1 What Is an IVR Auto Attendant?
An IVR (Interactive Voice Response) auto attendant is a phone system feature that greets callers with a recorded message and presents them with menu options. When a caller dials your business number, instead of hearing endless ringing or going directly to a receptionist, they hear something like: "Thank you for calling Acme Corp. Press 1 for Sales, Press 2 for Support, or Press 0 for the operator."
With a proper asterisk IVR setup, even a one-person business can project the image of a larger, more established company. Callers get routed to the right person or department immediately, reducing hold times and improving the overall customer experience.
Key Benefits of an Auto Attendant
- Professional greeting for every caller, 24/7
- Automatic call routing without a live receptionist
- After-hours handling with voicemail or alternate routing
- Dial-by-name directory for callers who know their party
- Scalable -- easily add departments as you grow
Asterisk, the open-source PBX framework, provides all the building blocks you need to create a fully customized asterisk menu system. Combined with a reliable SIP trunk for PSTN connectivity, you can build an enterprise-grade phone system at a fraction of the cost of proprietary solutions.
2 Planning Your Call Flow
Before writing a single line of dialplan, sketch out your entire call flow on paper or a whiteboard. A well-planned IVR is the difference between happy callers and frustrated ones who hang up. Map every path from the initial greeting through each option to its final destination.
Incoming Call
|
[Check Business Hours]
|
+---+---+
| |
OPEN CLOSED
| |
[Main [After-Hours
Menu] Message]
| |
+--+--+ [Voicemail]
| | |
1 2 3
| | |
Sales Support Directory
| |
[Queue] [Queue]
| |
[Agent] [Agent]Call Flow Checklist
Questions to Answer
- - How many departments or options?
- - What happens on timeout?
- - What happens on invalid input?
- - Is there an after-hours message?
- - Do callers need a dial-by-name option?
- - Should option 0 reach a live person?
Best Practices
- - Keep the main menu to 4-5 options max
- - Put the most popular option first
- - No more than 2 levels of sub-menus
- - Always provide a way to reach a human
- - Keep prompts under 30 seconds
- - State the option before the number
Pro Tip: Say "For Sales, press 1" rather than "Press 1 for Sales." Callers hear the department name first and remember the number better.
3 Recording IVR Prompts
Quality audio prompts are essential for a professional auto attendant asterisk system. Poor recordings reflect badly on your business. Asterisk supports several audio formats, but the telephony standard is 8kHz, 16-bit, mono PCM (WAV) or GSM.
Method 1: Recording via SOX (Command Line)
Use SOX to record directly from a microphone and convert to the correct format:
# Record from microphone (Ctrl+C to stop)
rec -r 8000 -c 1 -b 16 main-menu.wav
# Convert an existing recording to Asterisk format
sox input.wav -r 8000 -c 1 -b 16 main-menu.wav
# Convert to GSM format (smaller file size)
sox input.wav -r 8000 -c 1 main-menu.gsm
# Normalize volume levels
sox main-menu.wav main-menu-normalized.wav gain -n -3Method 2: Recording via Asterisk Dialplan
Create a recording extension that lets you record prompts by dialing in:
[record-prompts]
; Dial *99 to record, press # when done
exten => *99,1,Answer()
same => n,Playback(beep)
same => n,Record(/var/lib/asterisk/sounds/custom/recording%d:wav)
same => n,Wait(1)
same => n,Playback(/var/lib/asterisk/sounds/custom/${RECORDED_FILE})
same => n,Hangup()
; Record a specific prompt by name
exten => *98,1,Answer()
same => n,Read(FILENAME,vm-enter-num-to-call,20)
same => n,Playback(beep)
same => n,Record(/var/lib/asterisk/sounds/custom/${FILENAME}:wav)
same => n,Wait(1)
same => n,Playback(/var/lib/asterisk/sounds/custom/${FILENAME})
same => n,Hangup()Audio Format Requirements
| Format | Sample Rate | Channels | Notes |
|---|---|---|---|
| WAV (PCM) | 8000 Hz | Mono (1) | Best quality, larger files |
| GSM | 8000 Hz | Mono (1) | Compressed, good trade-off |
| SLN16 | 16000 Hz | Mono (1) | Wideband, HD voice |
| ulaw/alaw | 8000 Hz | Mono (1) | Native codec format |
Professional Recording Services
For the best impression, consider professional voice-over artists. Services like Snap Recordings, VoiceJungle, or Fiverr voice-over sellers can produce studio-quality prompts for $50-200. They will deliver files in the exact format Asterisk needs. Place recorded files in /var/lib/asterisk/sounds/custom/.