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### 42 Cards in this Set

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 What is the difference between compression and rarefaction of a sound wave? Compression is the part where air molecules are very dense (compact) and rarefaction is where molecules are very sparse Describe a longitudinal wave The particle movement is parallel to the wave movement Describe a transverse wave The particle movement is perpendicular to wave direction Does speed of sound travel faster or slower in hot air? Why? Sound travels faster in warm air because warm air is less dense than cold air What type of wave describes propagation of sound? Longitudinal waves In which medium does sound travel the slowest? air, helium, water, or steel Air moves at about 1130 fps at room temperature Which frequencies are able to bend around corners the easiest? Describe the wavelengths of these frequencies Low frequencies bend the easiest because the long wavelengths allow them to bend around corners without much attenuation Which unit is sound power normally expressed in? picowatts or pW Which unit is sound pressure normally expressed in? micropascals Describe the difference between spherical waves and plane waves As spherical waves spread, intensity falls off inversely as the square of the distance (inverse square law). There is no spreading with plane waves and no intensity change with distance What is sound pressure at nominal threshold? Why? 20 micropascals, which is the average sound pressure required to reach threshold at 1000 Hz for a young adult from a screened population What is the main reason to use a decibel scale to express the level of sound? Decibels compress the large range of numbers What decibel change is a just noticeable difference (JND)? 3 dB What decibel change is a doubling of loudness? 10 dB Describe difference between periodic and aperiodic waves A waveform that repeats itself is periodic. An aperiodic wave includes all frequencies and does not repeat itself To cancel a tone, a second tone must be sounded that meets which condition? same frequency, same amplitude, and opposite phase vocal fold vibration is modeled as a periodic wave with which kind of harmonics? Speech contains odd and even harmonics What is the term for the gradual decline in the amplitude of simple harmonic motion? damping what is the formula for sound pressure level in decibels? 20 log (P/Pr) What is a wave which does not encounter a reflective surface? free progressive wave What is a pure tone? sound from a single frequency What kind of noise is produced by a broad band of frequencies? white noise What occurs when the driving frequency of one system matches the natural frequency of a vibrating system? resonance What type of resonance occurs when a tuning curve is tall and narrow? sharp resonance what is the beat frequency of two tones at 2024 Hz and a 2030 Hz? 6 Hz What 3 characteristics describe a filter? center frequency, bandwidth, attenuation rate (slope) What attenuation (in decibels) does the inverse square law provide? 6 dB per doubling of distance What term describes when sound waves bend due to a temperature inversion? refraction What term describes when sound bends around the corner of a building? diffraction The nodes on a vibrating string are points where there is what kind of motion? no motion What type of room would a free progressive wave be found? anechoic room What is it called when the distance from a source in a room where the direct sound is equal to the reverberant sound? critical distance What is the definition of reverberation time? The time it takes for sound to decay by 60 dB What component of every vibrating system causes damping to occur? What is this force named? Component = resistance Force = friction The bandwidth of a filter is the difference between what 2 frequencies? The upper frequency cut-off and the lower frequency cut-off Describe the effects of concave and convex surface to sound Concave surface bends toward incident sound and focuses the sound and convex surface bends away and scatters the sound What type of room would a free progressive wave be found? anechoic room What is it called when the distance from a source in a room where the direct sound is equal to the reverberant sound? critical distance What is the definition of reverberation time? The time it takes for sound to decay by 60 dB What component of every vibrating system causes damping to occur? What is this force named? Component = resistance Force = friction The bandwidth of a filter is the difference between what 2 frequencies? The upper frequency cut-off and the lower frequency cut-off Describe the effects of concave and convex surface to sound Concave surface bends toward incident sound and focuses the sound and convex surface bends away and scatters the sound