ios - Two NSTimers with one governing the activity of the other? -

i've been looking @ thread re: voice detection (http://mobileorchard.com/tutorial-detecting-when-a-user-blows-into-the-mic/).

i'm looking implement similar, however, following variation.

the leveltimer in example fires continuously every .03 seconds. need wrap timer around voice check process runs (say) 10 seconds.

i'm finding having like:

outertimer = [nstimer scheduledtimerwithtimeinterval:10.0                                               target:self                                             selector:@selector(outertimerfinished:)                                             userinfo:nil                                              repeats:no];  leveltimer = [nstimer scheduledtimerwithtimeinterval:0.03                                               target:self                                             selector:@selector(listenforsounds:)                                             userinfo:nil                                              repeats:yes]; 

…where outertimerfinished method calls [leveltimer invalidate] isn't working - maybe due thread blocking?

so can me determine way leveltimer work, specific amount of time?

thanks.

put counter in listenforsounds: method, , increment each time method called. if want run leveltimer 10 seconds say, check when counter > 333 , invalidate timer.