Failed to construct 'AudioContext': number of hardware contexts reached maximum

You should really only have one AudioContext in the page.

From the docs: "In most use cases, only a single AudioContext is used per document."

I can't really think of a reason why you'd ever need more than one. Is there a specific issue you've run into that caused you to create multiple contexts?

AudioContext.close() will release the hardware of the context, but check that it is available only for recent versions of chrome and firefox. Not available for IE aparently. Check the documentation: https://developer.mozilla.org/en-US/docs/Web/API/AudioContext/close