where t is the time, and f the frequency of the oscillation. Sound on a computer is a sequence of numbers and in this post we will see how to generate a musical tone with numpy and how to write it to a file wav file. Each musical note vibrates at a particular frequency and the following script contains a function to generate a note (tone(...)), we'll use this function to generate the A tone creating an oscillation with f = 440 Hz.
from scipy.io.wavfile import write from numpy import linspace,sin,pi,int16 from pylab import plot,show,axis # tone synthesis def note(freq, len, amp=1, rate=44100): t = linspace(0,len,len*rate) data = sin(2*pi*freq*t)*amp return data.astype(int16) # two byte integers # A tone, 2 seconds, 44100 samples per second tone = note(440,2,amp=10000) write('440hzAtone.wav',44100,tone) # writing the sound to a file plot(linspace(0,2,2*44100),tone) axis([0,0.4,15000,-15000]) show()Now we can play the file 440hzAtone.wav with an external player. This plot shows a part of the signal generated by the script:
previous post we can verify that 440 Hz is the fundamental frequency of the tone.