Tone

Revision as of 22:04, 13 January 2016

This will generate sound at a given frequency for a given length of time in seconds.

Tone( [ float length, float frequency, int samplerate, int channels, string type, float level ] )

float  length = 10.0

Length of time in seconds.

float  frequency = 440

Tone frequency.

int  samplerate = 48000

Audio sample rate.

int  channels = 2

Number of audio channels.

string  type = "Sine"

"Silence", "Sine", "Noise", "Square", "Triangle" or "Sawtooth".

float  level = 1.0

The amplitude of the waveform. Default = 1.0 (or 0dB, the maximum level possible without clipping).

For a particular decibel level, use the equation level = 10 ^{dB / 20}

For example, create a -12dB tone with level = 10^-12/20 or 0.251.

The audio sample type is 32-bit float. Use ConvertAudio if this is not what you want.

Discussion

Tone(frequency=2, samplerate=48000, channels=2, type="sine", level=0.4)

In the figure above, a sinus is generated (on a gray clip with framerate 24 fps). The period of the waveform (in frames) is the framerate divided by frequency (or fps/freq, which is 24/2=12 frames in our example). The part of the graph which is light-green represents all samples of the frame under consideration (which is frame 1 here). The number of samples in a particular frame is given by the samplerate divided by the framerate (which is 48000/24 = 2000 samples in our example).

More generally, the waveform above is described by

g(n,s) = level · sin(2 · pi · (frequency · n / framerate + s · frequency / samplerate))

with n the frame and s the sample under consideration (note that s runs from 0 to samplerate/framerate - 1).

In the example above, this reduces to

g(n,s) = 0.4 · sin(2 · pi · (2 · n / 24 + s · 2 / 48000))

with n the frame and s the sample under consideration (note that s runs from 0 to 1999).

Note that the bars are made with Histogram and the graph with the AudioGraph plugin.

Examples

We Wish You a Merry Christmas, in harmony (author hanzfrunz)

Changes