diff --git a/test/001_highsnr_stdio_audio/test_multimode_tx.py b/test/001_highsnr_stdio_audio/test_multimode_tx.py
index 61aa53aa..69da149a 100644
--- a/test/001_highsnr_stdio_audio/test_multimode_tx.py
+++ b/test/001_highsnr_stdio_audio/test_multimode_tx.py
@@ -20,24 +20,32 @@ parser = argparse.ArgumentParser(description='FreeDATA TEST')
 parser.add_argument('--bursts', dest="N_BURSTS", default=0, type=int)
 parser.add_argument('--framesperburst', dest="N_FRAMES_PER_BURST", default=0, type=int)
 parser.add_argument('--delay', dest="DELAY_BETWEEN_BURSTS", default=0, type=int)
-parser.add_argument('--audiooutput', dest="AUDIO_OUTPUT", default=0, type=int) 
+parser.add_argument('--audiodev', dest="AUDIO_OUTPUT_DEVICE", default=-1, type=int, help="audio output device number to use") 
+parser.add_argument('--list', dest="LIST", action="store_true", help="list audio devices by number and exit")  
 
 args = parser.parse_args()
 
+if args.LIST:
+    p = pyaudio.PyAudio()
+    for dev in range(0,p.get_device_count()):
+        print("audiodev: ", dev, p.get_device_info_by_index(dev)["name"])
+    quit()
+
 N_BURSTS = args.N_BURSTS
 N_FRAMES_PER_BURST = args.N_FRAMES_PER_BURST
 DELAY_BETWEEN_BURSTS = args.DELAY_BETWEEN_BURSTS/1000
-AUDIO_OUTPUT_DEVICE = args.AUDIO_OUTPUT
+AUDIO_OUTPUT_DEVICE = args.AUDIO_OUTPUT_DEVICE
 
 
 # AUDIO PARAMETERS
 AUDIO_FRAMES_PER_BUFFER = 2048 
 MODEM_SAMPLE_RATE = codec2.api.FREEDV_FS_8000
 AUDIO_SAMPLE_RATE_TX = 48000
+assert (AUDIO_SAMPLE_RATE_TX % MODEM_SAMPLE_RATE) == 0
 
 
 
-if AUDIO_OUTPUT_DEVICE != 0: 
+if AUDIO_OUTPUT_DEVICE != -1: 
     # pyaudio init
     p = pyaudio.PyAudio()
     stream_tx = p.open(format=pyaudio.paInt16,
@@ -48,7 +56,7 @@ if AUDIO_OUTPUT_DEVICE != 0:
                             output_device_index=AUDIO_OUTPUT_DEVICE,  
                             )      
 
-modes = [14,10,12]
+modes = [codec2.api.FREEDV_MODE_DATAC0, codec2.api.FREEDV_MODE_DATAC1, codec2.api.FREEDV_MODE_DATAC3]
 for m in modes:
 
     
@@ -105,7 +113,7 @@ for m in modes:
         
 
         # check if we want to use an audio device or stdout
-        if AUDIO_OUTPUT_DEVICE != 0: 
+        if AUDIO_OUTPUT_DEVICE != -1: 
                 
             # sample rate conversion from 8000Hz to 48000Hz
             audio = audioop.ratecv(txbuffer,2,1,MODEM_SAMPLE_RATE, AUDIO_SAMPLE_RATE_TX, None)                                           
diff --git a/test/codec2.py b/test/codec2.py
index e51d25a9..a1777a9c 100644
--- a/test/codec2.py
+++ b/test/codec2.py
@@ -72,6 +72,9 @@ api.freedv_get_n_tx_modem_samples.restype = c_int
 
 
 api.FREEDV_FS_8000 = 8000
+api.FREEDV_MODE_DATAC1 = 10
+api.FREEDV_MODE_DATAC3 = 12
+api.FREEDV_MODE_DATAC0 = 14