- Set them off, yourself. There's a difference when you know it's going to be happening... It creates a level of control & expectation.
- Acclimate with similar sounds. Pop your own popcorn, bounce balls (carry a blue racket ball, play basketball, etc.), buy a pair of drumsticks & learn beats, practice your pool/billiards break, learn Morse Code, etc.
- Learn to distinguish sounds. At one point in my life I could tell the difference between different manufacturers of the same caliber of weapon... Under ideal conditions. Not always. But absolutely for AK v M16 v SAW v 240golf v .38 v 9mm v .40 v .45 v et cetera. The difference between those & fireworks? Pfft. Forgetaboutit! Cake. Even if a dryer lid slamming down,p could spin me up & out. LOL. But listening for the boom? Intellectualizing it changes things :D I've also gone around listening for the difference between banging screen doors, solid wooden doors, hollow wooden doors, dryers, you name it. Differentiating the sounds of different fireworks? Fun fun. Also pretty. Although I'll often do it with my eyes shut, just to test myself. Expectation is a part of this, as well.
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Alternatively? Go camping back of beyond. Take a long train ride or airplane ride (ambient noise + being 30-40,000 feet -or hundreds of miles- away nixes the likelihood of even a shizzer of sparks much less here comes the boom! ). Sailing/Boating trip. Scuba Diving. Sound Proofed Hotel Rooms. Music Studios. Concerts/Clubbing (drowns out the noise in sensory overload). Go shooting. Medicate & sleep through.