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VanMoof VM_SOUND Analysis

Overview

VanMoof bikes store audio files in a custom VM_SOUND format within the SPI flash memory. These files contain the various sounds used by the bike including bells, alerts, and system notifications.

VM_SOUND Format Structure

VM_SOUND Header: 56 4D 5F 53 4F 55 4E 44 (8 bytes - "VM_SOUND")
Header Data:     FF FF FF FF 01 58 58 58 58 00 58 58 58 58 58 58 6C 54 00 00 (20 bytes)
WAV Data:        52 49 46 46... (RIFF header + audio data)
End Marker:      FF FF FF FF FF (5 bytes) OR 00 00 00 00 00 (5 bytes)

Header Breakdown

56 4D 5F 53 4F 55 4E 44  - "VM_SOUND" magic (8 bytes)
FF FF FF FF               - Unknown/padding (4 bytes)
01                        - Version/type flag (1 byte)
58 58 58 58               - Unknown data (4 bytes)
00                        - Separator/null (1 byte)
58 58 58 58 58 58         - Unknown data (6 bytes)
6C 54 00 00               - WAV data size (4 bytes, little endian)
52 49 46 46               - RIFF header start (WAV data begins)

Size Field Calculation

The 4-byte size field at offset 24-27 indicates WAV data length:

  • 6C 54 00 00 = 0x0000546C = 21,612 bytes
  • 0A 1F 04 00 = 0x00041F0A = 270,090 bytes

To calculate: WAV_size_decimal → hex → reverse_bytes (little endian)

The VM_SOUND format is a simple header prepended to standard WAV files, not a proprietary wrapper.

Audio Properties

Most VanMoof sound files use:

  • Sample Rate: 44.1 kHz (CD quality)
  • Bit Depth: 16-bit PCM
  • Channels: Mono (1 channel)
  • Format: Standard WAV/RIFF format embedded within VM_SOUND wrapper

Tool Usage

Export VM_SOUND Files (Binary)

./cmd -f dump.rom -sounds

Exports raw VM_SOUND files with headers intact.

Extract WAV Files

./cmd -f dump.rom -wav

Extracts playable WAV files by finding RIFF headers within VM_SOUND data.

Analyze Audio Properties

./cmd -f dump.rom -analyze-wav

Shows detailed audio information:

  • Sample rate, bit depth, channels
  • Duration and file size
  • Detects corrupted files

Common Issues

Corrupted Upload Data

Failed firmware updates can leave corrupted VM_SOUND entries containing debug text instead of audio:

Pattern: 00 C0 46 C0 repeating throughout the data Content: ASCII text like "source/tasks/audiotask.c" and error messages Detection: Tool automatically identifies and warns about these corrupted entries

Multiple End Markers

Different firmware versions use different end markers:

  • Older versions: FF FF FF FF FF
  • Newer versions: 00 00 00 00 00

The tool automatically detects both patterns.

Memory Layout

VM_SOUND files are typically located at these SPI flash offsets:

0x0280000 - VM_SOUND #1
0x0300000 - VM_SOUND #2
0x0380000 - VM_SOUND #3
...
(Additional sounds at various offsets)

Sound Types

Based on analysis, VanMoof bikes typically contain:

  1. Bell sounds (various tones and melodies)
  2. System alerts (lock/unlock confirmations)
  3. Error notifications (warning beeps)
  4. Status sounds (power on/off, charging)

Duration ranges from ~1.3 seconds to ~20 seconds depending on the sound type.

Technical Notes

  • VM_SOUND is a simple header format prepended to standard WAV files
  • The actual audio data is standard RIFF/WAV format
  • Some entries may be placeholders or corrupted from failed updates
  • Audio quality is consistent across all valid sound files (44.1kHz/16-bit/mono)