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40 Cards in this Set
- Front
- Back
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Sound Waves are Additive
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two pure tones added together; series of sound waves that are added together
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complex waves
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series of sound waves added together that might have different frequencies, phases, and amplitudes
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Joseph Fourier
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19th century mathematician that studied complex wave forms
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Fourier Analysis
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a complex wave form can be decomposed or analyzed to determine the amplitudes, frequencies, and phases of the sinusoidal components
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what determines if a complex wave is periodic?
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it has to be harmonic meaning the sine waves that compose it are whole number multiples of the fundamental frequency
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Fundamental Frequency=100 Hz
What is the 1st, 2nd, 3rd, and 4th harmonic? |
1st=100
2nd= 2x100 3rd= 3 x 100 4th = 4 x 100 |
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sawtooth wave
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a complex periodic waveform that has energy at the odd and even harmonics and a spectral envelope of -6 dB per octave
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square wave
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a complex periodic waveform that has energy at only odd harmonics and a spectral envelope of -6dB per octave
formed by adding fundamental frequency and odd harmonics |
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octave
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doubling or halving of frequency
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Time Domain
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instantaneous amplitude across time, amplitude = Y axis, time = X axis
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Frequency Domain
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more advantageous; requires the graphs of frequency and phase in order to recreate the wave; time is discarded because an infinitely repeating signal is assumed
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Triangular Wave
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a complex periodic waveform that has energy at odd harmonics and a spectral envelope of -12dB
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transient signals
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have a very rapid, fast onset and offset time; shorter durations
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the shorter the duration a signal is, the _____the spectrum
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wider
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what is an infinitely short signal called?
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an impulse response
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pulse train
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a repetitious series of rectangularly shaped "pulses" of some width or duration
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repetition frequency
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taking the reciprocal of the period of the pulse train
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Null Region
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occurs at integer multiples of the reciprocal of the pulse duration
Null= 1/Pulse Duration, 2/ Pulse Duration, etc |
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continuous spectrum
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has null regions; energy is across the spectrum not just at those null regions
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what part of a signal gives you the acoustic information you need to determine what the signal is?
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the leading edge
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What 3 different types of waves can you have?
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quasiperiodic, periodic, aperiodic
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What is a white noise wave an example of?
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an aperiodic wave
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White Noise
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aka gaussian noise; an aperiodic waveform with equal energy within any frequency band 1 hz wide and with all phases present in a random way
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does white noise have harmonics or frequencies?
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No
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how is white noise often created?
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by air turbulence
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Resonators
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reinforces the sound waves emanating from the vibrating strings
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What 2 characteristics of a sound source determine the frequency?
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mass and stiffness
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What are the different types of filters?
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high pass, low pass, band pass, band reject
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High Pass Filter
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passes high frequency and rejects the low frequency
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Low Pass Filter
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passes low frequency and rejects the high frequency
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Band Pass Filter
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passes information between 2 cutoff points
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As resonant frequency increases, mass reactance _______
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increases
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As resonant frequency increases, compliant reactance _______
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decreases
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What are the 5 parameters of a filter
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center frequency, upper cutoff, lower cutoff, bandwidth, attenuation rate
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center frequency
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the frequency that will result in maximum amplitude of vibration
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upper cutoff frequency
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the frequency above the center frequency for which the amplitude of response is 3dB less than the amplitude at maximum center frequency
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lower cutoff frequency
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the frequency below the center frequency for which the amplitude of response is 3dB less than the amplitude at maximum center frequency
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bandwidth
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the width of a filter measured in Hz; refers to the width of the band of frequencies between the lower and upper cutoff frequencies, and it defines the range of frequencies over which energy is passed by the filter
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attenuation rate
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the rate with which the amplitude of response is attenuated as a function of frequency
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idealized filter
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a filter that says everything below gets passed; everything else is rejected
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