Speed of Sound in Water at 20 °C
| Value | 1,482 m/s |
| Status | Measured: ± 1 m/s (0.00067 relative) |
| Source | CRC Handbook of Chemistry and Physics / Crane TP-410 |
| Categories | Material PropertiesEngineering & Trade |
| millimeter per year | 46,768,363,000,000 mm/yr |
| millimeter per day | 128,044,800,000 mm/day |
| millimeter per hour | 5,335,200,000 mm/h |
| inch per day | 5,041,133,900 in/day |
| foot per day | 420,094,490 ft/d |
| inch per hour | 210,047,240 in/h |
| meter per day | 128,044,800 m/d |
| millimeter per minute | 88,920,000 mm/min |
| meter per hour | 5,335,200 m/h |
| inch per minute | 3,500,787.4 in/min |
| millimeter per second | 1,482,000 mm/s |
| foot per minute | 291,732.28 ft/min |
| centimeter per second | 148,200 cm/s |
| meter per minute | 88,920 m/min |
| inch per second | 58,346.457 in/s |
| kilometer per hour | 5,335.2 km/h |
| foot per second | 4,862.2047 ft/s |
| mile per hour | 3,315.1396 mph |
| knot | 2,880.7775 kn |
| meter per second | 1,482 m/s |
| mach (sea level) | 4.3550577 Ma |
| kilometer per second | 1.482 km/s |
| speed of light | 0.0000049434199 c |
Learning zone
Sound speed in a liquid is √(K/ρ), the ratio of bulk modulus to density: 2.18 GPa over 998 kg/m³ gives 1478 m/s, close to the measured 1482. Unlike gases, liquids get faster as they warm, up to a maximum near 74 °C, and seawater is faster still (about 1500 m/s) thanks to salinity. This is the number behind sonar, ultrasonic flow meters, hull thickness gauging and medical ultrasound (soft tissue is near 1540 m/s).
In piping it sets water hammer. The Joukowsky surge Δp = ρ c Δv predicts about 1.5 MPa (215 psi) for every 1 m/s of velocity stopped instantly in a rigid pipe. Real pipes are elastic, and the wave speed in a thin-walled plastic or lined pipe drops to 300–600 m/s, which softens the surge substantially — one of the few genuine advantages of plastic pipe. A few percent of entrained air lowers c dramatically, since the mixture inherits the gas's compressibility and the liquid's density, which is exactly why air chambers and surge vessels work.