phonocardiograph

An instrument, utilizing microphones, amplifiers, and filters, for graphically recording the heart sounds, which are displayed on an oscilloscope or analog tracing.

- linear p. a p. that records all chest wall vibrations resulting from cardiac activity, with emphasis on low-frequency vibrations due to its filter characteristics.

- logarithmic p. a p. that records only theoretically audible vibrations with emphasis on the higher frequencies due to filter characteristics designed to imitate the logarithmic frequency-intensity response of the human auditory apparatus.

- spectral p. an instrument for recording the heart sounds in which the electrical changes created by the latter pass from a microphone through a series of filters, each of which is tuned to a particular frequency band; output from each filter activates a separate light source of brightness proportional to the intensity of the sound transmitted through that filter; the lights are arranged vertically in descending order of frequencies. A record is obtained by photographing the vertical row of lights.

- stethoscopic p. a p. that records all sound vibrations, audible and inaudible, conveyed by the stethoscope; however, very low-frequency vibrations (in the range of body movements) are filtered out.

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pho·no·car·dio·graph -.graf n an instrument used for producing a graphic record of heart sounds and consisting of microphones, an amplifier, and recording equipment

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pho·no·car·dio·graph (fo″no-kahrґde-o-graf) [phono- + cardiograph] the instrument used in phonocardiography, generally comprising a microphone, amplifier, filters, and a recording device.