Unit+3+Notes

Sound is in waves, heard by vibrations

Compression - high pressure air molecules pushed together, positive polarity

Rarefaction - low pressure air molecules pulled apart

Rarefaction and compression cancel each others' sounds out

Waves similar to sound waves, amplitude is how loud sound is, wavelength determines pitch,

Must tie sounds together when it is at a "zero crossing", otherwise it creates a clip

Sound is a longitudinal wave

Transverse waves go up and down

Longitudinal waves go back and forth




 * Pitch**

Pitch is determined by the wavelength of the sound, cycles / seconds, positive to negative back to positive polarity, period, cycle

Number of repetitions per second called frequency, measured in a unit Hertz (Hz.)

Tuning A has frequency 440, one octave higher 880, double frequency and you get the octave

Human's hearing range is 20 hz to 20,000 hz (20 khz)

Low frequencies travel further


 * Decibels (Amplitude)**

Higher the waveform, the greater the amplitude, the lower, the quieter

Softest sound a person can hear characterized as as 0 decibels

120 dB human pain threshold

** When a notes is played, playing notes above it infinitely upwards, 100hz also plays 200hz, 300hz, 400hz, actually note you hear is called the fundamental, other sounds called harmonics
 * Timbre

Sine waves are ONLY the fundamental, no harmonics present

Square wave consists of only the odd harmonics, all frequencies mathematically related, if another one added then the frequencies would be much more scattered

Triangle wave also only has odd harmonics, triangle wave high harmonics fall out faster that on a square wave, decrease in amplitude in upper harmonics

Sawtooth wave consists of all harmonics, very bright timbre to it

All frequencies played at the same time create Noise White noise, every frequency heard at the same amplitude Pink noise tapers off, high frequencies aren't prevalent

High sounds sound louder than low noise, pink noise is more balanced as it makes the higher frequencies quieter

Noise generation for room testing to test speakers, acoustics, and sound replication or enhancement

Timbre - (tone quality) Determined by the amplitude of the harmonics that are present in the sound

Harmonics are determined by whole number multiples of fundamental's frequency

Chord in music theory, playing sounds where they share harmonics


 * Doppler Effect**

As sound approaches, moving towards you fast, waves get closer together because source is moving towards you, higher frequency, then they are more spread apart when it is moving away from you, lower frequency