Steps

Create a Twilio Account

Create a Twilio account and purchase a new number.

Choose your Filter

There is a TODO in the twilioSocket.ts file with the filter options. Select which one you want from the list:

• highPassFilterAndSaveToWav
• bandPassFilterAndSaveToWav
• biquadBandPassFilterAndSaveToWav

Run the Server

Use the VS Code "Run Server" task or the following command to run the server:

npm run dev

This will print out an ngrok URL. Copy that.

Paste the Ngrok URL into Twilio

In Twilio, navigate to your phone number and paste the ngrok URL into the URL field:

Test it Out

You can use https://mynoise.net/ to generate background noise for testing. Once the noise generator is playing, call your Twilio number and say a few things. Hang up.

When the websocket disconnects, the server will create two files: twilio_call_filtered.wav and twilio_call_unfiltered.wav.

Visualize the Filter

Open the wav_visualizer.ipynb notebook and run the code cell.

Example:

Twilio Resources

Start Payload

{
    event: 'start',
    sequenceNumber: '1',
    start: {
      accountSid: '1234',
      streamSid: 'MZ14f465fb39b99eb0b0efd4bd5456cc8d',
      callSid: '6789',
      tracks: [ 'inbound' ],
      mediaFormat: { encoding: 'audio/x-mulaw', sampleRate: 8000, channels: 1 },
      customParameters: { from: '+13152716606' }
    },
    streamSid: 'MZ14f465fb39b99eb0b0efd4bd5456cc8d'
}

Media Payload

{
"event":"media",
"sequenceNumber":"3122",
"media":
  {
    "track":"inbound",
    "chunk":"3121",
    "timestamp":"62411",
    "payload":"////f39////////..."
  },
"streamSid":"MZe36496a19c2240a634016c64787ee984"
}