Audio Basics:Propagation, Amplitude, Frequency and Timbre

SHIM, WooYoung

March 11, 2013

About Presenter and Contents

SHIM, WooYoung

Family Name First Name

� Location: Seoul, Korea

� This lesson is for week 1 of Introduction To Music Production at Coursera.org

� It does a broad overview on some basic properties of sound i.e. propagation, amplitude, frequency and timber

Propagation (1)

Sound can go through a variety of mediums Sound can go through a variety of mediums e.g. air, metal, water.e.g. air, metal, water.

In other words, sound is a sequence of waves of pressure which propagates through compressible media[1]. During propagation, sound goes at a different rate, or a different speed by the characteristics of the medium.

[1] http://www.jhu.edu/virtlab/ray/acoustic.htm

Propagation (2)

If sounds arrive in different time, our brain will If sounds arrive in different time, our brain will recognize it, resulting in a sense of space.recognize it, resulting in a sense of space.

Therefore, it is possible to create a sense of space by manipulating and mixing sounds, and all of them are based on the propagation of sound.

* Sound travels at 340 meters per second in the air, generally.

Amplitude (1)

The wave of sounds in air is longitudinal, and the amount of air compression leads to the amplitude of sounds

In case of longitudinal waves, the

[1] http://www.getting-in.com/guide/a-level-physics-longitudinal-and-transverse-waves

In case of longitudinal waves, the direction of vibration is parallel to the direction of propagation. As a sound propagates, the air repeats compressing and rarefying.

When air is getting more dense, or getting less dense, we hear that as being louder, or quieter. (The higher the amplitude the louder it is.)

[1]

Amplitude (2)

Amplitude is measured in decibels (DB), which is a relative measure.

Context

From zero at the quietest thing, then gets louder until the limit we can

Term Range

DBSPL(sound pressure level) until the limit we can

perceive.(sound pressure level)

DBFS(Full Scale)

From zero at the loudest possible thing, then it goes negative

* When producing music, amplitude is a primary concern because audio mixing is largely based on controlling the amplitude of tracks, making them relative to each other.

Amplitude (3)

Dynamic range is an important factor when looking at gear, e.g. buying a microphone

Dynamic range in a piece of gear is the range levels between the noise

[1]

[1] http://www.analog.com/en/content/relationship_data_word_size_dynamic_range/fca.html

the range levels between the noise floor and the distortion.

* Our own ears also have a dynamic range, the dynamic range of a piece of music means the range from its quietest section to it loudest one.

Frequency and Timber (1)

Frequency is how fast the sound is vibrating. The higher frequency, the higher pitch

[1] http://dpaudioa.blogspot.kr/2011/02/frequency-amplitude-and-eq.html

[1]

* Amplitude and frequency is independent to each other, and there are a variety of ways in that we can have audio effects manipulating only certain parts of sound.

Frequency and Timber (2)

Timbre is the collection of sound in multiple Timbre is the collection of sound in multiple frequencyfrequency

Every instrument has energy at multiple frequencies, and an equalizer (actually a collection of filters) affects the amplitude at specific frequency.

* Generally it is said that the range of human hearing is between 20 Hertz and 20 kilohertz

End of Presentation