Why don't Vietnamese understand Vietnamese spoken by a foreigner?

Because of there not enough smarter than your, That's why Vietnamese cannot guess.

It could be any of several reasons: your foreign accent; incorrect pronunciation of VN sounds and tones; using English stress patterns which so not exist in Vietnamese.

Then again, many Vietnamese are not expecting you to speak Vietnamese, so they switch off and don't listen. Also, it is common that if they don't agree with or want to hear what you are saying, they also switch off.

Restaurant waiting staff are notorious.  They bring out what the kitchen happens to have, which may or may not be anything like you ordered.

Just keep plugging away and do your best.  Good luck.

Now I have been in Vietnam 10 years but don't feel that my Vietnamese has improved much in the last few years. I rarely speak English and get by with what I have.  I still get frustrated when I am not understood but still enjoy trying to figure out the language. Perhaps some time I will have an epiphany and understand all.

I do believe wrote:

Now I have been in Vietnam 10 years but don't feel that my Vietnamese has improved much in the last few years. I rarely speak English and get by with what I have.  I still get frustrated when I am not understood but still enjoy trying to figure out the language. Perhaps some time I will have an epiphany and understand all.

I hope you don't take this personally, but when was the last time you had your hearing tested?  We all lose hearing with age, particularly in the higher register where the vowels that give meaning to Viet words reside.  For those who work in industrial environments, as you may, partial loss is even more likely.  I know that I lost part of my high register hearing by running farm tractors without ear plugs.  A slight loss could make your ability to properly distinguish and produce vowel tones difficult.  For older native speakers, there are context clues for hearing and muscle memory (the mouth "knows" how to move) for speaking.

Let me relate two anecdotes.  I once asked one of my TA's how a Vietnamese with not total but impaired hearing learned to speak.  His immediate answer was "They don't."   In another case there is a Vietnamese man in Honolulu with a rather severe speech impediment.  I once asked another Vietnamese if he was easier to understand in Vietnamese and the answer was that he was a lot harder to understand in Vietnamese than in English.

I notice that foreigners who accomplish real fluency in Vietnamese, such as those on YouTube, are almost exclusively in their 20's.  I did once meet an American my own age who reputedly had amazing fluency but he had spent three tours during the war as an interrogator and had continued to use the language in Honolulu, mostly to enhance relations with Vietnamese women.  Gradual minor hearing loss, even if slight, may be a real obstacle tlo fluency for those of us who are older.

"Perhaps sometime ... I will understand all."
No, unfortunately, that is never going to happen. It is better to aim for an achievable target. Such as learning a few new words each day while reading Tuoi Tre or Thanh Nien newspapers, or having a teacher check your pronunciation or introduce you to Vietnamese phrases, concepts, and grammar. No matter how much Vietnamese you already know   there is still so much to learn. Just pick up a dictionary and see how many words you don't know. Terrifying  isn't it?

THIGV wrote:

I do believe wrote:

Now I have been in Vietnam 10 years but don't feel that my Vietnamese has improved much in the last few years. I rarely speak English and get by with what I have.  I still get frustrated when I am not understood but still enjoy trying to figure out the language. Perhaps some time I will have an epiphany and understand all.

I hope you don't take this personally, but when was the last time you had your hearing tested?  We all lose hearing with age, particularly in the higher register where the vowels that give meaning to Viet words reside.  For those who work in industrial environments, as you may, partial loss is even more likely.  I know that I lost part of my high register hearing by running farm tractors without ear plugs.  A slight loss could make your ability to properly distinguish and produce vowel tones difficult.  For older native speakers, there are context clues for hearing and muscle memory (the mouth "knows" how to move) for speaking.

Let me relate two anecdotes.  I once asked one of my TA's how a Vietnamese with not total but impaired hearing learned to speak.  His immediate answer was "They don't."   In another case there is a Vietnamese man in Honolulu with a rather severe speech impediment.  I once asked another Vietnamese if he was easier to understand in Vietnamese and the answer was that he was a lot harder to understand in Vietnamese than in English.

I notice that foreigners who accomplish real fluency in Vietnamese, such as those on YouTube, are almost exclusively in their 20's.  I did once meet an American my own age who reputedly had amazing fluency but he had spent three tours during the war as an interrogator and had continued to use the language in Honolulu, mostly to enhance relations with Vietnamese women.  Gradual minor hearing loss, even if slight, may be a real obstacle tlo fluency for those of us who are older.

While the above is correct, language learning starts in the womb. Our brains then are "tuned" the it's native language. Just like some who are more adept at learning music or have perfect pitch, some people will never be able to FULLY differentiate the different sounds of a foreign language.
Some can so it almost like a native; some never will be able to and most are in-between.

Next, there is another issue. Why are phone calls more distracting than talking in person?
because our brains use all sorts of clues to determine words. Reading lips is number one. SO even if you make the correct sound, the person you are speaking to, may not understand because your mouth shape may not be correct.
Also, our brains start to guess the word coming at the first sound. That guess may be predicated on your look. Therefore, even if you say a word, phase PERFECTLY, the receiver, the native speaker, may not be anticipating those words from your lips. It may take repeated tries, before the receiver comprehends what's going on, if then.

These same issue exist for all speakers of non-native languages. Vietnamese is particularily hard for a westerner because it is tonal.

