MediaStreamTrack's onmute event handler is called when the mute event is received. 
Such an event is sent when the track is temporarily not able to send data.
track.onmute = muteHandler;
 A function to serve as an event handler for the mute event. The event handler function receives a single parameter: the event object, which is a simple Event object. 
 In this example, an onmute handler is established to set the content HTML of an element to display the "muted speaker" Emoji. 
myTrack.onmute = function(evt) { playStateIcon.innerHTML = "F507;"; };
| Specification | 
|---|
| Media Capture and Streams  # dom-mediastreamtrack-onmute  | 
| Desktop | Mobile | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | WebView Android | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | |
onmute | 
26  | 
12  | 
59  | 
No  | 
15  | 
11  | 
≤37  | 
26  | 
59  | 
14  | 
11  | 
1.5  | 
mute event and its type, Event.MediaStreamTrack.muted to determine if a track is currently mutedMediaStreamTrack.onunmute, the event handler for the unmute event. 
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    https://developer.mozilla.org/en-US/docs/Web/API/MediaStreamTrack/onmute