diff --git a/pjmedia/build/Makefile b/pjmedia/build/Makefile
index 9b347ed..7cf6012 100644
--- a/pjmedia/build/Makefile
+++ b/pjmedia/build/Makefile
@@ -160,7 +160,7 @@
 	$(MAKE) -f $(RULES_MAK) APP=PJMEDIA_CODEC app=pjmedia-codec $@
 	$(MAKE) -f $(RULES_MAK) APP=PJMEDIA_TEST app=pjmedia-test $@
 	$(MAKE) -f $(RULES_MAK) APP=PJMEDIA_CODEC app=pjmedia-codec $@
-	@if test "$@" == "depend"; then \
+	@if test "$@" = "depend"; then \
 	  echo '$(PJMEDIA_LIB): .pjmedia-$(MACHINE_NAME)-$(OS_NAME)-$(CC_NAME).depend' >> .pjmedia-$(MACHINE_NAME)-$(OS_NAME)-$(CC_NAME).depend; \
 	  echo '$(PJMEDIA_CODEC_LIB): .pjmedia-codec-$(MACHINE_NAME)-$(OS_NAME)-$(CC_NAME).depend' >> .pjmedia-codec-$(MACHINE_NAME)-$(OS_NAME)-$(CC_NAME).depend; \
 	  echo '$(PJMEDIA_TEST_EXE): $(PJMEDIA_LIB) $(PJMEDIA_CODEC_LIB)' >> .pjmedia-test-$(MACHINE_NAME)-$(OS_NAME)-$(CC_NAME).depend; \
diff --git a/pjmedia/build/os-win32.mak b/pjmedia/build/os-win32.mak
index ffd043b..9a7c836 100644
--- a/pjmedia/build/os-win32.mak
+++ b/pjmedia/build/os-win32.mak
@@ -13,8 +13,9 @@
 export OS_CFLAGS += -DPA_NO_ASIO -DPA_NO_DS
 
 # Example:
-#  to activate Null sound, uncomment this line below.
+#  to activate Null sound, uncomment these two lines below.
 #export SOUND_OBJS = $(NULLSOUND_OBJS)
+#export OS_CFLAGS += $(CC_DEF)PJMEDIA_HAS_NULL_SOUND
 
 # Example:
 #  to include only GSM and exclude Speex codec, uncomment the "export" line below.
diff --git a/pjmedia/include/pjmedia.h b/pjmedia/include/pjmedia.h
index 9a8c423..8cdc0b7 100644
--- a/pjmedia/include/pjmedia.h
+++ b/pjmedia/include/pjmedia.h
@@ -38,6 +38,7 @@
 #include <pjmedia/rtp.h>
 #include <pjmedia/sdp.h>
 #include <pjmedia/sdp_neg.h>
+#include <pjmedia/silencedet.h>
 #include <pjmedia/session.h>
 #include <pjmedia/sound.h>
 #include <pjmedia/sound_port.h>
diff --git a/pjmedia/include/pjmedia/silencedet.h b/pjmedia/include/pjmedia/silencedet.h
index f251c08..4e82397 100644
--- a/pjmedia/include/pjmedia/silencedet.h
+++ b/pjmedia/include/pjmedia/silencedet.h
@@ -130,7 +130,14 @@
 					      pj_uint32_t level);
 
 
+/**
+ * Declaration linear2ulaw
+ */
+unsigned char linear2ulaw(int pcm_val);
+
+
 PJ_END_DECL
 
+
 #endif	/* __PJMEDIA_SILENCE_DET_H__ */
 
diff --git a/pjmedia/src/pjmedia/errno.c b/pjmedia/src/pjmedia/errno.c
index 7ea7af8..86c78d5 100644
--- a/pjmedia/src/pjmedia/errno.c
+++ b/pjmedia/src/pjmedia/errno.c
@@ -145,6 +145,7 @@
 #if defined(PJ_HAS_ERROR_STRING) && (PJ_HAS_ERROR_STRING != 0)
 
     /* See if the error comes from PortAudio. */
+#if defined(PJMEDIA_HAS_PORTAUDIO_SOUND) && PJMEDIA_HAS_PORTAUDIO_SOUND!=0
     if (statcode >= PJMEDIA_ERRNO_FROM_PORTAUDIO(paNotInitialized) &&
 	statcode <  PJMEDIA_ERRNO_FROM_PORTAUDIO(paNotInitialized + 10000))
     {
@@ -159,7 +160,9 @@
 	pj_strncpy_with_null(&errstr, &msg, bufsize);
 	return errstr;
 
-    } else if (statcode >= PJMEDIA_ERRNO_START && 
+    } else 
+#endif	/* PJMEDIA_HAS_PORTAUDIO_SOUND */
+    if (statcode >= PJMEDIA_ERRNO_START && 
 	       statcode < PJMEDIA_ERRNO_START + PJ_ERRNO_SPACE_SIZE)
     {
 	/* Find the error in the table.