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# Coursera Introduction to Music Production: Basic Properties of Sound

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## Melissa Mery

on 19 August 2013

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#### Transcript of Coursera Introduction to Music Production: Basic Properties of Sound

Introduction to Music Production:Basic Properties of Sound
Hey Hey!
Hey! My name is Mel, 19. Colombian House, progressive and tech House Dj

What is sound?
Propagation
The sound can actually propagates faster in water than in air.
Conclusion
Frequency, amplitude and propagation are independent properties of sound. Manipulating them can produce sound effects.
We should talk about carefully about decibels, it would depend of the context.
Hertz is the unit of measure of frequency
The propagation of the sound through different mediums will be different. It would depend on the medium and other factors like humidity, temperature and elevation
And today we're gonna learn about some Basic properties of Sound
Lesson 1:Basic Properties of Sound
Amplitude, Propagation, Frequency and Timbre
The pressure variations in the air, which propagates through different mediums
.

The rate/speed of sound
Can be affected/changed by some properties of air like: the elevation, temperature, humidity,
Speed of sound at sea level travels at...
340 meters per second.
1 mile in 5 seconds
1 foot per millisecond
1 kilometer in 3 seconds

What is Amplitude?
Amplitude is "the kind of extent of the wave, how wide it's moving or actually, how much the air compresses and rarifies as that wave form moves or propagates through the air" Loundon Stearns
Types of Waves
The types of waves depends of the medium the air moves through.
Longitudinal wave
: the propagation will have the same parallel direction of the wave.
i.e sound in air
Transverse wave
: the direction of the vibration is perpendicular to the direction of the propagation. i.e
air on a pond.
How do we measure the Amplitude?

Amplitude is measured in Decibels. And because of its relativity it must be used carefully.
It is a relative measure because dB do not have a definite set point where zero

Decibels: DBSPL and DBFS

DBSPL:decibels of sound pressure level. Is use when when we are talking about air and the the threshold of hearing, or the quietest thing we can possibly hear.
SPL: sets where's the zero.
Zero: quiets thing you can hear
DBFS or Full Scale
Is use in the digital domain: the computer -> DAW
Zero = the loudest thing you can hear

Where
And then the negatives numbers represented on the computer will express lower levels of sound.
Amplitude vs Loudness
Amplitude: measurable by a computer
loudness: is our/human perception of amplitude
The propagation of the sound and it speed depends of the medium the sound is moving through. Some of the mediums are: air, liquids(i.e water), solids (metal, wood)
Sound effects related with Propagation and the mediums the sound moves through
Flanger
Reverb, phasers
Delay
Sounds effects
related with Amplitude
Expanders
Gates
Compressors
,Limiters
Frequency is
How often a wave repeats within a fixed amount of time, how fast the sound is vibrating.
Frequency and Amplitude vs Pitch and Loudness
Frequency and Amplitude: measured by a computer
Pitch and Loudness: perceived by the human being
High and Low frequency
A
high frequency
wave would have lots of these moving very quickly in a certain time. The period is smaller than in the low frequency type.
Low frequency
: waves would have less of these moving through a certain time, the period is bigger.
Frequency and Amplitude
They are not correlated to the propagation rate. Then, all of
them are completely independent
We can have a low low amplitude with a
high frequency and vice versa.
Hertz Frequency and range of human hearing
Hertz is the unit of measurement used to measure the frequency.
1 Hertz(Hz):once per second, 1Hz vibration per second.
Human hearing
Lowest frequency we can hear: 20 Hz
Highest frequency is : 20,000 Hz/20 kilohertz.
A human being
rarely can we hear 20,000 hertz, that's we say that the upper end of hearing is around 18000 Hz or 18 kilohertz
20.000 to 180.000 Hz
And finally...Timbre!
Timbre is the collection of sound in multiple frequencies. Timbre help us to distinguish
different instruments with the same pitch, loudness and duration/length of the wave.
.
.
Since the timbre is hard to distinguish, we use a spectrum analyzer to see how the sound actually is energy at multiple frequencies. This tool is also helpful to see how amplitude and frequency change over time
Thanks for watching!
Wait for the next assignment... next week!
Hope you enjoyed it
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