diff --git a/src/common/debug.c b/src/common/debug.c
index e4677e7..fe4de48 100644
--- a/src/common/debug.c
+++ b/src/common/debug.c
@@ -23,6 +23,7 @@
 #include <stdlib.h>
 #include <stdint.h>
 #include <errno.h>
+#include <math.h>
 #include "sample.h"
 #include "debug.h"
 #include "display.h"
@@ -118,6 +119,26 @@ const char *debug_amplitude(double level)
 	return text;
 }
 
+#define level2db(level)         (20 * log10(level))
+
+const char *debug_db(double level_db)
+{
+	static char text[128];
+	int l;
+
+	strcpy(text, ":  .  :  .  :  .  :  .  :  .  :  .  :  .  :  .  :   ");
+	if (level_db <= 0.0)
+		return text;
+	l = (int)round(level2db(level_db));
+	if (l > 3)
+		return text;
+	if (l < -48)
+		return text;
+	text[l + 48] = '*';
+
+	return text;
+}
+
 void debug_list_cat(void)
 {
 	int i;
diff --git a/src/common/debug.h b/src/common/debug.h
index 989ee9f..b5b3e2e 100644
--- a/src/common/debug.h
+++ b/src/common/debug.h
@@ -27,6 +27,7 @@
 void _printdebug(const char *file, const char *function, int line, int cat, int level, int chan, const char *fmt, ...) __attribute__ ((__format__ (__printf__, 7, 8)));
 
 const char *debug_amplitude(double level);
+const char *debug_db(double level_db);
 
 void debug_list_cat(void);
 int parse_debug_opt(const char *opt);
diff --git a/src/test/test_filter.c b/src/test/test_filter.c
index d78578a..0f7c6b9 100644
--- a/src/test/test_filter.c
+++ b/src/test/test_filter.c
@@ -13,31 +13,12 @@
 
 static double get_level(double *samples)
 {
-#if 0
-	int i;
-	double last = 0, envelope = 0;
-	int up = 0;
-
-	for (i = SAMPLERATE/2; i < SAMPLERATE; i++) {
-		if (last < samples[i]) {
-			up = 1;
-		} else if (last > samples[i]) {
-			if (up) {
-				if (last > envelope)
-					envelope = last;
-			}
-			up = 0;
-		}
-		last = samples[i];
-	}
-#else
 	int i;
 	double envelope = 0;
 	for (i = SAMPLERATE/2; i < SAMPLERATE; i++) {
 		if (samples[i] > envelope)
 			envelope = samples[i];
 	}
-#endif
 
 	return envelope;
 }
@@ -72,7 +53,7 @@ int main(void)
 		gen_samples(samples, (double)i);
 		filter_process(&filter_low, samples, SAMPLERATE);
 		level = get_level(samples);
-		printf("%4d Hz: %.1f dB", i, level2db(level));
+		printf("%s%4d Hz: %.1f dB", debug_db(level), i, level2db(level));
 		if (i == 1000)
 			printf(" cutoff\n");
 		else if (i == 2000)
@@ -91,7 +72,7 @@ int main(void)
 		gen_samples(samples, (double)i);
 		filter_process(&filter_high, samples, SAMPLERATE);
 		level = get_level(samples);
-		printf("%4d Hz: %.1f dB", i, level2db(level));
+		printf("%s%4d Hz: %.1f dB", debug_db(level), i, level2db(level));
 		if (i == 2000)
 			printf(" cutoff\n");
 		else if (i == 1000)
@@ -112,7 +93,7 @@ int main(void)
 		filter_process(&filter_low, samples, SAMPLERATE);
 		filter_process(&filter_high, samples, SAMPLERATE);
 		level = get_level(samples);
-		printf("%4d Hz: %.1f dB", i, level2db(level));
+		printf("%s%4d Hz: %.1f dB", debug_db(level), i, level2db(level));
 		if (i == 1000)
 			printf(" cutoff high\n");
 		else if (i == 2000)