A graph of the air pressure at a certain point might look like this:

The arrow indicates one cycle of the sound. The time it takes to complete a cycle is the period. Frequency is the inverse of this, the number of cycles in a second. The distance sound travels during one period is the wavelength. All this is related by the formulas:

The upside down y is lambda, which stands for wavelength. P is period, f is frequency, and s is the speed of sound.

The reason we have to be aware of this relationship is that our ears are sensitive to frequency, which we perceive as pitch, but the world works mostly by wavelength. For instance, a trombone manipulates wavelength directly: when the temperature changes, the trombonist must adjust what he does to get the proper pitch.

A 1000 Hz tone has a wavelength a bit under one foot. The wavelength of 440 hz is 2.57 ft or 75.9 cm.