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Liquid · Speed of sound

Speed of sound in seawater

Sound travels through seawater at about 1,500 metres per second (5,400 km/h, 3,355 mph) – 4.4 times faster than in air. Conditions: typical; 1,450–1,570 m/s with depth, salinity and temperature.

1,500 m/sSpeed of sound
5,400 km/hKilometres per hour
4.37×Compared with air
0.667 sTime to travel 1 km

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 seawater takes 66.7 ms; over a mile, 1.07 s. At concert pitch A4 (440 Hz) the wavelength is 3.41 m, and at 1 kHz it is 1.50 m.

Acoustic impedance

Acoustic impedance (density × speed) is about 1,537,500 rayl (1.54 MRayl). Because it is so different from air's ~413 rayl, about 99.89% of sound energy is reflected at an air–seawater boundary – which is why airborne sound hardly enters water or walls, and why ultrasound scans need gel.

Speed of sound in other materials

MaterialSpeedvs. air
Carbon dioxide267 m/s0.78×
Argon323 m/s0.94×
Oxygen326 m/s0.95×
Air at 0 °C331 m/s0.97×
Air343 m/s1.00×
Nitrogen349 m/s1.02×
Methane446 m/s1.30×
Cork500 m/s1.46×
Helium1,007 m/s2.94×
Ethanol1,162 m/s3.39×
Hydrogen1,310 m/s3.82×
Olive oil1,430 m/s4.17×
Mercury1,450 m/s4.23×
Fat tissue1,450 m/s4.23×
Fresh water1,481 m/s4.32×
Seawater1,500 m/s4.37×
Soft tissue (average)1,540 m/s4.49×
Blood1,570 m/s4.58×
Muscle1,580 m/s4.61×
Glycerol1,904 m/s5.55×
Lead2,160 m/s6.30×
Polystyrene2,350 m/s6.85×
Nylon2,600 m/s7.58×
Acrylic (PMMA)2,730 m/s7.96×
Gold3,240 m/s9.45×
Pine (along the grain)3,300 m/s9.62×
Tin3,320 m/s9.68×
Concrete3,600 m/s10.50×
Silver3,650 m/s10.64×
Oak (along the grain)3,850 m/s11.22×
Ice3,880 m/s11.31×
Bone (cortical)4,080 m/s11.90×
Zinc4,210 m/s12.27×
Brass4,400 m/s12.83×
Copper4,760 m/s13.88×
Tungsten5,220 m/s15.22×
Nickel5,600 m/s16.33×
Glass (Pyrex)5,640 m/s16.44×
Stainless steel5,790 m/s16.88×
Steel5,960 m/s17.38×
Granite6,000 m/s17.49×
Titanium6,070 m/s17.70×
Aluminium6,320 m/s18.43×
Diamond12,000 m/s34.99×
Beryllium12,890 m/s37.58×

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 seawater?

About 1,500 m/s (typical; 1,450–1,570 m/s with depth, salinity and temperature).

How long does sound take to travel 1 km through seawater?

About 0.667 seconds.

Is sound faster in seawater than in air?

Yes – 1,500 m/s versus 343 m/s in air at 20 °C.