Make UIWebView play sound when visit a web game url

Project Description:
Need a solution that can make UIWebView on iPhone play sound when visit this game URL: http://ddninja.flyapps.me

Both Safari and Chrome on iPhone can play the backend sound when visit this webpage. However, when use UIWebView to visit it, there is no backend sound. There must be some special setting to make it work.

Tried many online solutions, such as, but still not working

[[AVAudioSession sharedInstance] setDelegate:self];
[[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback error:nil];
[[AVAudioSession sharedInstance] setActive: YES error: nil];


_webView.allowsInlineMediaPlayback = YES;
_webView.mediaPlaybackRequiresUserAction = NO;