QUick question...In words like femmes is the S always muted at the end even if the comes before a vowel?
I believe this is an optional liaison. It's not incorrect to pronounce the "s" if the next word begins with a vowel, but it's also not required.
Ça me fait chier! How do you hear the difference between the singular and plural noun?
You will hear it clearly in the article "les" which tells you it is a plural noun. The other possibilities are "une femme américaine" and "des femmes américaines". You should be able to identify each of these from the audio.
Technically it would be the latter, but in practice people are usually referring to US citizens.
Its inconvinient that s'es for plurals are not pronounced what so ever.
So you will learn to identify other ways to tell if the noun is plural, e.g., listening to the article that precedes it: la, une, les, des. If you can hear the difference there, the problem is solved.
I put the American Females (don't know why?) but surely this should also be correct or is there another word in French for female other than femme?
No, it is not correct. "Femmes" is not translated as "females"; that would be les femelles. In the same way, you will never translate "elles" as "the girls", "the women" or "the females" any more than you would translate "ils" as "the men", "the males", "the boys" or "the guys". I.e., just because there is a gender identification in French does not mean that the gender is translated into English. For example: un enseignant = a teacher (not a "male teacher"), une enseignante = a teacher (not a "female teacher"). Same with chat/chatte. In English, they are both cats. If you must make a point of the gender, you would use the FR "femelle" to specify "female" and "mâle" to specify "male".
Well, it's optional, but in my experience very common.
Here's more information about liaison: http://french.about.com/library/pronunciation/bl-liaisons-o.htm
it's almost IMPOSSIBLE to determine whether the spoken word is singular or plural and you should not mark an answer incorrect when the basic translation is right. The spoken voices sound distorted
You are learning. Sometimes it takes a little practice to distinguish sounds.
"Les femmes américaines" can only be plural.
If it were singular, it would be "La femme américaine".
"La" is a different sound from "Les". If you need to practice hearing the difference, I recommend http://www.acapela-group.com/ You can pick a French voice, put "La femme américaine; les femmes américaines" in the box and click on "listen!" Try different French voices.
Btw, although I agree that some of the spoken examples on DL are off, this one sounds just fine to me.