Just recently, probably since the latest Firefox update, if I am listening to an audio stream in Youtube, opening a new tab may interrupt the audio briefly. This is new, and did not occur in previous editions. Opening a blank tab does not interrupt the audio. If a tab is opened by a website (referral or by selecting a favorite) it may not interrupt the audio. Opening an eBay page always interrupts the audio (two short interruptions and then the audio continues.) This support page to enter a detailed question caused the audio to be interrupted. Opening one Gmail ID page from another Gmail ID page will interrupt the audio.