The Seven Acoustic Signs of Varroa Stress

These seven acoustic signs appear before visual symptoms and give beekeepers a reliable early-warning system. Each sign reflects a specific physiological strain inside the colony, detectable through your three recording windows.

The Seven Signs

1. 60 Hz Mismatch

Healthy colonies:

brood‑care hum aligns with environmental baseline
stable harmonic ladder
no drift in midband

Early stress indicators:

mismatch between brood hum and environmental tone
slight wobble in harmonic ladder
early brood‑load strain

2. Midband Thinning

Healthy colonies:

dense midband activity
strong WorkEngine
stable brood-care rhythms

Early stress indicators:

midband loss
reduced brood-care tone
early metabolic strain

3. Upper‑Midband Thinning (UMB)

Healthy colonies:

clear upper-midband harmonics
strong brood-temperature tone

Early stress indicators:

thinning in upper-midband
reduced harmonic clarity
brood-load pressure

4. Harmonic Fray

Healthy colonies:

clean harmonic ladder
stable multiples

Early stress indicators:

frayed harmonics
unstable multiples
early brood-care disruption

5. Fundamental Sag

Healthy colonies:

strong fundamental hum
stable warm-up curve

Early stress indicators:

weakened fundamental
sagging tone
colony fatigue

6. Structural Drift

Healthy colonies:

stable tone architecture
consistent midband structure

Early stress indicators:

drifting tone shape
unstable midband
early colony imbalance

7. Ventilation Scatter

Healthy colonies:

clean ventilation tone
stable airflow rhythm

Early stress indicators:

scattered ventilation tone
irregular airflow pattern
colony strain