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Sound Image 1

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jedi bunny

on 25 June 2017

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Transcript of Sound Image 1

- we hear before we see:
reactive listening begins at around 16 weeks, even though the ear is not fully developed until 24 weeks; sight is the last sense to be developed and is not fine-tuned until after birth; eyelids don't usually open until 7th month.

 - there is a difference between hearing and listening
 - we should develop an awareness of our sonic environment
 - we will learn to manipulate sound to tell a story or evoke a mood
 - sound has physical or acoustic dimension but still seems abstract
- sound engages imagination and emotions
- sound can be layered, the ear can process many sounds at once:
speech, noise, music
 - with film and video, the brain sees one image at a time
Acoustical phase:
The time relationship between 2 or more soundwaves at a given point in their cycles. Waves are repetitive and occur at regular intervals, which you can measure in degrees.

In phase
: If 2 identical waves begin at the same time, the intervals will coincide. They reinforce each other and increase in amplitude. This is constructive interference.
Out of phase
: If the 2 identical waves begin at different times, the intervals will not coincide and could decrease each other's amplitude. This is destructive interference.
specific color or tonality of diff sounds, despite being same pitch. Related to harmonics, material of vibrating object, how sound is made: struck, plucked, blown, etc.
Loudness: How the brain perceives amplitude

Decibels or dB: How we measure loudness

Sound Pressure Level or SPL: the relative intensity of acoustic pressure

Audible dynamic range: Humans hear from 0dB to 120dB, from quiet to deafening.

Threshold of hearing: quietest sound we can hear
Threshold of pain: loudest sounds we hear, causes pain & hearing loss
number of cycles the vibrating object completes in one second.
Cycles per second are expressed in hertz or kilohertz.

Audible frequency range:
About 20hz to 20kHz  Frequencies at high and low end are felt rather than heard.

The way the brain perceives frequency; highness or lowness; treble or bass.
 The air molecules don't move with the wave, they eventually slow down and settle into an average resting place until another wave comes.

As vibrating object moves outward, it squeezes air molecules together - increasing air pressure
: As vibrating object moves inward, pulls air apart and thins out molecules - decreasing air pressure

When a vibration has undergone one back and forth motion it completes one cycle.
The Sense of Hearing
Sound Envelope
: Changes in loudness or volume over time
- first sound emitted when object starts vibrating
initial decay
- slight decrease in amplitude as sound reaches momentum
- how long the sound stays at stable amplitude or volume; the body of the sound
final decay or release
: how long it takes for sound to go from stable vibration to silence

The diagrams we've been looking at are simple soundwaves, pure tones called
sine waves
But sound consists of several frequencies at various amplitudes with a unique structure. This is a
complex or composite waveform

Harmonics: whole number multiples of the fundamental frequency
Equal Loudness Principle:
We do not hear high and low frequencies at equal loudness as midrange freqs.
Our ears are most sensitive at 3kHz - you'd have to boost a sound 70dB to hear lower, bassier frequencies.

The length of one cycle, from one point of compression to one point of rarefaction.
Example: 20 Hz wavelength is 55 feet; 8kHz is 1.5 inches
Short high freqs bounce; long low freqs bend.
Sound is created by a vibrating object. Air molecules closest to the object are set in motion. A sound wave is created as these molecules move back and forth in response to vibration. Momentum is transferred to adjacent molecules and propagates the wave, carrying sound to your ear. This is possible because of the elasticity of air itself.

Harmonic Partials

- when one object vibrating at the same natural frequency of a second object forces that second object into vibrational motion.
An acoustically resonant object usually has more than one resonance frequency, especially at its harmonic frequencies. 
It will easily vibrate at those frequencies, and vibrate less strongly at other frequencies. It will
"pick out"
its resonance frequency from the sound waves around it. In effect, it is filtering out all frequencies other than its resonance.
Speed of Sound
In common everyday speech, speed of sound refers to the speed of sound waves in air. However, the speed of sound varies from substance to substance, and with temperature. Sound travels faster in liquids and non-porous solids than it does in air, and faster in warmer temps than in cold.
In dry air at 20 °C (68 °F), the speed of sound is 343.2 metres per second (1,126 ft/s).
In fresh water, sound travels at about 1497 m/s at 25 °C.
In salt water that is free of air bubbles or suspended sediment, sound travels at about 1560 m/s.
In brick, sound travels at 4176 m/s; in steel at 6100 m/s; and in glass at 3962 m/s.
basic ideas about sound
relates to knowledge, reasoning, memory and judgement
relates to feelings and emotions
 frequency bands:

low bass - 20 to 80Hz - power, boom, fullness
upper bass - 80 to 320Hz - foundation freq, warmth
midrange - 320 to 2360Hz - intensity and presence
upper midrange - 2kHz to 5kHz - clarity/definition, speech
treble - 5kHz to 20kHz - brilliance, hiss
Amplitude: A measure of acoustic pressure or how many
molecules are being moved by a vibrating object.
The size of the sound wave.
Full transcript