{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Exploring Beat Frequencies using the `Audio` Object"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "This example uses the `Audio` object and Matplotlib to explore the phenomenon of beat frequencies."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "%matplotlib inline\n",
    "import matplotlib.pyplot as plt\n",
    "import numpy as np"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "from IPython.html.widgets import interactive\n",
    "from IPython.display import Audio, display\n",
    "import numpy as np"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "def beat_freq(f1=220.0, f2=224.0):\n",
    "    max_time = 3\n",
    "    rate = 8000\n",
    "    times = np.linspace(0,max_time,rate*max_time)\n",
    "    signal = np.sin(2*np.pi*f1*times) + np.sin(2*np.pi*f2*times)\n",
    "    print(f1, f2, abs(f1-f2))\n",
    "    display(Audio(data=signal, rate=rate))\n",
    "    return signal"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "v = interactive(beat_freq, f1=(200.0,300.0), f2=(200.0,300.0))\n",
    "display(v)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "v.kwargs"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "f1, f2 = v.children\n",
    "f1.value = 255\n",
    "f2.value = 260\n",
    "plt.plot(v.result[0:6000])"
   ]
  }
 ],
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