Velocity of Sound in Sea Water (20°C, 10m depth) to Foot per Hour

The speed of sound in seawater at 20°C and 10 meters depth is approximately 1,522 m/s, varying with temperature, salinity, and pressure.

Complex function of T, S, P. Mackenzie equation: c ≈ 1,449 + 4.6T - 0.055T² + 0.00029T³ + (1.34-0.01T)(S-35) + 0.016z. Typical: ~1,500 m/s.

To km/h: × 3.6. To ft/s: × 3.281. 1,522 m/s = 5,479 km/h = 3,404 mph.

Naval sonar, commercial ship echo sounders, underwater positioning systems, and marine seismic surveys.

Sound speed increases ~1.3 m/s per °C, ~1.3 m/s per PSU salinity, and ~1.7 m/s per 100m depth. SOFAR channel at ~1000m depth traps sound for thousands of km.

Using a single constant — sound speed in the ocean varies significantly with depth and location. Always measure or calculate for local conditions.

~1,500 m/s is a good approximation. Remember: warmer, saltier, deeper = faster sound. Critical for accurate sonar ranging.

Foot per hour measures distance in feet traveled over one hour. Used for very slow movements in imperial units.

1 ft/h = 0.000085 m/s = 0.0003048 km/h = 0.3048 m/h.

To ft/s: ÷ 3,600. To mph: ÷ 5,280. To m/s: × 0.000085.

Glacier movement in US studies, very slow industrial processes, and some geological measurements.

Some glaciers move at 50–500 ft/h. Very slow conveyor systems might use this unit.

Confusing with ft/min (60× faster) or ft/s (3,600× faster).

5,280 ft/h = 1 mph. Extremely slow. Rarely used outside specialized contexts.