Since sound is a longitudinal wave, the speed of sound depends on how quickly the energy from one particle can get transferred to the next one. At an intuitive level, the more dense an object is, the faster it can propagate sound. As a practical reflection of that, the speed of sound in air is approximately 343 meters per second, but the speed of sound in water is nearly 1500 meters per second. Sound can also travel through solids, and those lead to even higher speeds. For example, the speed of sound in steel is nearly 6000 meters per second.

There are two important characteristics of sound that are related to the speed of sound: frequency and wavelength.

When it comes to a sound wave, frequency is a measure of how often the pattern repeats in time, and it is measured in units of \(\frac{1}{\text{sec}}\text{,}\) which is often called Hertz (Hz). You can intuitively think of this as the number of vibrations per second. This quantity is denoted \(f\text{.}\) Humans can hear sounds from as about 20 Hz to 20,000 Hz. When you hear stringed instruments tuning before a concert, they typically tune to 440 Hz (though this has been different at different times of history and is sometimes different in certain geographical regions).

Wavelength is a measure of how often the pattern repeats in space. In other words, it is the physical distance between repetitions of the waveform. This means that wavelength is measured as a distance, and is denoted as \(\lambda\text{.}\)

The formula that relates these three variables together is \(v = f \lambda\text{.}\) The 440 Hz tone has a wavelength of about 0.78 meters.