Echoes, Sound Waves, and Hearing

A complete list of vocabulary terms and definitions covering sound wave properties, ear structure, wave calculations, echoes, and wave behavior from the provided lecture material.

Echo

A sound wave that reflects off a surface and returns to the ear.

Hard, Smooth Surfaces

Surfaces that are effective at reflecting sound waves and creating echoes.

Soft Surfaces

Surfaces, such as carpets and curtains, that absorb sound waves to reduce echoes.

Distance Travelled by an Echo

Calculated as $2 \times \text{distance to the reflecting surface}$, because the sound wave travels to the surface and back.

SONAR

A sound navigation method used by ships to detect the depth of the sea floor using sound wave reflections.

Pinna

The visible outer portion of the human ear.

Eardrum

A thin flap of skin stretched tight like a drum that vibrates when sound waves reach it.

Ear Bones (Ossicles)

Three small ear bones—the hammer, anvil, and stirrup—that pass vibrations from the eardrum to the cochlea.

Cochlea

A spiral-shaped part of the inner ear resembling a snail shell that converts mechanical vibrations into electrical signals.

Auditory Nerve

The nerve responsible for transmitting electrical signals from the cochlea to the brain.

Ultrasound

Sound waves with a frequency higher than $20000\text{ Hz}$ ($20\text{ kHz}$), which is above the maximum frequency human ears can detect.

Perfect Pitch

The rare ability to identify exact musical notes upon hearing them without reference.

Oscilloscope

An electronic device with a visual screen that, when used with a microphone, measures and displays properties of sound waves.

Superposition

The interaction resulting when two waves occupy the same place at the same time, combining their amplitudes where peaks meet peaks, or canceling out where peaks meet troughs.

Noise Cancelling Headphones

Headphones that utilize wave superposition by matching ambient sound wave peaks with wave troughs to cancel out background noise.

Displacement

The distance of a point on a wave from its rest position.

Wavelength

The distance from peak to peak, or across one full complete cycle of a wave.

Amplitude

The maximum displacement of a wave from its rest position.

Peak (Crest)

The highest point or top of a wave.

Trough

The lowest point or bottom of a wave.

Rest Position

The central position of a wave when no wave disturbance is present.

Frequency

The number of complete wave cycles per second, which dictates the pitch of a sound wave.

Loudness

A sound characteristic determined by the amplitude of the sound wave and measured in decibels ($\text{dB}$).