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32 Cards in this Set
- Front
- Back
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What is the relationship between compression and rarefaction?
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Compression is Air particles moving closer together by an external force. Rarefaction is moving farther apart by an external force than it is when in a state of equilibrium.
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What is Rarefaction?
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Waves of less than atmospheric pressure. Air particles moving farther apart by an external force than it is when in a state of equilibrium.
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What is Compression?
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Waves of greater than atmospheric pressure. Air particles moving closer together by an external force.
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How does sound differ from other vibrating motion?
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In two ways:1) Sound waves in free air are three dimensional. 2) Sound in air is propagated as a longitudinal wave, for example, air molecules lie in the direction of propagation.
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What mediums does sound operate? What objects create sound?
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Sound mediums must have mass and be compressible.
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What is Wave length?
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The distance in feet between identical points on two adjacent waves. Wavelength = C/f.
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What is period?
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The period of a vibrating body is the time elapsed during a single complete vibration.
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What is frequency?
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The number of complete vibrations or cycles per unit time and is usually measured in vibrations and cycles per second.
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What is Db? (Decibel)
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A quantitative unit of relative sound intensity or sound pressure based on the logarithmic relationship of amplitudes or pressures of two sounds, one of which serves as a reference.
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What are Pascals?
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The unit of sound pressure. One pascal is equal to one Newton per square meter.
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What are Newtons?
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One Newton (N) is a force that will accelerate in mass, distance and time.
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What is Hertz?
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Cycles per sound. 20 Hz to 20,000 Hz is the range of human hearing for frequency.
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What is periodic sound?
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Regularly repeating waveform. Components are harmonics of some fundamental frequency and are mathematically related and will have somewhat of a musical quality.
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What is aperiodic sound?
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A waveform that is non-repetitive. Components are not harmonically related. Can have components at all frequencies rather than only multiples of a fundamental frequency. Typically has a “noisy” characteristic or quality.
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Fundamental Frequency:
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a. Partial = In acoustics, it is any single frequency component of a complex tone.
b. Lowest partial in a complex wave. c. Lowest component frequency of a complex wave. |
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What are complex sound waves?
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When two or more sine waves or pure tones are combined, a complex wave occurs. The exact same tones combine in different ways depending on the phase relationships of the component pure tones so that the resultant wave form looks different. The ear is not sensitive to phase and the sound will be the same to the ear. Joseph Fourier noted that any complex sound can be broken down into a series of component pure tones.
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What is phase?
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A particular point of advancement of a cycle usually expressed in degrees of a circle. One complete cycle is 360 degrees.
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What are overtones?
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a. The fundamental frequency is not an overtone.
b. Therefore, the first overtone is the frequency which is two times the fundamental frequency---fo x 2. c. The second overtone is the frequency which is three times the fundamental frequency---fo x 3 d. IF 125 Hz is the fundamental frequency, then 250 Hz would be the first overtone and 375 would be the second overtone, etc, etc. |
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What are harmonics?
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a. Whole number multiples of a fundamental frequency.
b. First harmonic is the fundamental frequency, etc. c. Second harmonic is the frequency which is two times the fundamental frequency---fo x 2. d. Third harmonic is the frequency which si three times the fundamental frequency. |
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What is sound spectrum language?
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Means illustrating the individual components of a whole. It is also a means of demonstrating the occurrence of discrete events or parts of the whole. A line spectrum in sound analysis usually shows discrete frequencies as parts of a larger acoustic event.
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What are simple sound waves?
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Also called “Sine Waves” have three parameters:
a. Amplitude b. Frequency c. Starting phase |
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What is phrase angle notation?
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The phase change in a complete vibratory cycle is 360 degrees. Its phase angle is 90 degrees.
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What are phrase relationships?
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The relationship between two or more vibrations or wave motions.
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What is speed of sound?
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344 M/sec or 1130 ft/sec
a. Dependant on medium density. b. Dependant on medium temperature. |
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What is Noise, the definition of noise:
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Sound with great irregularity in the wave form.
b. Unwanted sound. c. Usually aperiodic sound. |
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What are the different types of noise?
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Pink, White, Speech Spectrum, Narrow Band, and Saw Tooth.
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What can the different types of noise be used for?
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a. Pink: a useful audio sound source for further processing, and also a source of random control voltages for controlling other parts of the synthesizer.
b. White: It is used by some emergency vehicle sirens due to its ability to cut through background noise, which makes it easier to locate c. Speech Spectrum: Good for masking speech. d. Narrow Band: Excellent for masking pure tones. e. Saw Tooth: According to the lecture notes, saw tooth noise is essentially useless for audiometric purposes. |
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What is the formula for finding dB SPL when the ratio of two sounds are given?
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20 xlog Po/Pr
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How does ratio and interval scales relate to dB?
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The very large values of sound intensity are too unwieldy to record so this problem can be solved by converting ratio scales into interval scales.
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What are interval scales and ratio scales?
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a. The very large values of sound intensity are too unwieldy to record so this problem can be solved by converting ratio scales into interval scales. Interval scales are the conventional way, adding a number to each successive number. A ratio scale is when we count by successive multiplication of a numerical unit, if it is apparent that each successive product has twice the numerical value of its predecessor, such a scale is called a ratio scale
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What is O dB SPL?
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Zero (20 µPa RMS-threshold of human hearing) Decibel Sound Pressure Level
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What is dB SPL?
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Decibel Sound Pressure Level.
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