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Properties of Sound

1st. Week's Assignment for Coursera's Introduction to Music Production, by Loudon Stearns

David Sanchez

on 11 March 2013

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Transcript of Properties of Sound

What is Sound Sound is a form of energy, Kinetic energy.

Sound is produced when changes in air pressure, caused by the vibration of molecules create waves, sound waves.

When sound waves reach the ear, its internal configuration converts the changes of air pressure in to electrical impulses that the brain interpret as SOUND Amplitude Properties of Sound Is the amount of energy that the sound wave carries
Amplitude is the degree of compression and rarefaction of particles in a soundwave
Determines the extent of the oscilating displacement of each particle affected by a disturbance in a medium. Frequency Timbre Timbre is a concept that is co-related to Frequency and Amplitude Propagation Propagation is related to how a sound wave travels through a medium There are two scales for measuring sound in Decibels:
dBSPL (Sound Pressure Level); is used for meassuring sound in the air
dBFS (Full Scale); used for meassuring sound in binary language. Amplitude vs. Loudness Is how fast the air is vibrating given an air disturbance
Frequency meassures how many times a particle goes back and forward in a given time unit Frequency is meassured in Hertz (Hz)
A frequency of 1Hz means that an event takes place once per second. Credits http://askthephysicist.com/ask_phys_q&a_old5.html
http://blog.educastur.es/iscm/category/apuntes/page/3/ The medium can be Liquid Solid Gas Air Metal
Wood Water Speed of sound will be affected by the nature and properties of the medium in which it travels

The main two properties of a medium that affect sound waves are:
Density Temperature and density and humidity of air varies depending on geographic location (Lat, Long, Altitude) How does temperature affect propagation of sound waves? "Heat, like sound, is a form of kinetic energy. Molecules at higher temperatures have more energy, thus they can vibrate faster. Since the molecules vibrate faster, sound waves can travel more quickly" (1) 1) http://www.ndt-ed.org/EducationResources/HighSchool/Sound/tempandspeed.htm
2) http://www.ndt-ed.org/EducationResources/HighSchool/Sound/speedinmaterials.htm How does density affect propagation of sound waves? ...the more dense substance must have more mass per volume. More molecules are squeezed into the same volume, therefore, the molecules are closer together and their bonds are stronger. Since sound is more easily transmitted between particles with strong bonds, sound travels faster through denser air. (2) Propagation has a mayor role in sound Spacialization Spacialization is the process in which the brain can locate the source of a sound as the characteristics of the space where it travels. Our brain has an impressivelly accurate capacity of determining the location and distance of a sound by decoding certain elements: The AMPLITUDE of a sound wave is related to how LOUD we perceive it. AMPLITUDE LOUDNESS Meassurement Perception Not all Frequencies sound equally loud at a same Amplitude High Frequencies are perceived as louder than lower frequencies, so High Pitch notes need less energy to be perceived as loud as a low pitch note Timbre it's like the tone of a sound, is a collection of frequencies that gives certain color to a sound Sounds in nature are complex
Each sound is composed by numerous frequencies, although we perceive it like one
Timbre depends on the quantity of harmonics and the amplitude of each one Timbre depends of the materials and components of the source of a sound, Timbre allows us to tell the difference between two instruments playing the same note at the same scale. In sound synthesis, the only sound wave that has no timbre is the sine wave.

Sine waves have a fundamental tone with no overtones

Other waves, like Sawtooth waves have a fundamental Freq. and n Tones at specific amlutudes. Sine Saw Reccomended links http://askthephysicist.com/ask_phys_q&a_old5.html
http://www.acs.psu.edu/drussell/Demos/waves/wavemotion.html The Human ear can roughly hear between 20Hz and 20KHz This range can vary depending on a subjects age, gender or "sound culture" Time-lagg: the difference of time in which sound reaches one ear end then the other
Reflection: How sound reflects from one surface to another and in to our ears
Reberberation: Is the persistence of sound caused by the collection of all reflections of sound in a space since the origin of the sound to its total disipation. Sound will travel faster in hot weather
Sound travels slower in high altitude with low temperature Amplitude is measured in Decibels (dB), Db is a logarithmic unit of meassure. Articulation Articulation, also known as envelope, is the way a sound evolves through time This property, as Timbre, help us tell from one instrument from another The way in which the sound of a VIOLIN (played with a bow) articulates is slow at the beginning, and it sustains for a period of time, while the sound of a PIANO is strong at the beginning and lowers its levels quicker. In sound synthesis, we create this effect using envelope generator. In acoustic instruments, the Amplitude of sound varies trough time, This is what we refer to a the Envelope of a sound An envelope generator is more commonly called an ADSR envelope A: Attack
D: Decay
S: Sustain
R: Release In an AC Voltage sound carrier, the ADSR envelope is connected to the VCA (Voltage Controled Amplifier)
The envelope functions at DC and
An ADSR envelope is an Amplitude modulator. Images Thank's for wathcing! I'm David Sánchez, from Venezuela and for this week's assignment I chose the topic "Sound Basics", I really hope it has usefull information and that you all enjoy it...... Let's begin Hello! Press Play to watch video
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