Acoustic phonetics studies the physical aspects of sounds: those aspects and physical processes occurring in the transmission of physical sounds from the speaker to the listener. A speaker produces sound waves which are then transmitted through the air. As sound waves differ physically according to their amplitude, frequency and intensity, different sounds of language are possible. Instruments exist capable of recording the different physical properties of sounds and acoustic spectrography makes use of such instruments. These instruments produce spectrograms of sounds, each different sound corresponding to a change in the spectrogram. Although it is difficult to distinguish the visual representations of the sounds from one another, the spectrograms do indeed represent speech as a continuum rather that as isolated sounds. For additional information concerning spectrograms and acoustic phonetics, readers are advised to consult Gimson (1992).