Why Audio Encoding?
Audio puzzles stand out from text-based challenges and offer unique solving experiences:
- Multimedia appeal — Different from typical text puzzles
- Historical context — Morse and DTMF have rich backgrounds
- Accessibility variation — Works well for audio-capable devices
- Memorable experience — Solvers remember audio puzzles
Audio Encoding Methods
Morse Code Audio
Classic dots and dashes as audio tones. Universally recognised and well-documented.
Best for: Radio themes, military history, SOS scenarios
DTMF Tones
Touch-tone phone sounds. Each digit has a unique dual-frequency tone.
Best for: Phone/tech themes, 80s nostalgia, spy puzzles
Musical Notes
Musical scale notes (A-G) can encode letters. Note frequencies can encode numbers.
Best for: Music-themed caches, concert venues
Rhythm/Beat Patterns
Number of beats, pauses, or rhythm patterns encode information.
Best for: Drum circles, percussion themes
Creating Morse Code Audio
Morse code is the most accessible audio encoding. Use our Morse Audio Generator to create the audio file.
Standard Morse Timing
- Dit (dot): 1 unit
- Dah (dash): 3 units
- Between elements: 1 unit silence
- Between letters: 3 units silence
- Between words: 7 units silence
Speed Considerations
- Beginner friendly: 5-8 WPM (words per minute)
- Standard: 12-15 WPM
- Challenge: 18-25 WPM (for experienced operators)
Tip: Start slow. Most geocachers aren't Morse experts. 8 WPM is challenging enough for most solvers.
Creating DTMF Puzzles
DTMF (Dual-Tone Multi-Frequency) creates those familiar phone button sounds. Perfect for encoding phone numbers or coordinates.
Using DTMF for Coordinates
N 51° 23.456 can be encoded as tones:
5 - 1 - * - 2 - 3 - * - 4 - 5 - 6
Use * as a separator between number groups
Tool: Use our DTMF Encoder to generate and decode tone sequences.
Creating Audio Files
Several methods to create your puzzle audio:
Online Generators (Easiest)
- Use CacheHack's Morse Audio Generator
- Online DTMF tone generators
- Text-to-Morse converter websites
Audio Software (More Control)
- Audacity (free) - generate tones and edit
- GarageBand (Mac) - musical approach
- Online tone generators + audio editor
Physical Recording
- Record actual Morse key sounds
- Record phone button presses
- Adds authenticity but harder to edit
Hosting Your Audio
Your audio file needs to be accessible to solvers. Options include:
- SoundCloud: Free hosting, embeddable player, easy sharing
- YouTube (unlisted): Upload audio with a static image, share link
- Dropbox/Google Drive: Direct file links, but may require download
- Personal website: Full control, but requires hosting
Important: Test your link on multiple devices. Ensure mobile users can play the audio without issues.
Complete Example Puzzle
Cache Title: "The Last Transmission"
Cache description:
"In 1942, a radio operator sent one final message before the station went silent. The coordinates to the drop point were never written down—only transmitted. Listen carefully to the recording we recovered."
[Link to audio file: 20 seconds of Morse code at 8 WPM]
"The message format is: N [degrees] [decimal minutes] W [degrees] [decimal minutes]"
Behind the scenes:
The Morse audio spells out: "N FIVE ONE TWO THREE FOUR FIVE SIX W ZERO ZERO ONE TWO THREE FOUR FIVE SIX"
Decoded: N 51° 23.456, W 001° 23.456
Difficulty Variations
Easy (D2-D2.5)
- State clearly that it's Morse or DTMF
- Slow speed (5-8 WPM for Morse)
- Short message (just the numbers)
- Provide a link to a decoder tool
Medium (D3-D3.5)
- Don't identify the audio type
- Medium speed (10-15 WPM)
- Longer message with context
- Add background noise or effects
Hard (D4+)
- Fast speed or non-standard timing
- Multiple audio encoding types combined
- Heavy audio processing or degradation
- Requires spectral analysis
Pro Tips
- Keep files small. Large files are slow to download on mobile data. Under 2MB is ideal.
- Test on headphones and speakers. Audio sounds different on different devices.
- Provide replay ability. Solvers will need to listen multiple times. Ensure the hosting allows easy replay.
- Have a backup. If your hosting goes down, have another way for solvers to access the audio.
- Consider accessibility. Provide a text alternative or hint for hearing-impaired solvers.