Unable to find and load OpenAL library

[kestrel]

i install joal in my windows, and run the demo code.

the exception is :

Exception in thread "main" java.lang.RuntimeException: Can not get proc address for method "alcCaptureCloseDevice": Couldn't set value of field "_addressof_alcCaptureCloseDevice" in class net.java.games.joal.impl.ALCProcAddressTable
   at com.sun.gluegen.runtime.ProcAddressHelper.resetProcAddressTable(ProcAddressHelper.java:68)
   at net.java.games.joal.impl.ALProcAddressLookup.resetALCProcAddressTable(ALProcAddressLookup.java:109)
   at net.java.games.joal.impl.ALCImpl.alcOpenDevice(ALCImpl.java:342)
   at net.java.games.joal.util.ALut.alutInit(ALut.java:69)
   at joal.JOALSoundMan.initOpenAL(JOALSoundMan.java:62)
   at joal.JOALSoundMan.<init>(JOALSoundMan.java:53)
   at joal.MovingListener2.main(MovingListener2.java:13)
Caused by: java.lang.RuntimeException: Unable to find and load OpenAL library
   at net.java.games.joal.impl.ALProcAddressLookup$DynamicLookup.dynamicLookupFunction(ALProcAddressLookup.java:66)
   at com.sun.gluegen.runtime.ProcAddressHelper.resetProcAddressTable(ProcAddressHelper.java:64)
   ... 6 more

what is the problem, Iwhy i cant find the library.
I copy the .dll to jdk/jre/lib/ext, is it right ?
or any thing others i go to set?
plz help.