.

Longitudinal wave

A wave in which the vibration of each local parcel of material is aligned parallel (lengthwise) to the direction of wave travel.

Wavelength

The distance from one crest to the next along the direction of wave travel, represented by the Greek letter $\lambda$.

Rays

Arrows drawn perpendicular to wave crests to indicate the direction in which waves are moving.

Nondispersive medium

A medium in which all sounds, regardless of high or low pitch, travel at the same speed.

Dispersive medium

A medium in which waves travel at different speeds depending on their wavelength or frequency, such as water surface waves or light passing through glass.

Displacement amplitude

The distance each bit of air moves to either side of its normal position during its vibration.

Pressure amplitude

The maximum increase of air pressure above normal atmospheric pressure in a sound wave compression.

Newton

The metric unit of force, abbreviated as $\text{N}$, where approximately $4\frac{1}{2}\,\text{N}$ equal $1\,\text{pound}$ of force.

Pressure

Force exerted per unit area, defined mathematically as $p = \frac{F}{S}$.

One atmosphere

A unit of pressure representing normal atmospheric conditions, equal to approximately $10^5\,\text{N/m}^2$ (or $14.7\,\text{lb/in}^2$).