Does a person without bottom teeth sound funny or difficult to understand, especially on the phone?

Maybe yes, maybe no: Everyone speaks differently, with or without teeth. Can't say for sure since it is up to the individual.

Change in speech: The way you talk and sound can change when someone is missing teeth. Replacing the teeth with fixed or removable restorations can help restore the way a person talks.

Hard to say: Often people can adapt quite well to changes in their oral "architecture" so you may or may not hear a decernable sound difference, with or without teeth.

Perhaps: While missing all your bottom teeth may or may not be the only reason why you sense some alteration in speech, or whether or not it is noticeable to others, it certainly does affect one's speech. Even having crooked natural teeth can have slight effects on speech patterns. I recommend that you see a dentist to discuss replacement of your teeth, not only for speech, but digestion and self esteem.

Could be -: It all depends on how long they have been edentulous and how well they have adapted to it, also how long they have been edentulous ... Hope this helps.