--- configure.ac	(Asterisk 13.20)
+++ configure.ac	(working copy)
@@ -2149,5 +2149,10 @@
 
-# possible places for oss definitions
+# possible places for OSS definitions
+# Linux
 AST_EXT_LIB_CHECK([OSS], [ossaudio], [], [linux/soundcard.h])
+# NetBSD: Search for a symbol like _oss_ioctl, to link its OSS Audio Emulation Library.
+AST_EXT_LIB_CHECK([OSS], [ossaudio], [_oss_ioctl], [sys/soundcard.h])
+# FreeBSD
 AST_EXT_LIB_CHECK([OSS], [ossaudio], [], [sys/soundcard.h])
+# OpenBSD
 AST_EXT_LIB_CHECK([OSS], [ossaudio], [oss_ioctl_mixer], [soundcard.h])