Asterisk Dialplan: Installing Custom Prompts (Latest Versions)

Custom voice prompts are a critical part of professional IVR systems. Default Asterisk sounds are generic, while businesses need branded, clear, and context-specific audio messages.

Installing prompts correctly is not just copying audio files. The audio format, directory structure, permissions, and codec compatibility must all be correct for reliable playback.

This guide explains how to install custom prompts in modern Asterisk (PJSIP-based deployments), including real production troubleshooting steps.

Where Asterisk Stores Sound Files

Main sounds directory:

/var/lib/asterisk/sounds/

Recommended location for custom prompts:

/var/lib/asterisk/sounds/custom/

Example prompt path:

/var/lib/asterisk/sounds/custom/welcome.wav

Supported Audio Formats in Asterisk

For best compatibility with telephony:

• Mono channel audio
• 8000 Hz sample rate
• 16-bit PCM WAV format

Incorrect formats often cause:

• Silence during playback
• Distorted or fast audio
• Codec negotiation failures

Step 1 — Prepare the Audio File

Convert audio using ffmpeg:

ffmpeg -i input.mp3 -ar 8000 -ac 1 -acodec pcm_s16le welcome.wav

This ensures telephony-safe WAV format.

Step 2 — Copy Prompt to Asterisk Sounds Directory

sudo mkdir -p /var/lib/asterisk/sounds/custom
sudo cp welcome.wav /var/lib/asterisk/sounds/custom/

Step 3 — Set Correct File Permissions

sudo chown asterisk:asterisk /var/lib/asterisk/sounds/custom/welcome.wav
sudo chmod 644 /var/lib/asterisk/sounds/custom/welcome.wav

Without proper permissions, Asterisk cannot play the file.

Step 4 — Test Playback from Asterisk CLI

asterisk -rvvv
console dial 1000@from-internal

Or create a temporary dialplan test:

[from-internal]
exten => 700,1,Answer()
 same => n,Playback(custom/welcome)
 same => n,Hangup()

Dial 700 to confirm audio works.

Using Custom Prompts in IVR

[main-ivr]
exten => s,1,Answer()
 same => n,Background(custom/welcome)
 same => n,WaitExten(5)

Note: Do not include the .wav extension in Playback/Background.

Common Installation Problems

Prompt Does Not Play

• Wrong file path or name
• Missing permissions
• Unsupported audio format

Caller Hears Silence

• RTP/NAT media problem
• Firewall blocking UDP RTP ports

Audio Sounds Distorted

• Incorrect sample rate
• Stereo instead of mono

Best Practices for Professional Voice Prompts

• Use studio-quality human voice recordings
• Keep messages short and clear
• Normalize audio volume across prompts
• Store prompts in organized subfolders (custom/ivr/, custom/queue/)
• Version-control important prompts for rollback

Prompt clarity directly impacts customer trust and call completion rates.

Security and Maintenance Considerations

• Restrict write access to sounds directory
• Backup custom prompts regularly
• Monitor disk usage in /var/lib/asterisk

Losing prompt files can break IVR and queue flows instantly.

What Comes Next?

After installing prompts, the next step is learning:

• IVR menu navigation logic
• Multi-level IVR routing
• Looping and timeout handling

Key Takeaway

Installing custom prompts correctly ensures reliable IVR playback and professional caller experience.

Always verify:

• Correct WAV format (8 kHz mono)
• Proper directory and permissions
• Successful playback test from dialplan

With these basics in place, your Asterisk IVR becomes stable, clear, and production-ready.