Synthesized sound (AudioContext) works a bit differently from playing videos/sound files in the web permissions model, for whatever reason. IIRC Chrome and Fire

Synthesized sound (AudioContext) works a bit differently from playing videos/sound files in the web permissions model, for whatever reason. IIRC Chrome and Firefox both treat various forms of interaction as an OK to synthesize audio, so your browser probably decided you had met that criteria. Chrome has a list of special websites that are given that access automatically, though I doubt this website is on that list...