# CDO 463 1 Basic Acoustics

 sound narrow definition sensation for hearing sound broad definition physical quantity with vibration - periodic or aperiodic - and a pressure disturbance - compressions and rarefractions - and a medium - material for transmitting the sound periodic regularly repeating ex) tone repeats the same frequency aperiodic not reguarly repeating 2 types - turbulent and static ex) noise, bullistic, release of stop consonants Simple Harmonic Motion tuning fork produces the simpliest type of sound tine movement : X-Y-X-Z-X-Y-X-Z-Xone cycle: X-Y-X-Z-X Period / frequency amount of time for one cycle / # cycles per second frequency = 1/period or f=1/Tphysical dimension - observable and measurable Hz pitch the perception of frequency relationship between frequency/period and pitch increase in frequency = increase in pitch not a 1:1 change/dimensionsame physical change does not equal the same perceptual change amplitude force or pressure of sound related to displacement of tine loudness perception of amplitudedecibel dB relationship between amplitude and loudness increase in amplitude = increase in loudness not a 1:1 dimension Simple Harmonic Motion Uniform Circular Motion another type of SHMcircle of radius r point P moves around circle at a uniform speedat each new P, a new radius r' is drawn that forms an angle (theta) with the original rby the time P goes around the circle, theta will go from 0 to 360 degrees phase refers to the angle of theta period time for one revolution frequency # cycles/second amplitude the radius of the circle Amplitude (X) varies with the sine of theta X = r * sine waveform graph of displacement as a function of timethe waveform associated with SHM is the sine wave because the formula contains the sine function spectrogram includes time amplitude frequency spectrum includes amplitude frequency Simple Harmonic Motion Pendulum velocity is zero / movement stops at the extremesvelcoity is at its max at the point of rest amplitude graph vs. velocity graph the amplitude graph is alays 90 degrees behind the velocity graph superpositioning of sound waves adding sine waves togethergo point by point on the x axis and add the y axis numbers together adding sine waves of equal frequency results in a sine wave with the same frequency creates simple waves adding sine waves of different frequencies results in complex waves - any wave that is not a sine wavea wave with more than one frequency component square waves are formed by adding the odd multiples of a given frequency the fundamental frequency is the lowest frequency largest comon multiple in a series of frequencies harmonics frequencies that are integer multiples of the fundamental frequency Authorshanamd2011 ID169879 Card SetCDO 463 1 Basic Acoustics DescriptionBasic Acoustics: Sound Generation and Propagation Updated2012-09-09T21:57:52Z Show Answers