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Tissue · Speed of sound

Speed of sound in bone (cortical)

Sound travels through bone (cortical) at about 4,080 metres per second (14,688 km/h, 9,127 mph) – 11.9 times faster than in air. Conditions: typical; 3,500–4,100 m/s.

4,080 m/sSpeed of sound
14,688 km/hKilometres per hour
11.90×Compared with air
0.245 sTime to travel 1 km

Why sound moves at this speed

Soft tissues behave acoustically much like water. Medical ultrasound machines assume 1,540 m/s to convert echo times into distances.

Travel times and wavelengths

Over 100 m, sound in bone (cortical) takes 24.5 ms; over a mile, 394 ms. At concert pitch A4 (440 Hz) the wavelength is 9.27 m, and at 1 kHz it is 4.08 m.

Acoustic impedance

Acoustic impedance (density × speed) is about 7,752,000 rayl (7.75 MRayl). Because it is so different from air's ~413 rayl, about 99.98% of sound energy is reflected at an air–bone (cortical) 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 bone (cortical)?

About 4,080 m/s (typical; 3,500–4,100 m/s).

How long does sound take to travel 1 km through bone (cortical)?

About 0.245 seconds.

Is sound faster in bone (cortical) than in air?

Yes – 4,080 m/s versus 343 m/s in air at 20 °C.