Hearing Science

the density of the air (the more molecules there are per unit volumte, the greater the number of collisions and the greater the pressure)

the temperature of the air (the higher the temperature the faster the air molecules move)

air molecules near the surface of the earth that have been squashed together to create a pressure of about 100,000 newtons per square meter

N/(m squared)

vibrating obj. moves out; air molecules are pushed away + squeezed tog. creating increase in density and pressure

vibrating obj. moves in; air molecules spread out to fill space vacated + create decrease in density and pressure

pressure variations; composed of alternating condensation and rarefaction; can propogatein all directions in 3dimensional space;longitudinal

330 meters per second (m/s); 740 miles per hour

steel (5200 m/s) because it is still. Rubber is dense and not still and sound travels at 54 m/s

1500 m/s even though water is denser than air (ususally slowing) it is much stiffer (accelerating)

pure tone

varies sinusoidally with time; x(t)= Asin(2(pie)ft+0)

varies sinusoidally with time; x(t)= Asin(2(pie)ft+0)

x(t) is pressure variation over time; A is peak amplitute (or pressure); f is crequency and 0 is starting phase

produces a waveform taht varies up and down over time between plus and minus one

number of cycles of the pure tone (alternate condensation and rarefaction) that occur at a given location during a given length of time

treble; bright sounds

bass; warm sounds

the unit that measures the frequency of a sound. measured in cycles per second; Hz

corresponds to the # of times in each second the air pressure alternates between high and low (high freq often measured in kilohertz [kHz])

inverse of frequency; it is the time taken for the pure tone to complete one cycle of alternative condensation + rarefaction

physical distance that is covered by a complete cycle of the sound wave; simple function of the frequency of sound

speed of sound divided by the frequency of the sound wave; higher the frequency, the shorter the wavelength + vice versa

phase of pure tone is the point reached on the pressure cycle at a particular time; covers range of 360 degrees or 2(pie) radians)

are relative

when a waveform crosses zero and is rising

when a pure tone starts at a positive zero crossing

if a pure tone starts at a peak

the magnitude of the pressure variations, measured with respect to the deviation from atmospheric pressure

the pressure at the peak of the waveform cycle

the amplitude; the square root of the average over time of the individual pressure variations squared

is equal t the root of 2 (i.e. 0.707) times the peak pressure

depends on the distance the object has to move during each cycle + the # of times it has to make this movement every second

the sound energy passing through a unit area (e.g. a square meter of air) every second

the energy transmitted per second

watss (units of power) per square meter (W/m(squared))

proportional to the square of rm pressure so that: I= kP (squared); I is intensity, P is rms pressure and k is a constant