Basic features of sound wave

Sound

Sound is something that is caused by a vibrating object.

A vibrating object causes nearby molecules to vibrate either, and they (normaly) change the air pressure.

It is a type of mechanical waves, which can be represented as

 

y = sin(2 * pi * f *t - k)

 

The important thing is that every audial features such as intensity, timbre ... can be obtained by this equation. Every information is compressed in this equation

 

Pitch

Pitch is a perceptual physical quantity that represents the degree of highness or lowness of a sound.

When we hear sound, we perceive a highness of a sound in a logarithmic way.

 

Frequency and pitch can be transformed to each other according to the equation above.

 

Cents

A semitone can be divided into 100 cents.

In other words, an octave consists of 1200 cents.

 

Sound Power

As we learned in high school, the physical quantity called power is referred to energy per unit time.

In essense, sound power is the energy per time caused by the oscillation of the medium.

*Interesting fact: the sound of an orchestra or a thunder has a sound power of 1W!

 

Sound Intensity

Sound intensity is a sound power per unit space(W/m^2).

Note) Threshold of hearing: 10^(-12) W/m^2 , Threshold of pain: 10 W/m^2

Using TOH, we measure sound intensity using dB

Linear Power to dBm and Vice-Versa - arimas

Loudness

The analogy between frequency and pitch is similar with that of sound intensity and loudness.

It is a subjective perception of sound intensity.

The loudness is determined by the sound intensity and the duration.

 

Timbre

I believe this concept is the most difficult musical feature to define.

Timbre is what makes two sounds different when they have the same intensity, frequency, and duration.

It is fascinating that the distribution of the energy across the different partials make timbre different