Sound Waves: Characteristics and Applications

These flashcards cover the fundamental principles of sound, including its production via vibration, propagation through different media, wave characteristics such as frequency and wavelength, human perception, and technological applications like sonar and ultrasonography.

Vibration

The periodic to and fro motion (oscillations) of an object.

Source of sound

The object that produces sound.

Larynx

Commonly known as the voice box in the throat, it contains muscular flaps called vocal cords that vibrate to produce sound in humans.

Tuning fork

A U-shaped metal bar with a stem and two sides called prongs or tines, used for experiments to produce nearly single frequency sounds.

Medium

The material (solid, liquid, or gas) through which sound propagates.

Vacuum

A space containing no medium or matter where sound cannot propagate.

Compression (C)

A region of air where the density is higher than the average density due to particles being pushed together.

Rarefaction (R)

A region of air where the density is lower than the average density due to particles being spread out.

Sound wave

A disturbance consisting of a series of alternating compressions and rarefactions propagating through a medium without the actual flow of particles.

Longitudinal wave

A type of wave where the particles of the medium vibrate back and forth parallel to the direction of wave propagation.

Mechanical wave

A wave that requires a material medium for propagation, such as a sound wave.

Transverse wave

A wave where the particles vibrate in a direction perpendicular to the direction of wave propagation, such as light.

Crest

The highest point on a density-distance graph representing the maximum density in a compression.

Trough

The lowest point on a density-distance graph representing the minimum density in a rarefaction.

Wavelength ($\lambda$)

The distance between two consecutive crests or two consecutive troughs; its SI unit is the metre ($m$).

Frequency ($\nu$)

The number of density oscillations at a fixed point per unit time, measured in hertz ($Hz$) or $s^{-1}$.

Time period ($T$)

The time taken for one complete density oscillation at a fixed point, related to frequency by the equation $T = \frac{1}{\nu}$.

Amplitude

The maximum change in the density of the medium in a compression or rarefaction compared to the average density.

Intensity of sound

The amount of sound energy passing through a unit area perpendicular to the direction of propagation in a unit time.

Speed of sound ($v$)

The distance a point on a wave travels in unit time, calculated as $v = \lambda \times \nu$.

Pitch

The human perception of sound frequency; high pitch corresponds to high frequency (shrill sounds) and low pitch to low frequency (deep sounds).

Audible range

The range of sound frequencies humans can hear, roughly from $20\,Hz$ to $20,000\,Hz$ ($20\,kHz$).

Infrasonic waves

Sound waves with frequencies below $20\,Hz$, which humans cannot hear.

Ultrasonic waves

Sound waves with frequencies above $20\,kHz$, which are used in medical imaging and industrial cleaning.

Decibel ($dB$)

The unit commonly used to measure the loudness of sound.

Tone

A sound consisting of a single frequency.

Timbre

The quality of sound that allows us to distinguish between different instruments or voices playing the same note at the same loudness.

Octave

The interval between two notes where one note has double the frequency of the other.

Reflection of sound

The phenomenon where sound waves bounce off obstacles, following laws similar to the reflection of light.

Echo

The repetition of sound caused by reflection from a distant hard surface, heard only if the time gap from the original sound is at least $0.1\,s$.

Reverberation

The persistence of sound in a large hall due to multiple reflections arriving with a time difference of less than $0.05\,s$.

Echolocation

The ability of animals like bats and dolphins to locate objects by sensing the echoes of emitted ultrasonic waves.

Sonar

Acronym for Sound Navigation and Ranging, a technique using ultrasonic waves to determine the distance, direction, and speed of underwater objects.