Re: Speech Jammer ?
Real but not very practical...
Slap on that time frame to cause stuttering needs to be 100mSec plus, so not from nearby reflections.
I recall a dealer meeting in a huge hotel ballroom in Anaheim (probably a couple ballrooms opened up to make one large room) where there was a slap off the back wall in the right time range to mess up speaking.
Indeed, singing is different. Recall how artist Mel Tillis can sing fluently but can't talk without stuttering (it is not an act). Speech is more percussive with sudden starts and stops. Singing is more held notes, so a delayed repeat of a note start is masked by the held note.
It differs from person to person (like stuttering), and I haven't experienced long telephone delays in several decades.
I know this is real, I sold a delay device back in the '80s used for speech therapy (with mic, headphones, and up to 300mSec of delay. A stutterer can practice speaking fluently with DAF (Delayed Auditory Feedabck). They begin with long delay, and gradually reduce it to no delay.
This doesn't have much practical application for music, but for talking heads like on TV, you could really mess up the talent by adding a delayed version of themselves in their earpiece. 
To shut up talkers in a crowd, you would end up making a lot of noise too...
I recall a similar idea, when I had a problem with noisy frogs around a pond, making a racket. I wanted to record the frog call, pitch shift it lower so it sounded like a much bigger frog and play it back twice as loud... Never got around to trying that but i bet it would mess with the frogs tiny little minds.
JR
