Ping Test
Also: Ring Test, Bell Test, Coin Ping, Sound Test
The ping test is a non-destructive authenticity check in which the characteristic ringing sound of a coin when lightly struck is used to distinguish genuine precious metal coins from counterfeits.
The ping test is one of the oldest and simplest methods for verifying the authenticity of precious metal coins. Silver, gold, and platinum possess a characteristic acoustic property due to their crystalline metal structure: when lightly struck, they vibrate at a high, long-sustained frequency — a bright, clear tone that rings for several seconds. Counterfeit coins made from inferior alloys or with a tungsten core, by contrast, produce a dull, short sound with no sustained ring. Additional testing methods such as density testing or the magnet test should be used as complementary checks.
Physical Background
The sound of a coin is determined by its natural frequency, which depends on its material, mass, geometry, and alloy composition. Precious metals such as silver and gold have a high speed of sound in the solid state and low internal damping (damping coefficient). The result is a long, bright ring. Counterfeit materials such as copper-zinc alloys, lead, or tungsten dampen sound more strongly, causing the tone to be either noticeably lower in pitch, shorter, or tinny.
| Metal | Speed of sound (approx.) | Tonal character |
|---|---|---|
| Silver (999) | 3,650 m/s | Bright, long-ringing |
| Gold (999) | 3,240 m/s | Warm, medium-length ring |
| Copper | 3,810 m/s | Similarly bright, but shorter decay |
| Tungsten | 5,180 m/s | High, hard sound — no harmonic decay |
| Lead | 1,210 m/s | Very dull, no sustained ring |
Note: The tungsten sound is not trivially distinguishable — since tungsten has a density very similar to that of gold (tungsten: 19.25 g/cm³, gold: 19.32 g/cm³), the ping test has limited reliability for gold-plated tungsten counterfeits. In such cases, ultrasound testing or X-ray fluorescence analysis is essential.
How to Perform the Test
The ping test requires no equipment but can be made considerably more precise with a smartphone app:
- Freehand method: Balance the coin on a fingertip or fingernail (minimal damping from body contact). Lightly tap it with the edge of another coin, a pencil, or a fingernail. Listen to the tone and pay attention to its duration, pitch, and clarity.
- App-assisted method (recommended): Apps such as Bullion Test or CoinScan record the sound via microphone and compare the frequency spectrum against reference values for known coin types. A deviation of more than a few hertz in the fundamental tone can indicate a counterfeit.
- Comparison method: Hold a genuine reference coin of the same type and weight alongside the suspect coin and compare both sounds directly.
Fundamental frequency f ≈ (speed of sound v) / (2 × coin diameter d)
Example silver ounce (d ≈ 40 mm): f ≈ 3,650 m/s / 0.08 m ≈ 45,625 Hz (overtone spectrum)
The actual audible fundamental frequency is considerably lower due to the complex geometry of the coin (typically 1,000–6,000 Hz for common bullion coins), but the principle remains the same.
Limitations of the Method
The ping test is a useful quick filter, not conclusive proof. It fails for:
- Tungsten-gold counterfeits (same density, similar acoustic properties at certain geometries)
- Coins with core damping caused by air inclusions or voids (rare high-quality counterfeits)
- Damaged or heavily oxidised coins whose acoustic properties have been altered
- Coins in capsules or blister packs where the test is dampened by packaging material
For a reliable result, the ping test should always be combined with coin weight verification, dimensions checking, and where possible the coin authenticity checker. For high-value items, professional methods such as X-ray fluorescence or ultrasound at a recognised refinery are recommended.
In Brief
The ping test is a quick, cost-free first check for precious metal coins and provides good indications of obvious counterfeits in gold and silver coins — it does not, however, replace instrument-based testing, especially not for tungsten-based counterfeits or high-value numismatic pieces.