Why sound moves at this speed
Solids are very stiff, so sound usually travels fastest through them. Speed rises with stiffness (elastic modulus) and falls with density.
Travel times and wavelengths
Over 100 m, sound in granite takes 16.7 ms; over a mile, 268 ms. At concert pitch A4 (440 Hz) the wavelength is 13.64 m, and at 1 kHz it is 6.00 m.
Acoustic impedance
Acoustic impedance (density × speed) is about 16,200,000 rayl (16.2 MRayl). Because it is so different from air's ~413 rayl, about 99.99% of sound energy is reflected at an air–granite boundary – which is why airborne sound hardly enters water or walls, and why ultrasound scans need gel.
Speed of sound in other materials
| Material | Speed | vs. air |
|---|---|---|
| Carbon dioxide | 267 m/s | 0.78× |
| Argon | 323 m/s | 0.94× |
| Oxygen | 326 m/s | 0.95× |
| Air at 0 °C | 331 m/s | 0.97× |
| Air | 343 m/s | 1.00× |
| Nitrogen | 349 m/s | 1.02× |
| Methane | 446 m/s | 1.30× |
| Cork | 500 m/s | 1.46× |
| Helium | 1,007 m/s | 2.94× |
| Ethanol | 1,162 m/s | 3.39× |
| Hydrogen | 1,310 m/s | 3.82× |
| Olive oil | 1,430 m/s | 4.17× |
| Mercury | 1,450 m/s | 4.23× |
| Fat tissue | 1,450 m/s | 4.23× |
| Fresh water | 1,481 m/s | 4.32× |
| Seawater | 1,500 m/s | 4.37× |
| Soft tissue (average) | 1,540 m/s | 4.49× |
| Blood | 1,570 m/s | 4.58× |
| Muscle | 1,580 m/s | 4.61× |
| Glycerol | 1,904 m/s | 5.55× |
| Lead | 2,160 m/s | 6.30× |
| Polystyrene | 2,350 m/s | 6.85× |
| Nylon | 2,600 m/s | 7.58× |
| Acrylic (PMMA) | 2,730 m/s | 7.96× |
| Gold | 3,240 m/s | 9.45× |
| Pine (along the grain) | 3,300 m/s | 9.62× |
| Tin | 3,320 m/s | 9.68× |
| Concrete | 3,600 m/s | 10.50× |
| Silver | 3,650 m/s | 10.64× |
| Oak (along the grain) | 3,850 m/s | 11.22× |
| Ice | 3,880 m/s | 11.31× |
| Bone (cortical) | 4,080 m/s | 11.90× |
| Zinc | 4,210 m/s | 12.27× |
| Brass | 4,400 m/s | 12.83× |
| Copper | 4,760 m/s | 13.88× |
| Tungsten | 5,220 m/s | 15.22× |
| Nickel | 5,600 m/s | 16.33× |
| Glass (Pyrex) | 5,640 m/s | 16.44× |
| Stainless steel | 5,790 m/s | 16.88× |
| Steel | 5,960 m/s | 17.38× |
| Granite | 6,000 m/s | 17.49× |
| Titanium | 6,070 m/s | 17.70× |
| Aluminium | 6,320 m/s | 18.43× |
| Diamond | 12,000 m/s | 34.99× |
| Beryllium | 12,890 m/s | 37.58× |
Typical longitudinal (bulk) sound speeds at about 20 °C unless stated. Real values vary with composition, temperature, pressure and wave type; thin rods carry slower 'bar' waves.
Frequently asked questions
What is the speed of sound in granite?
About 6,000 m/s (typical; 5,000–6,500 m/s).
How long does sound take to travel 1 km through granite?
About 0.167 seconds.
Is sound faster in granite than in air?
Yes – 6,000 m/s versus 343 m/s in air at 20 °C.