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Solid · Speed of sound

Speed of sound in glass (Pyrex)

Sound travels through glass (Pyrex) at 5,640 metres per second (20,304 km/h, 12,616 mph) – 16.4 times faster than in air. Conditions: borosilicate, bulk.

5,640 m/sSpeed of sound
20,304 km/hKilometres per hour
16.44×Compared with air
0.177 sTime to travel 1 km

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 glass (Pyrex) takes 17.7 ms; over a mile, 285 ms. At concert pitch A4 (440 Hz) the wavelength is 12.82 m, and at 1 kHz it is 5.64 m.

Acoustic impedance

Acoustic impedance (density × speed) is about 12,577,200 rayl (12.6 MRayl). Because it is so different from air's ~413 rayl, about 99.99% of sound energy is reflected at an air–glass (Pyrex) 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 glass (Pyrex)?

5,640 m/s (borosilicate, bulk).

How long does sound take to travel 1 km through glass (Pyrex)?

About 0.177 seconds.

Is sound faster in glass (Pyrex) than in air?

Yes – 5,640 m/s versus 343 m/s in air at 20 °C.