Why sound moves at this speed
Liquids are far stiffer (less compressible) than gases, so even though they are denser, sound moves several times faster through them.
Travel times and wavelengths
Over 100 m, sound in mercury takes 69 ms; over a mile, 1.11 s. At concert pitch A4 (440 Hz) the wavelength is 3.30 m, and at 1 kHz it is 1.45 m.
Acoustic impedance
Acoustic impedance (density × speed) is about 19,624,300 rayl (19.6 MRayl). Because it is so different from air's ~413 rayl, about 99.99% of sound energy is reflected at an air–mercury 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 mercury?
1,450 m/s (20 °C).
How long does sound take to travel 1 km through mercury?
About 0.690 seconds.
Is sound faster in mercury than in air?
Yes – 1,450 m/s versus 343 m/s in air at 20 °C.