getUserMedia don't work with AudioContext.createScriptProcessor

I updated my iphone to ios11 beta4,

I trying to record voice and process it, it work with getUserMedia, and the AudioStream can be get. demo: https://webrtc.github.io/samples/src/content/getusermedia/audio/

but when using with AudioContext:

let ctx = new window.webkitAudioContext;
let source = ctx.createMediaStreamSource(stream);
let processor = ctx.createScriptProcessor(1024, 1, 1);

processor.onaudioprocess = function(e) {
     console.log('do something');
}

the audioprocess event can't be triggered. demo:

https://webrtc.github.io/samples/src/content/getusermedia/volume/