Sound Properties Flashcards
Air
Made up of molecules and spaces between these molecules
Elasticity
A property of air that causes air molecules that have been compressed together to spring apart.
Expl. Blowing up a balloon compresses the air molecules inside the balloon. When the balloon is popped, the air molecules spring apart.
Compression
Occurs when air molecules are pushed together by a sound source.
Expl. Pulling back a guitar string and letting it go.
Rarefaction
The area where there are fewer molecules than before because of the compressions.
Compression Waves
A series of compression and rarefaction that propagate(move) through the air.
Sound
Compression waves created by a vibrating body including:
- Strings
- Mouthpiece(brass / wood instruments)
Vocal Chords
Sampling*
Recording real sounds and making them available on the keyboard
Resonance
When the initial sound wave is passed through the body of an instrument in order to modify its pitch and timbre.
Example: The body of a violin or guitar is a resonator for the sound waves created by the strings.
The Human Ear
Allows us to hear compression waves and can be divided into 3 basic parts:
- Outer Ear
- Middle Ear
- Inner Ear
The Outer Ear
Consists of the Pinna and the Ear Canal.
Pinna
The flesh on the outside of your head. It helps us locate the sound source and slightly filters the sound.
Ear Canal
The length and shape of the ear canal emphasizes frequencies between 2,000 - 5,000 Hz
The Middle Ear
Consists of the tympanic membrane (eardrum).
Eardrum
Vibrates sympathetically with the incoming sound waves.
Example: A loud instrument played toward the head of a drum will cause the rum to vibrate without being struck.
The Inner Ear
Consists of the Cochlea
Cochlea
A fluid filled tube that is coiled up like a snail. The fluid in the cochlea vibrates an converts the vibration into neural impulses that are sent through the auditory nerve to the brain.
Hearing Loss
Age and exposure to loud sounds cause the cochlea to become gradually less receptive to high frequencies.
Physical Properties
The measurable properties of sound.
Example: Frequency is a physical property and is measured in Hz.
Perceptual Properties
Are created by the brain in response to the physical properties of sound.
Example: Pitch is the perceptual property associated with frequency.
Frequency (Physical Property)
Is the rate at which a sound moves through a full cycle.
Waveform view
A graph of the change in air pressure at a particular location in time. It shows compression and rarefaction.
Hertz(Hz)
the unit used to measure frequency
Human Audio Range
The range of frequencies that humans are able to perceive as sounds. The human audio range is 20 Hz to 20,000 Hz (20 kHz). Human audio ranges vary from person to person and decrease over time, losing high frequencies.
Ultrasonic Frequencis
Are above the human audio range.
