I don't have any US developer friends to test this with, but realised I do know a whole community of helpful ones. :)
So my question is - do US iPhones have the British voice for AVSpeechSynthesizer, or does it play a monotone-sounding drone like the simulator does?
Here's the code to test this out:
#import <AVFoundation/AVFoundation.h>
AVSpeechSynthesizer *synthesizer = [[AVSpeechSynthesizer alloc] init];
AVSpeechUtterance *speechUtterance = [AVSpeechUtterance speechUtteranceWithString:@"This is something really special that a speech system could read out. You might find that I'm talking with quite an intelligent english accent. I hope I don't just sound robotic."];
speechUtterance.voice = [AVSpeechSynthesisVoice voiceWithLanguage:@"en-gb"];
speechUtterance.rate = 0.20;
[synthesizer speakUtterance:speechUtterance];
On one hand it makes sense that it would ship with support for all languages. On the other hand, I know how big text-to-speech voices can be, so it'd also make sense to only include the native language, and in the US that may not include the UK voice.
From my own tests, changing the language to something such as @"en-au" (for Australia) sounds good too on my device.
Tried it with 3 voiceWithLanguage settings on an iPad mini:
en-gb -> male voice with an English accent
en-au -> female voice with Australian accent
en-us -> female voice with no accent (OK - with an American accent ;-)
Same results on a 5th generation iPod touch.