COGS 123M ch. 2

acoustics

the science of sound; including the production, transmission, and reception of sound

architectural acoustics

scientific study of how to achieve good sound within buildings

bio acoustics

studies the hearing and calls of animals, and how animals are affected by sounds in their environment

environmental acoustics

concerned with noises caused by traffic, aircraft, and other industrial equipment

musical acoustics

focuses on how musical instruments produce sound, how room design and sound reproduction processes affect musical sound and perception of that sound as music

how does sound occur

in waves

how do sound waves occur

when the vibration of an object causes changes in the air pressure around the object

expansion phase of a sound wave

the diaphragm moves inward, causing air molecules nearby to decrease in density, as well as air pressure decreasing; aka rarefaction

compression phase of a sound wave

the diaphragm moves outward, causing air molecules nearby to increase in density, as well as air pressure increasing; aka condensation

sound waves

pattern of air pressure changes (compression and expansion) alternating between high and low pressure regions in the air hundreds/thousands of times per second that propagates itself through the air

tuning fork

device used to tune instruments; when struck, vibrates in a consistent manner creating a tone of a specific pitch

what sound waves are produced by tuning forks?

simple sound waves known as pure tones

pure tones

created by tuning forks; simple sound waves that are comprised of/produce sine wave vibrations

are most sounds pure tones?

no, most are complex waves (have irregularities)

frequency

refers to how frequently a sound wave goes through a complete high-low pressure cycle; how many times per second a sound wave goes through this cycle

how is frequency measured?

hertz (hz)

what is one hertz equivalent to?

1 cycle per second

what aspect of a sound wave is affected by frequency?

pitch; the higher the it is, the higher the pitch and vice versa

amplitude

refers to the size/difference of the air pressure changes; the greater it is the greater the difference between high and low peaks of a sound wave, and vice versa

peak amplitude

measure of amplitude between the high-pressure peak of the wave, and the surrounding/atmospheric air pressure

peak-to-peak amplitude

measure of amplitude between the high and low peaks of a wave

what aspect of sound waves are determined by amplitude

volume/loudness; the greater it is, the higher the volume, and vice versa