Day 5: Introduction to Sound - Vocabulary Flashcards

Vocabulary flashcards covering key concepts from the video notes on sound, including wave types, speed, reflection, refraction, resonance, echolocation, and related phenomena.

Sound

A longitudinal wave that travels through air by vibrating compressions and rarefactions; typical speed ~340 m/s in air at 20°C.

Longitudinal wave

A wave in which particles move parallel to the direction of travel; example: sound in air.

Compression

Region in a longitudinal wave where particles are pushed together, creating high pressure.

Rarefaction

Region in a longitudinal wave where particles are spread apart, creating low pressure.

Speed of sound

Rate at which sound travels; about 340 m/s in air at 20°C; increases ~0.6 m/s per 1°C rise above 0°C.

Echo

A reflected sound that returns after bouncing off a surface; multiple reflections become reverberations.

Reflection

The bouncing back of a wave when it hits a surface; angle of incidence equals angle of reflection.

Reverberation

Multiple echoes from successive reflections within a space.

Diffuse reflection

Reflection from a rough surface in many directions.

Refraction

Bending of a wave as it passes into a medium with a different speed.

Refraction of sound

Sound waves bend when parts of the wave fronts travel at different speeds due to wind or temperature gradients.

Ultrasonic waves

Sound waves with frequencies above human hearing (>20 kHz), used by animals in echolocation.

Echolocation

Biological sonar in which animals emit sound pulses and listen for echoes to locate objects.

Sonar

Sound Navigation and Ranging; underwater use of reflected sound to locate objects.

Oscilloscope

An instrument that graphs pressure versus time to visualize sound waves.

Natural frequency

An object's own vibration frequency, determined by its elasticity and shape.

Forced vibration

Vibration of an object produced by an external vibrating force.

Resonance

When impulses drive a vibrating object in rhythm with its natural frequency, producing large amplitude vibrations.

Tacoma Narrows Bridge collapse

A famous example where resonance caused the bridge to fail in 1940.

Elasticity

Property describing how readily an object deforms and returns to shape; affects natural frequency.

Shape (of an object)

The geometry of an object that influences its natural frequency.

Order of speeds of sound in media

Increasing speeds: air (~340 m/s); warm air faster; water ~4× air; steel ~15× air.

Speed of sound and temperature

Speed of sound increases by about 0.6 m/s for each 1°C rise above 0°C.

Radio waves vs sound waves speed

Radio waves travel much faster than sound waves (near the speed of light); sound travels ~340 m/s in air.