"I've never heard a voice on/in an eleven years old." 

I happened to have heard it said but I didn't know if I heard it correctly.  Is it "in" is called for?  Thanks.

From the dictionary: "In him I see a great leader figure."   That's how I think "in" is correct in this sentence.

Regards,

TN

tinanam0102

“ "I've never heard a voice on/in an eleven years old." ”

I've never heard a voice like that on an eleven-year-old before!

I've never heard such a voice on an eleven-year-old!

What a set o' pipes on that guy! 

tinanam0102

“ When you say "slang, do you mean, in a causal conversation, you'd say "I've never heard such a voice on an eleven-year-old before!"?

And in a written essay, you'd choose "in" because it's more "formal"? ”

But I don't think any US native speaker would be put off by hearing "What a voice on that guy!" 

tinanam0102

“ 1.  What does "Go ahead, I'm a sucker for you!"?  I'm a lollipod for you?  It's a slang right?

It's definitely slang, but I don't attribute its origin to the lollipop (note the spelling).  I could be way off base.

When I refer to someone as "a sucker," I'm thinking in terms of the famous P. T. Barnum quote, "Never give a sucker an even break."  (P. T. Barnum was co-founder of Barnum and Bailey's Circus.)  I believe he also invented the expression, "There's a sucker born every minute."

The expression "A fool and his money are soon parted" also fits in here somewhere.  "Suckers" are people who are easily fooled into spending their money on things which have no value.

If a girl makes a fool out of a guy by allowing him to do whatever she wants, and giving nothing in return; we would say, "He's a sucker for her."

I don't know if this fits the context of your excerpt.

Just as an aside, "slang" is an adjective and an uncountable noun.

So we can say "This is a slang expression."  "This is slang."  "This is an example of slang."  We don't use it as a countable noun:  This is a slang.   These are slangs.

2.  You wrote: "What a set of pipes on him!".  What does that mean?

With due respects to my friend Philip, this is an allusion to Bach's Royal Instrument, the pipe organ, or the church organ.  If you've ever seen a big old church with a big old organ, you've probably seen a set of pipes   -   or as Philip would say, a rank  of pipes   -   yea, several  ranks of pipes.

So in good fun, we refer to the vocal chords of a well-endowed singer as "a set of pipes."

(No, not that  well-endowed!)  .”

tinanam0102

“ 1.  "Go ahead.  I'm a sucker for you" was said by my American customer.  At that time we had differences on price range.  Did he think I decieve him?  Or like bad services our team provided and he wanted to complain a little? 

I'll have to guess.  He thought you were giving him a line of bull   -    that you were trying to overcharge him by making the car seem more valuable than it really was.  You were trying to play him for a sucker.  "Go ahead, I'll play your silly game.  (But I know it's a game, and I'm not really fooled by it.  I'm wise to you.)"

That is, "Okay, I'll be your sucker   -    but not for long."

2.  (No, not that well-endowed!)  --  Is it a sarcastic remark to a person whose singing is average but this person thinks she sings like "Sarah Brightman"?

Your explanation is better than mine.

I meant, "No! Not that  well-endowed, this  well-endowed."

Opera singers have been known through the years for being buxom.  (It ain't over until the fat lady sings, etc.)  "Well-endowed" is sometimes used to describe one's physical attributes. I was referring more to the god-given talent and voice-production equipment.  Careless of me. ”