Why sound moves at this speed
In gases, sound speed depends mainly on temperature and the mass of the molecules: light gases such as helium and hydrogen carry sound much faster, which is why helium raises the pitch of your voice's resonances.
Travel times and wavelengths
Over 100 m, sound in argon takes 310 ms; over a mile, 4.98 s. At concert pitch A4 (440 Hz) the wavelength is 73.4 cm, and at 1 kHz it is 32.3 cm.
Acoustic impedance
Acoustic impedance (density × speed) is about 537 rayl (0.000537 MRayl). Gases have impedances close to air, so sound passes between them with little reflection.
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 argon?
About 323 m/s (about 20 °C).
How long does sound take to travel 1 km through argon?
About 3.096 seconds.
Is sound faster in argon than in air?
No – 323 m/s versus 343 m/s in air at 20 °C.