VCP 411: Medicine Section

PRINCIPLES OF AUSCULTATION

• The source of every sound is a vibrating body which produces a series of waves in surrounding medium i.e. air. Usually waves are vibrating at the same rate as that of the vibrating body and reach the ears causing vibrations of the eardrums and middle ear producing the sensation of sound. Sounds are divided into tones and notes. Tones have generally recognizable musical quality and have three well-defined characteristics.
• Intensity : the intensity of a tone depends upon the amplitude of the vibrations. A loud tone has wider amplitude of vibrations than a soft tone. E.g. tone over the lung is louder than that over the liver, since the lung is a more elastic tissue and vibrates more readily when struck.
• Pitch : or tonality – depends upon the number of vibrations produced. The frequency is depend on the size of device. When the vibrations are rapid the pitch is higher than when they are slower.
• Quality : The quality of tone is characteristic – however the quality of tone that is the harmonic content is depend on the mechanical properties of the resonator.