Contrary to the often‐made assumption that the addition of moisture increases the velocity of sound in air, these results show that as moisture is added to dry air the velocity of sound at first decreases. The velocity is minimum at a relative humidity (RH) of about 14%; then it rises.

The speed of sound is affected by temperature and humidity. Because it is less dense, sound passes through hot air faster than it passes through cold air. The attenuation of sound in air is affected by the relative humidity. Dry air absorbs far more acoustical energy than does moist air.

Sound travels faster in humid air as compared to dry air. Humidity has a small, but measurable effect on sound speed. Sound travels slightly (0.1%-0.6%) faster in humid air.

The speed of sound can change when sound travels from one medium to another. However, the frequency usually remains the same because it is like a driven oscillation and has the frequency of the original source. That is, because vw = fλ, the higher the speed of a sound, the greater its wavelength for a given frequency.

Air pressure has no effect at all in the speed of sound, in an ideal gas approximation. This is because pressure and density both contribute to the velocity of sound equally, and in an ideal gas, both effects cancel out each other leaving just the effect of temperature.

When the sound pressure in the low pressure phase of the sound wave becomes low enough, the medium through which the sound is traveling ruptures or cavitates. The low pressure puts the medium in tension, generating bubbles. Bubbles produce sound when they collapse.