I mean a dot (.)
but maybe I found a solution also fot char ',' :
NSString *text = @"Line one. LineTwo aftre a pause. Line three, pause here again.";
text = [text stringByReplacingOccurrencesOfString:@"," withString:@"."];
NSArray *a = [text componentsSeparatedByString:@"."];
for(NSString *line in a)
{
AVSpeechUtterance *utterance = [[AVSpeechUtterance alloc] initWithString:line];
utterance.voice = [AVSpeechSynthesisVoice voiceWithLanguage:[self.defaults objectForKey:LINGUA]];
utterance.rate = 0.28;
utterance.**postUtteranceDelay** = 0.3;
[self.synthesizer speakUtterance:utterance];
}