8_Beat-Frequencies.py

# coding: utf-8

# # Exploring Beat Frequencies
# 
# This simple code will let us play with close frequencies and hear the beatings created by intermodulation. It's also a great example of the interactivity we can achieve with Jupyter Notebook.

# standard bookkeeping
get_ipython().magic('matplotlib inline')
import matplotlib.pyplot as plt
import numpy as np
from IPython.display import Audio, display

# interactivity here:
from ipywidgets import interact, interactive, fixed, interact_manual
import ipywidgets as widgets


# In[5]:


plt.rcParams["figure.figsize"] = (14,4)


# Let's define a simple fuction that generates, plots and plays two sinusoids at the given frequencies:

# In[6]:


def beat_freq(f1=220.0, f2=224.0):
    # the clock of the system
    LEN = 4 # seconds
    Fs = 8000.0
    n = np.arange(0, int(LEN * Fs))
    s = np.cos(2*np.pi * f1/Fs * n) + np.cos(2*np.pi * f2/Fs * n)
    # start from the first null of the beating frequency
    K = int(Fs / (2 * abs(f2-f1)))
    s = s[K:]
    # play the sound
    display(Audio(data=s, rate=Fs))
    # display one second of audio
    plt.plot(s[0:int(Fs)])