diff --git a/platform/posix/wav_util.c b/platform/posix/wav_util.c
index 962284522..8c4be2fdb 100644
--- a/platform/posix/wav_util.c
+++ b/platform/posix/wav_util.c
@@ -44,6 +44,7 @@
 
 #include "wav_util.h"
 #include "btstack_util.h"
+#include "btstack_debug.h"
 
 static int wav_reader_fd;
 static int bytes_per_sample = 2;
@@ -164,7 +165,7 @@ int wav_writer_write_int16(int num_samples, int16_t * data){
 int wav_reader_open(const char * filepath){
     wav_reader_fd = open(filepath, O_RDONLY); 
     if (!wav_reader_fd) {
-        printf("Can't open file %s", filepath);
+        log_error("Can't open file %s", filepath);
         return 1;
     }
 
@@ -173,6 +174,10 @@ int wav_reader_open(const char * filepath){
 
     int num_channels = little_endian_read_16(buf, 22);
     int block_align = little_endian_read_16(buf, 32);
+    if (num_channels != 1 && num_channels != 2) {
+        log_error("Unexpected num channels %d", num_channels);
+        return 1;
+    }
     bytes_per_sample = block_align/num_channels;
     if (bytes_per_sample > 2){
         bytes_per_sample = bytes_per_sample/8;
diff --git a/src/classic/btstack_cvsd_plc.c b/src/classic/btstack_cvsd_plc.c
index 8a6f18d02..8c52ad36b 100644
--- a/src/classic/btstack_cvsd_plc.c
+++ b/src/classic/btstack_cvsd_plc.c
@@ -258,7 +258,7 @@ void btstack_cvsd_plc_process_data(btstack_cvsd_plc_state_t * state, int8_t * in
         btstack_cvsd_plc_good_frame(state, in, out);
         state->good_frames_nr++;
         if (state->good_frames_nr == 1){
-            printf("First good frame at index %d\n", state->frame_count-1);
+            log_info("First good frame at index %d\n", state->frame_count-1);
         }        
     }
 }
@@ -279,12 +279,12 @@ void btstack_cvsd_plc_mark_bad_frame(btstack_cvsd_plc_state_t * state, int8_t *
         memcpy(out, in, size);
         state->good_frames_nr++;
         if (state->good_frames_nr == 1){
-            printf("First good frame at index %d\n", state->frame_count-1);
+            log_info("First good frame at index %d\n", state->frame_count-1);
         }        
     }
 }
 
 void btstack_cvsd_dump_statistics(btstack_cvsd_plc_state_t * state){
-    printf("Good frames: %d\n", state->good_frames_nr);
-    printf("Bad frames: %d\n", state->bad_frames_nr);
+    log_info("Good frames: %d\n", state->good_frames_nr);
+    log_info("Bad frames: %d\n", state->bad_frames_nr);
 }
diff --git a/test/hfp/Makefile b/test/hfp/Makefile
index 40d2a6c6f..2a5c4877b 100644
--- a/test/hfp/Makefile
+++ b/test/hfp/Makefile
@@ -79,7 +79,7 @@ cvsd_plc_test: ${COMMON_OBJ} btstack_cvsd_plc.o wav_util.o cvsd_plc_test.c
 	${CC} $^ ${CFLAGS} ${LDFLAGS} -o $@
 
 test: all
-	mkdir -p result
+	mkdir -p results
 	./hfp_ag_parser_test
 	./hfp_ag_client_test
 	./hfp_hf_parser_test
diff --git a/test/hfp/cvsd_plc_test.c b/test/hfp/cvsd_plc_test.c
index 7cd6a39f6..0dbaaeb38 100644
--- a/test/hfp/cvsd_plc_test.c
+++ b/test/hfp/cvsd_plc_test.c
@@ -117,7 +117,7 @@ static void introduce_bad_frames_to_wav_file(const char * in_filename, const cha
 }
 
 static void process_wav_file_with_plc(const char * in_filename, const char * out_filename){
-    printf("\nProcess %s -> %s\n", in_filename, out_filename);
+    // printf("\nProcess %s -> %s\n", in_filename, out_filename);
     btstack_cvsd_plc_init(&plc_state);
     wav_writer_open(out_filename, 1, 8000);
     wav_reader_open(in_filename);
@@ -133,10 +133,10 @@ static void process_wav_file_with_plc(const char * in_filename, const char * out
 }
 
 static void mark_bad_frames_wav_file(const char * in_filename, const char * out_filename){
-    printf("\nMark bad frame %s -> %s\n", in_filename, out_filename);
+    // printf("\nMark bad frame %s -> %s\n", in_filename, out_filename);
     btstack_cvsd_plc_init(&plc_state);
-    wav_writer_open(out_filename, 1, 8000);
-    wav_reader_open(in_filename);
+    CHECK_EQUAL(wav_writer_open(out_filename, 1, 8000), 0);
+    CHECK_EQUAL(wav_reader_open(in_filename), 0);
     
     while (wav_reader_read_int8(audio_samples_per_frame, audio_frame_in)){
         int8_t audio_frame_out[audio_samples_per_frame];
@@ -161,8 +161,8 @@ TEST(CVSD_PLC, CountEqBytes){
 
 TEST(CVSD_PLC, TestLiveWavFile){
     int corruption_step = 10;
-    introduce_bad_frames_to_wav_file("data/input/sco_input.wav", "results/sco_input.wav", 0);
-    introduce_bad_frames_to_wav_file("data/input/sco_input.wav", "results/sco_input_with_bad_frames.wav", corruption_step);
+    introduce_bad_frames_to_wav_file("data/sco_input.wav", "results/sco_input.wav", 0);
+    introduce_bad_frames_to_wav_file("data/sco_input.wav", "results/sco_input_with_bad_frames.wav", corruption_step);
     
     mark_bad_frames_wav_file("results/sco_input.wav", "results/sco_input_detected_frames.wav");
     process_wav_file_with_plc("results/sco_input.wav", "results/sco_input_after_plc.wav");