Sound is produced when something vibrates.. The vibration causes the medium around it to vibrate. Vibrations in the air are called longitudinal waves, which can be heard by humans. Sound waves consist of areas of high and low pressure called compressions and rarefactions. The wavelength and the speed of the wave is determined by the pitch or frequency of the sound. Wavelength, frequency, and speed can be determined if you know the other two. The equation speed equals frequency times wavelength is the equation used to do this. Since sound travels at 331 m/s at standard temperature and pressure. Also, longer the wavelength, the lower the pitch. The height of the wave is known as the amplitude. The amplitude determines how loud a sound will be - as amplitude increases loudness increases.