Well, the only way to avoid those is to have your phone in a safe distance from the aforementioned speakers.
In any case, you will get such static with any cell phone, as when a cell phone emits, it needs to broadcast with quite a powerful emission in order to reach the nearest BTS
(Base Transceiver Station), which can be a few kilometers away if you're not in a city, and several buildings away if you are in a city.
Hence the equation : powerful radiowaves at a frequency that interferes with ordinary speakers -> no need to change your phone, you'll get them anyway.
So really, the only way to avoid that is to put your phone at least one meter from the 'annoyed speaker', it usually does the trick.
On the other hand, you usually get those static when your phone is about to ring (it starts to emit to communicate with the BTS
when an incoming call arrives), so you can also use that as a 'pre-ring'
(then again, your phone will emit also on a 'random' schedule, just to confirm with the network that it is still alive and registered. Then you'll get an the static noise for a couple of seconds, but no more)
707, former cellphone manufacturer