I think you can feel them opening up better than hearing them.

I got a tire valve stem and carved the rubber till it fit into the rubber
hose of the injector. I then filled the injector hose with FI cleaner.
Inserted the valve stem and clamped it.My bomb was now ready.

I used an old FI electrical connector for the fuel injector to insure a
good spark free electrical connecton(This is  a lie-I had gas all over
me). I hooked up the 12V and then pumped the bicycle pump.  You could see
the spray pattern get better and better in one stroke of the pump. 1
infusion of cleaner was all it took, but 3 gave it insurance.

Besides cleaning the injector,I can say that pure concentrated fuel
injector cleaner needs more than an erant spark to ignite it.The place was
a mess with  spilled cleaner.Be careful.I had a running garden hose right
next to me when I did this.