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by: Alex Ellzey

8

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3

# Sound EI 300

Alex Ellzey
USM

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Sound notes from week 2-4
COURSE
Intro to Audio Production
PROF.
Jeff Rassier
TYPE
Bundle
PAGES
3
WORDS
CONCEPTS
Sound, Audio, production, MCJ
KARMA
75 ?

## Popular in Journalism and Mass Communications

This 3 page Bundle was uploaded by Alex Ellzey on Wednesday September 21, 2016. The Bundle belongs to EI 300 at University of Southern Mississippi taught by Jeff Rassier in Fall 2016. Since its upload, it has received 8 views. For similar materials see Intro to Audio Production in Journalism and Mass Communications at University of Southern Mississippi.

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Date Created: 09/21/16
Sound  Soundwave: periodic waves in atmospheric pressure o A sound radiates spherically in 3-dimensions and doesn’t go in one direction  Waveform: a graph of a signal’s Sound Pressure Level  Characteristics of waveforms o Amplitude o Frequency o Velocity o Wavelength o Phase o Harmonic content o Envelope  Amplitude distance above & below the centerline of a waveform o normal human ears hears 20-20,000Hz o peak amplitude value- greatest distance between highest positive & negative values of a signal o root mean square- an average of the values of a waveform  Frequency: rate at which a positive and negative amplitude value repeats (represents pitch) o Cycle: one complete positive & negative value o Hertz (Hz): number of cycles per second o Kilo-hertz: thousands of cycles per second  Wavelength: distance of one cycle of a waveform or soundwave (length of the wave) o A 20 Hz cycle would be about 576 ft long o 200 Hz would be 67.5 inches o 2 KHz would be 6.75 inches o 20 KHz would be .0675 inches  Velocity: speed at which a wave travels o Affected by temperature o Sound travels 1.1 foot/second with each rise of 1 degree Fahrenheit o Speed of sound is approx. 1130 ft per second Reflection of sound- sound reflects off a same (though opposite) angle that it hits the surface Diffraction of sound- soundwaves can travel around & through objects  Phase: a degree to which the features of one wave coincides with another wave in time o Sine waves that share the same features are in phase o When a combination of two waves create an increase in amplitude is constructive interference Phase shift: a waveforms lead or lag in time with respect to one another  Harmonic content: presence of several different frequencies within a complex soundwave, in addition to its fundamental note o Partials- frequencies that are present other than the fundamental sound  an A4 on the piano produce a fundamental 440 Hz overtones are the whole number multiples. 880 Hz would be the second harmonic  they occur in multiples of even numbers known as even order harmonics  Timbre: harmonics & relative intensities produces by an instrument or sound source o Tonal balance o Instruments (similar or different) produce harmonics at different amplitudes o Frequency response of every item in the sound chain can change the sonic characteristics of the instrument  Even something as simple as microphone placement can have a major role in the timbre recording 2  Frequency response: range of frequencies & their amplitudes that a system or unit can output relative to the input  Envelope: changes in level that occur overtime during a note or sound o Attack: time it takes sound to reach full amplitude o Decay: how fast the sound levels off o Sustain: how long sound continues after the attack o Release: how long sound remains after sound  Loudness: amplitude of sound (refers to perceived level of sound)  Sound Pressure Level (SPL): amount of pressure in a given area of atmosphere caused by sound o Usually measured in pascals (Pa) o Also expressed in decibels (dB)- 1 Pa = 94 dB  Decibel (dB): unit of audio measurement of SPL, signal level & changes/differences in signal level o dBm: decibels referenced to 1 milliwatt (measurement of power) o dBV: decibels referenced to 1 volt o dB(A), dB(B), dB(C): refers to weighing filters used to account for the nature of human hearing  Changes in levels o A 10 dBm SPL = twice loudness o 6 dBy increase in voltage = twice level o 3 dBm increase in power = twice level  Volume unit meter: audio signal level measure device that usually displays an average of the signal strengths o Electrically 0 dB= +dBm or 1.228 volts  Peak program meter: audio signal level measuring devices with a faster rise time  Psychoacoustics: study of how brain interprets sound 3

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