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Spank uses the --min-amplitude flag to control how sensitive the accelerometer detection is. This determines the minimum g-force required to trigger an audio response.

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The min-amplitude Flag

sudo spank --min-amplitude 0.3
Flag Definition: main.go:200 
cmd.Flags().Float64Var(&minAmplitude, "min-amplitude", 0.3, "Minimum amplitude threshold (0.0-1.0, lower = more sensitive)")
Default value: 0.3Valid range: 0.0 to 1.0Lower values = more sensitive (detects lighter taps)Higher values = less sensitive (requires harder impacts)

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How It Works

When the accelerometer detects motion, Spank calculates the amplitude (g-force magnitude) of the impact. The audio only plays if:
  1. The amplitude exceeds the --min-amplitude threshold
  2. At least 750ms has passed since the last sound (cooldown)
Code Reference: main.go:336-338 
if ev.Amplitude < minAmplitude {
    continue
}
The amplitude represents the acceleration force measured in g-force (where 1.0 = Earth’s gravity).

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Validation

Spank validates the min-amplitude value at startup. Values outside the 0.0-1.0 range will cause an error. Code Reference: main.go:226-228 
if minAmplitude < 0 || minAmplitude > 1 {
    return fmt.Errorf("--min-amplitude must be between 0.0 and 1.0")
}
Choose a sensitivity level based on your use case:
Values: 0.05 - 0.15
sudo spank --min-amplitude 0.1
Best for:
  • Detecting light taps and gentle touches
  • Testing the accelerometer response
  • Very reactive setups
Considerations:
  • May trigger on keyboard typing or normal movement
  • Could produce false positives from vibrations
  • More frequent audio playback

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Combining with Modes

The --min-amplitude flag works with all modes: 
sudo spank --min-amplitude 0.25

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Real-Time Output

When a slap is detected, Spank logs the amplitude to help you tune your sensitivity: 
slap #1 [moderate amp=0.32000g] -> audio/pain/001.mp3
slap #2 [strong amp=0.55000g] -> audio/pain/007.mp3
slap #3 [weak amp=0.28000g] -> audio/pain/003.mp3
The amp=X.XXXXXg shows the detected g-force. Use this to:
  • Increase threshold: If you see unwanted triggers with low amplitudes
  • Decrease threshold: If your slaps show high amplitudes but don’t trigger
Code Reference: main.go:343 
fmt.Printf("slap #%d [%s amp=%.5fg] -> %s\n", num, ev.Severity, ev.Amplitude, file)

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Troubleshooting

Problem: Your slaps aren’t registeringSolution: Lower the min-amplitude value
# Try progressively lower values
sudo spank --min-amplitude 0.2
sudo spank --min-amplitude 0.15
sudo spank --min-amplitude 0.1
Observe the console output to see detected amplitudes and adjust accordingly.
Problem: Normal typing or movement triggers soundsSolution: Raise the min-amplitude value
# Try progressively higher values
sudo spank --min-amplitude 0.35
sudo spank --min-amplitude 0.4
sudo spank --min-amplitude 0.5
Monitor the console to see what amplitudes are causing false positives.
Problem: Some slaps trigger, others don’tPossible causes:
  • Slapping with inconsistent force
  • Laptop on soft surface (absorbs impact)
  • 750ms cooldown preventing rapid slaps
Solution:
  • Use consistent force when testing
  • Place laptop on hard surface
  • Wait at least 750ms between slaps

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Testing Your Settings

To find your ideal sensitivity:
  1. Start with default: sudo spank
  2. Slap your laptop a few times with varying force
  3. Observe the amplitude values in the console output
  4. Adjust the threshold:
    • If values are mostly above 0.4: try --min-amplitude 0.35
    • If values are around 0.2-0.3: keep default 0.3
    • If values are below 0.2: try --min-amplitude 0.15
The amplitude values you see in console output are the actual g-forces detected. Use these to set a threshold that matches your desired sensitivity level.

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