I'm reading Modern German Pronunciation, 2nd edition by Christopher Hall and I have a question regarding the /p/. I hold piece of paper directly in front of my lips and first I say the word Paar. I see the paper moving as I pronounce the aspirated /p/. Then I say the word Spar and I see the paper moving again. Christopher Hall says that there is no aspiration when the /p/ follows /ʃ/ but I found that the paper always moves. What am I doing wrong? Is there any other way to demonstrate this?
Don't trouble with holding paper in front of your mouth, I never do. I think when you pronounce "schbaren" that is okay (at least in the south of Germany people pronounce it that way). Listen to speakers on the radio and forget the complicated things they tell you in books about pronunciation. Or try to get audio material from libraries. /p/ and /b/ sound different, that's right, /p/ has tension of the muscles of the lips and the lisps open with a slight explosion. But don't worry whether your paper moves or not, it doesn't matter. The more you hear and speak the better you will do.