# Audio Signal Processing

## What is audio signal processing?

- Applications: storage, data compression, effects and transformations, synthesis, description.
- Intentional alteration of sound

## Some basic mathematics

### Sinusoidal functions (正弦函数)

`x [n]=Acos(ωnT +ϕ)=Acos(2 π f nT +ϕ)`

- A:amplitude (振幅)
- ω: angular frequency in radians/seconds
- f =ω/2 π:frequency in Hertz (cycles/seconds)
- ϕ:initial phase in radians
- n: time index
- T =1/ fs:sampling period in seconds(t=nT =n/ fs)