1. 要想在拖动进度条时播放声音，需要使用AVPlayer的addPeriodicTimeObserver方法定期检查当前的播放进度，然后根据需要进行声音处理。

var timeObserverToken: Any?
let player = AVPlayer()

// Add time observer to track the progress of the player
timeObserverToken = player.addPeriodicTimeObserver(forInterval: CMTime(seconds: 1, preferredTimescale: CMTimeScale(NSEC_PER_SEC)), queue: DispatchQueue.main) { [weak self] time in
    guard let self = self else { return }
    if self.player.rate > 0 {
        // If the player is currently playing
        if let currentItem = self.player.currentItem {
            // Calculate the current playback progress in percentage
            let currentPlaybackTime = currentItem.currentTime().seconds
            let totalDuration = currentItem.duration.seconds
            let progressPercentage = currentPlaybackTime / totalDuration
            
            // Play sound based on the current progress percentage
            if progressPercentage > 0.5 {
                // Play sound if the playback progress is more than 50%
                // Add your own sound file here
                self.playSound(soundFile: "sound.mp3")
            }
        }
    }
}

2. 使用扩展实现播放声音的功能。

extension AVPlayer {

    func playSound(on interval: TimeInterval, file: String) -> NSUUID? {
        let interval = CMTimeMakeWithSeconds(interval, preferredTimescale: 600)
        return addPeriodicTimeObserver(forInterval: interval, queue: nil, using: { (time) in
            let trackTime = self.currentItem?.currentTime().seconds ?? 0
            let trackDuration = self.currentItem?.duration.seconds ?? 0
            let progress = trackTime / trackDuration
            
            if progress > 0.5 {
                // Add your own sound file here
                let url = Bundle.main.url(forResource: file, withExtension: "mp3")!
                let audioPlayer = try! AVAudioPlayer(contentsOf: url)
                audioPlayer.prepareToPlay()
                audioPlayer.play()
                
                // Remove observer after playing the sound
                self.remove