In our computer room we have a TV but you can't hear it with headphones on. With a Raspberry Pi and a Griffin iMic USB audio adapter I'm able to capture stereo audio and stream it into Discord.

Capture and stream the audio with mic and discord.js

const mic = require('mic');
const Discord = require('discord.js');

const config = {
  mic: {
    rate: 48000,
    channels: 2,
    device: "plughw:CARD=system,DEV=0"
  },
  discord: {
    token: "<bot-token>",
    guild: "<server-name>",
    channel: "<channel-name>"
  }
}

const client = new Discord.Client();
client.login(config.discord.token)
.catch( () => {
  console.log('Unable to log in with provided token.');
  process.exit();
});

// Start audio capture
let micInstance = mic(config.mic);
let audioStream = micInstance.getAudioStream();

client.on('ready', () => {
  // Filter channels down to voice channels in the guild
  let channels = client.channels.filter( channel => {
    return channel.guild.name === config.discord.guild && channel.type === 'voice';
  });

  // Find channel by name
  let channel = channels.find('name', config.discord.channel);

  if(!channel) {
    console.log(`Unable to find voice channel ${config.discord.channel} in ${config.discord.guild}`);
    process.exit();
  }

  // Connect to the channel
  channel.join()
  .then( connection => {
    console.log('Connected...');

    // Start the audio stream
    connection.playConvertedStream( audioStream );
    micInstance.start();
  })
  .catch( error => {
    console.log('Unable to connect to the voice channel', error);
    process.exit();
  });
});