diff --git a/Makefile b/Makefile
index 942fb4a..73f9f95 100644
--- a/Makefile
+++ b/Makefile
@@ -195,15 +195,15 @@ $(error Invalid target: T=$(T))
 endif
 export T
 
-# Select sound language
-LANGUAGE_SOUND_FOLDER = config/_default_cfg_src_/res/$(LANG)
-ifeq ($(LANG),)
-$(error Please specify the sound language in the command line: LANG=<languageAbbrev>)
+# Select audio source
+AUDIO_FOLDER = config/_default_cfg_src_/res/$(AUDIO)
+ifeq ($(AUDIO),)
+$(error Please specify the sound language in the command line: AUDIO=<audioName>)
 endif
-ifeq ($(wildcard $(LANGUAGE_SOUND_FOLDER)),)
-$(error Invalid target: LANG=$(LANG))
+ifeq ($(wildcard $(AUDIO_FOLDER)),)
+$(error Invalid target: AUDIO=$(AUDIO))
 endif
-export LANG
+export AUDIO
 
 KBUILD_OUTPUT := $(KBUILD_OUTPUT)/$(T)
 
diff --git a/README.md b/README.md
index d343337..c4bfb83 100644
--- a/README.md
+++ b/README.md
@@ -81,10 +81,10 @@ and recompile with `./build.sh`!
 
 ### Language support
 
-The `LANG` environment variable can be set when running the `build.sh` script to load sound files
-for languages other than the default English. For example, running `LANG=cn ./build.sh` will load sounds files from 
+The `AUDIO` environment variable can be set when running the `build.sh` script to load sound files
+for languages other than the default English. For example, running `AUDIO=cn ./build.sh` will load sounds files from 
 `config/_default_cfg_src_/res/cn/` instead of the default `en/` folder. 
 
 The current languages supported with sound files are English (`en`) and Chinese (`cn`). Other languages 
 (or other sets of custom sounds) may be added by adding all the correct sound files into a 
-`config/_default_cfg_src_/res/<custom_language>/` directory and building with `LANG=<custom_language> ./build.sh`.
\ No newline at end of file
+`config/_default_cfg_src_/res/<custom_sounds>/` directory and building with `AUDIO=<custom_sounds> ./build.sh`.
\ No newline at end of file
diff --git a/build.sh b/build.sh
index 7f35757..9b46afa 100755
--- a/build.sh
+++ b/build.sh
@@ -1,7 +1,7 @@
 #!/bin/bash
 
-# use LANG environment variable, default to "en"
-LANG="${LANG:-en}"
+# use AUDIO environment variable, default to "en"
+AUDIO="${AUDIO:-en}"
 
 make -j T=open_source DEBUG=1 >log.txt 2>&1
 
diff --git a/services/bt_app/Makefile b/services/bt_app/Makefile
index e74116e..c5624b9 100644
--- a/services/bt_app/Makefile
+++ b/services/bt_app/Makefile
@@ -9,7 +9,7 @@ ifeq ($(VOICE_DATAPATH_TYPE),gsound)
 obj_cpp += $(patsubst $(cur_dir)%,%,$(wildcard $(cur_dir)/app_voice/app_$(VOICE_DATAPATH_TYPE)/*.cpp))
 endif
 
-obj_mp3 := $(patsubst $(cur_dir)%,%,$(wildcard ../../config/_default_cfg_src_/res/$(LANG)/*.mp3))
+obj_mp3 := $(patsubst $(cur_dir)%,%,$(wildcard ../../config/_default_cfg_src_/res/$(AUDIO)/*.mp3))
 
 obj-y := $(obj_mp3:.mp3=.snd.o) $(obj_mp3:.mp3=.snd.cpp) $(obj_c:.c=.o) $(obj_s:.S=.o) $(obj_cpp:.cpp=.o)