Playing sound in swift 4. Source: https://stackoverflow.com/questions/32036146/how-to-play-a-sound-using-swift/32036291#32036291

playSound.swift

import AVFoundation
    
    var audioPlayer: AVAudioPlayer!

    let soundURL = Bundle.main.url(forResource: "soundName", withExtension: "soundFormat")

    do {
        audioPlayer = try AVAudioPlayer(contentsOf: soundURL!)
    } catch {
        print(error)
    }

    audioPlayer.play()

playSoundV2.swift

import AVFoundation

var player: AVAudioPlayer?

func playSound() {
    guard let url = Bundle.main.url(forResource: "soundName", withExtension: "mp3") else { return }

    do {
        try AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayback)
        try AVAudioSession.sharedInstance().setActive(true)



        /* The following line is required for the player to work on iOS 11. Change the file type accordingly*/
        player = try AVAudioPlayer(contentsOf: url, fileTypeHint: AVFileType.mp3.rawValue)

        /* iOS 10 and earlier require the following line:
        player = try AVAudioPlayer(contentsOf: url, fileTypeHint: AVFileTypeMPEGLayer3) */

        guard let player = player else { return }

        player.play()

    } catch let error {
        print(error.localizedDescription)
    }
}