如何为正在使用swift播放的声音添加延迟

import AVFoundation

let engine = AVAudioEngine()
let playerNode = AVAudioPlayerNode()

engine.attach(playerNode)
engine.connect(playerNode, to: engine.mainMixerNode, format: nil)

let audioFileURL = Bundle.main.url(forResource: "sound", withExtension: "mp3")!
let audioFile = try! AVAudioFile(forReading: audioFileURL)
let audioFormat = audioFile.processingFormat
let audioFrameCount = UInt32(audioFile.length)
let audioBuffer = AVAudioPCMBuffer(pcmFormat: audioFormat, frameCapacity: audioFrameCount)!
try! audioFile.read(into: audioBuffer)

let delayNode = AVAudioUnitDelay()
delayNode.delayTime = 0.5 // 设置延迟时间，单位为秒
engine.attach(delayNode)
engine.connect(playerNode, to: delayNode, format: audioFormat)
engine.connect(delayNode, to: engine.mainMixerNode, format: audioFormat)

engine.prepare()
try! engine.start()
playerNode.scheduleBuffer(audioBuffer, at: nil, options: .loops, completionHandler: nil)
playerNode.play()