Plum IVR Support

I am having a problem with my app. When the app starts, sometimes the voice comes on and says "I didn't understand you" then it goes into the prompt. Or it will begin the prompt and then cut off and say, "Sorry I didn't understand you". Even though no buttons were pushed. I am not sure if it is expecting a voice response though. I don't want it to expect a voice, only DTMF

This is the beginning of the app. It is only an excerpt and not the full page

<?php
include("application.php");
echo ("<?xml version=\"1.0\"?>\n");
echo ("<vxml version=\"2.0\">\n");
?>

<property name="interdigittimeout" value="2s"/>
<form id="form_Main">
<field name="digit1" type="digits">
<prompt bargein="true">
Welcome to <?=$CFG->title?> telephone service<break time="400ms"/>
Please enter your <?=$CFG->label?> account number
</prompt>
<filled>
<log label="Filled">Your entry was <value expr="digit1"/></log>
</filled>
</field>


Please advise.

Hello,

The default listening mode for a VoiceXML browser should always be both DTMF and Voice. This can be modified by using the IVR global property inputmodes:
This will disable all speech bargein and will only allow speech input if you make use of the <record> tag. If you are planning on adding speech recognition to your IVR application it is a good idea to have the initial prompt be non-bargeable. This gives the input detection IVR system time to adapt to the background noise and avoid as many false bargeins as possible.

Regards,
Plum Support