Good luck, don't give up. 
One day, as I pull up to the gas tank, raise my seat, take off the filler cap, and say, "Day Bun", I hope they stop looking at me like I'm ordering a sandwich.!

Wxx3 wrote:

.... language learning starts in the womb. Our brains then are "tuned" the it's native language.

While this seems intuitively true, it runs contrary to the critical period hypothesis of language learning.  In a few words, this is that one can develop more than one L1 language as long as exposure occurs before about age 5.  One similar thing I have noticed, non-scientifically, is that when children are born to couples that speak two different languages, they first learn the language of the mother, then the language of their surroundings, then perhaps the language of the father.

Wxx3 wrote:

Vietnamese is particularily hard for a westerner because it is tonal.

I was once told by a native Mandarin speaker that he found learning Vietnamese very difficult.   I commented that since Mandarin is tonal, I would think it would be easy.  He responded that getting the tones wrong in Chinese languages will make one sound funny but you can still be understood although with some difficulty.  Getting the tones wrong in Vietnamese totally changes the meaning of words.  Conversely, Vietnamese have told me that Chinese languages are easy for them to learn.

Wxx3 wrote:

One day, as I pull up to the gas tank, raise my seat, take off the filler cap, and say, "Day Bun", I hope they stop looking at me like I'm ordering a sandwich.!

Did you say đầy bốn, literally "fill four," to signify that you wanted 40,000 VND worth?  I have no idea how to pronounce that properly.    I always just held up fingers, one for each 10,000.  My wife did the same and I think her Vietnamese is pretty good, having been learned in the womb. 

Just need to say bốn mươi nghin, most in the south say  đầy if you want it filled.

Posters above make some interesting points:

“We all lose hearing with age”
-  True. I mostly now cannot hear the letter 's', no matter if it is at the front or back of a word.

After about 45 years of age, if we have not already learnt a tonal language, we cannot hear the tones properly. Because we cannot hear them, we cannot correctly reproduce them. This is a physical restriction, not a mental one.

“Why are phone calls more distracting than talking in person? “
-  As well as the reasons given, another reason is that phones restrict the frequencies transmitted.  Secondly, should the sender be shouting down the phone, as happens in VN, the telephone transmission volume is also restricted to avoid over modulation.  So either way you not getting all the original sound.  Thirdly, the original sound can be electronically distorted in transmission.

“I was once told by a native Mandarin speaker that he found learning Vietnamese very difficult.”
-  This could be because Vietnamese has more tones than Mandarin, and all VN tones have  quite different tonal qualities to Mandarin tones (even if I appear to give them similar names below).

Tones in Mandarin: high tone, low tone, low rising tone, high falling tone, neutral tone
Tones in Vietnamese: mid tone, high rising tone, low falling tone, low rising tone, high broken tone, low broken tone.

Importantly, Vietnamese keeps the full tonal quality of the all syllables in the word, whereas Mandarin Chinese has tone sandhi, in which the tone of the first syllable in a bisyllabic word will change depending on the following tone in the second syllable.  For example, Đả đảo (to overthrow) in Vietnamese comes directly from the Chinese 打倒 dǎdǎo. But in Chinese the low rising tone on the first syllable is pronounced as a high tone, due to tone sandhi.  The Chinese respondent could have had trouble with this difference, too

Vietnamese sounds are very different to Chinese sounds. And in Vietnamese there are very many more possible combinations of tones, vowels and consanants than there are in Chinese.
(Sorry for getting a bit long winded on this reply.)

Instead of saying “"Day Bun", you should be saying “Đầy bình” = Fill up the tank.

Wxx3 wrote:

One day, as I pull up to the gas tank, raise my seat, take off the filler cap, and say, "Day Bun", I hope they stop looking at me like I'm ordering a sandwich.!

I think “đầy bình”, not “đầy bốn” because “đầy bốn” has no meaning in Vietnamese. “Đầy bình” means  “fill fully the tank”

I couldn't guess what he meant until reading your comments

Rgds,
Ni

I reckon the problem might be the Vietnamese accent (northern, central or southern accent). Even the Vietnamese in the south does not entirely understand the norther accent or some part of central accent and vice versa. The central Vietnamese can understand in either side much better than the both and they can even speak in either northern or southern accent like they are from there.

Besides, your pronunciation and emphasis might be the big problem too as many foreigners have given up Vietnamese language.

Last but not least, you can show your Vietnamese speaking through youtube so that other can give better suggestion

Have fun with Vietnamese language!

colinoscapee wrote:

Just need to say bốn mươi nghin, most in the south say  đầy if you want it filled.

Isn't 'nghìn' northern dialect?..I thought the southern equivalent was 'ngàn'.

Anyway, I usually say 'bốn mươi lăm' (forty five) and it's understood. Occasionally, have to repeat, but  maybe that's because not many people buy petrol in such odd denomination. i.e. forty five as opposed to forty or fifty.

sanooku wrote:

Isn't 'nghìn' northern dialect?..I thought the southern equivalent was 'ngàn'.

You're correct, but both words are used and understood by everyone everywhere.  No need to switch them around.

I struggle also, but having read so many self teach books and then hiring a tutor I can see why.

Some words, make that a lot of Vietnamese words have different meanings depending on various accents

Even when spelt the same it is easy to make a mistake in pronunciations