Sound Waves: Characteristics and Applications

Comprehensive vocabulary flashcards covering the characteristics, properties, mathematical formulas, and industrial applications of sound waves from the lecture.

Vibration

The periodic to-and-fro motion of an object about its mean position that produces sound.

Wave

A disturbance that travels from one place to another through a medium without the permanent movement of matter.

Wave Motion

The transfer of energy through a medium due to the vibrations of its particles about their mean positions.

Transverse Wave

A wave in which the particles of the medium vibrate perpendicular (up and down) to the direction of wave propagation, such as waves on a stretched rope.

Longitudinal Wave

A wave in which particles of the medium vibrate back and forth along the same direction in which the wave travels, creating alternating compressions and rarefactions.

Compression

A region in a longitudinal wave where the particles of the medium are closely packed together, resulting in high density and high pressure.

Rarefaction

A region in a longitudinal wave where the particles of the medium are spread apart, resulting in low density and low pressure.

Mechanical Wave

A wave that requires a material medium (solid, liquid, or gas) for propagation and cannot travel through a vacuum, such as sound.

Cochlea

A spiral structure in the human inner ear that converts amplified mechanical sound vibrations into electrical signals sent to the brain.

Wavelength ($\lambda$)

The distance between two consecutive compressions (crests) or two consecutive rarefactions (troughs), measured in metres ($\text{m}$).

Frequency ($\nu$)

The number of complete vibrations or oscillations per second, measured in Hertz ($\text{Hz}$).

Time Period ($T$)

The time required to complete one full vibration or oscillation, measured in seconds ($\text{s}$) and inversely related to frequency by $\nu = \frac{1}{T}$.

Amplitude ($A$)

The maximum displacement of vibrating particles from their mean position, which directly governs the loudness and energy carried by the wave.

Wave Speed Equation

The formula $v = \lambda \times \nu$, which relates wave speed ($v$) to wavelength ($\lambda$) and frequency ($\nu$).

Pitch

The characteristic of a sound that determines whether it is perceived as shrill or deep, depending directly on the frequency of the sound wave.

Loudness

The auditory sensation that describes how strong or soft a sound is, determined by the amplitude of the vibrating wave.

Intensity

The amount of sound energy passing through a unit area per unit time, which decreases as the distance from the source increases.

Timbre

The distinct quality of a sound that enables listeners to distinguish between different sources producing the same pitch and loudness, governed by source construction and overtone structure.

Reflection of Sound

The bouncing back of sound waves upon encountering an obstacle or boundary, following the rule that the angle of incidence equals the angle of reflection.

Echo

A distinct reflected sound heard separately from the original sound, requiring a minimum time separation of $0.1\,\text{s}$ and a reflective surface distance of about $17\,\text{m}$ in air.

Reverberation

The persistence of sound within an enclosed space resulting from multiple successive reflections off surfaces such as walls, ceilings, and floors.

Audible Range

The range of frequencies detectable by the normal human ear, spanning from $20\,\text{Hz}$ to $20\,\text{kHz}$.

Infrasonic Waves

Sound waves with frequencies lower than the human threshold of hearing (less than $20\,\text{Hz}$), produced by phenomena such as earthquakes and volcanic eruptions.

Ultrasonic Waves

Sound waves with frequencies exceeding the human audible limit (greater than $20\,\text{kHz}$), applied in medical imaging, flaw detection, and industrial cleaning.

Ultrasonography

A diagnostic medical imaging application that uses reflected ultrasonic waves to examine internal organs without surgery.

Ultrasonic Flaw Detection

An industrial testing method where ultrasonic waves pass through a solid block to locate internal defects and cracks by detecting premature reflections.

Echolocation

The sensory mechanism by which animals such as bats emit ultrasonic pulses and interpret returning echoes to map surroundings and locate prey.

SONAR

Sound Navigation and Ranging; a technology that transmits ultrasonic pulses underwater to measure the depth or distance of submerged objects using the time delay of reflected waves.