How to play a sound from a socket.io event?

I want to play a sound file on the client side whenever the space bar is pushed.

The client side successfully emits the 'bang' event when the space bar is pressed:

$(window).keydown(function(event){
    alert(event.keyCode);
if (event.keyCode == 32){
        socket.emit('bang'); 
}
});

The server side succesfully prints "bang" in the control.log so hopefully it is also emitting 'play':

io.on('connection', function(socket){
  socket.on('bang', function(){
    console.log('bang');
    io.emit('play');
  });
});

However, back on the client side to play the sound, nothing is happening. The code I am using is:

var sound = new Audio('/public/audio/1.mp3');   

socket.on('play', function () {
    sound.play();   
});

Do I need to include something in the body to do with audio or a in order to use the Audio object.

I have searched this quite thoroughly but I am very new to node.js, html and socket.io. I tried the advice given here: Play Audio from client when message is recieved from socket.io - node.js

But when I put in:

app.use('/public', express.static('/path/to/public'));

'static' became flagged and upon trying to run the code I recieved an error message: 'express is not defined, even though I put it before:

app.get('/', function(req, res){
  res.sendFile(__dirname + '/index.html');
});

as advised in that post. I also tried it after and got the same error.

Please help me.