sound and its measurements

• a compressional wave that can be described as
• 1) psychologically aka an auditory experience
• 2) physically- a series of disturbances of molecules

the principle prerequisite for sound

• the transmitting medium and sound source.
• the medium most have mass and elasticity

the ability of an object to resist changes in shape or volume. The more densely packed molecules the more springier.

• Pitch is consistent when striking a tuning fork.  The only variables that change are the vibrations(amplitude) and the loudness. 
• - mass and elasticity dictates how the fork osscilates

• At rest the tuning fork has kinetic energy
• at the centre and beyond resting the tuning fork has potential energy

the simplest of all sound waves

allow us to represent a sound wave mathematically

• 1)phase
• 2)amplitude
• 3)frequency

used to describe the starting position of the sound or the phase relationship between 2 or more sounds.  Can have the same amplitude and frequency but different phases

Localization

two sine waves add together

is when two sine waves cancel each other out resulting in no signal.  This happens when sine waves start at opposite phases

measures of strength and magnitude of sound wave.  Measures in sound pressure. It relates to the force being applied to the source

maximum peak to maximum trough measurement

the average of many points on a sine wave

the rate at which a sine waves repeats itself over time. How much does it vibrate per second? f=1/T T=1/F

20 hz to 20,000 but our best hearing is 1000-4000 Hz. Hearing tests show sensitivities from 250 Hz to 8000 Hz

• -influenced by the temperature and how dense the medium is. The tighter the molecules are packed the faster sound can travel.
• -not related to hertz

• inverse relationship. When wavelength increases freq decreases and when freq increases wavelength decreases
• -as speed of sound increases the wave length increases

the thicker a walls needs to be to attenuate it.  When we test normal hearing at 20Hz we need to be in a room with thick walls.

the frequency does not change so we hear the same pitch

as it approaches you the pitch gets higher then lower as it passes you (doppler affect)