7L Sound Flashcards
Making Sounds
Sounds are made by something vibrating.
Intensity
How loud or soft a sound is- its volume.
Pitch
How high or low a sound is.
Frequency
The number of vibrations each second.
The higher the frequency the higher the pitch.
Hertz (Hz)
The units for measuring frequency.
Amplitude
The size of vibrations.
The bigger the amplitude the louder the note.
Humans Making Sounds
Two flaps (vocal folds) across the windpipe vibrate when air moves across them.
Grasshoppers Making Sounds
Male grasshoppers chirp by rubbing one leg against a wing.
Gorillas Making Sounds
Male gorillas thump their chests or thump the ground to threaten other males.
Moving Sounds
Sounds can only travel through a medium (a solid, liquid or gas).
Vacuum
A completely empty space. Sound cannot travel through.
Particles
Tiny pieces of matter that make up everything.
Sound Moving Through the Air
Air particles vibrate and cause nearby particles to vibrate so the vibrations spread through the air.
Sound Wave
Formed by the moving vibrations.
Pressure Wave
The air particles are pushed together in some place (high pressure) and spread out in other places
Sound Wave Frequency
The number of waves passing a point per second.
Sound Wave Amplitude
The distance moved by air particles as the sound wave passes.
Energy
Energy is transferred from one place to another by sound waves. They do not transfer particles.
Speed of Sound
Sound travels faster in solids because the particles are close together.
Moving Away from A Source
As you move away from a source of sound, the energy carried has spread out further so there is less energy for your ear to detect- it sounds quieter.
Ear Protection
Loud sounds damage our ears- people who work in noisy surroundings need ear protection. Certain soft materials (carpets, curtains, etc.) also absorb energy transferred by sound waves.
How Ears Detect Sounds
sound waves enter the ear canal.
the eardrum (a thin membrane) vibrates.
vibrations pass to the tiny bones which amplify the vibrations.
vibrations pass to the liquid inside the cochlea.
tiny hairs inside the cochlea detect vibrations and create electrical signals (impulses).
impulses travel along the auditory nerve to the brain.
How Microphones Detect Sounds
Sounds make a thin sheet of materials (a diaphragm) vibrate and electrical circuits convert these vibrations into electrical currents.
Decibels (dB)
The units for measuring the loudness of a sound.
Auditory Range
The range of frequencies an organism can hear
20Hz – 20000Hz in humans
Infrasound
Sounds below 20Hz
Ultrasound
Sounds above 20000Hz
Using Sound
Sound is often used for communication.
Transmitted
Energy from sound waves goes through some materials.
Reflected
Energy from sound waves bounces off some materials.
Using High Frequency Waves
Treat injuries
Clean delicate objects by making tiny bubbles that loosen dirt when the burst.
Echo
A reflected sound
Echolocation
Used by animals (bats, dolphins, etc.) to find their way around/find prey.
Sonar
Pulse of ultrasound is given off and reflected by the sea bed. It is then detected by sonar equipment to find the depth.
Longitudinal Waves
Particles vibrate in same direction wave is moving.
Transverse Waves
Particles vibrate at right angles to direction wave is moving.
Superposition
As waves pass through each other their effects add up or cancel out.
