What factors affect the speed of sound in air?

The speed of sound in air at 20 degrees Celsius (68 degrees Fahrenheit) is 343 metres per second. That is 1126.5 feet per second. Notice: The speed of sound changes with temperature and

a little bit with humidity − but not with air pressure (atmospheric pressure).

The Words "sound pressure at sea level" are incorrect and misleading.

The temperature indication, however, is absolutely necessary.