Stethoscope Filter Selection

Your Thinklabs One Digital Stethoscope offers a revolutionary change in filtering sound for auscultation. Instead of the limited Bell/Diaphragm selection, you get multiple filters. (Actual filters can change between software revisions.)

    Sounds comprise a combination of lower and higher pitched sounds. Some sounds, such as S3 heart sounds, contain very low frequencies (low-pitched), valve clicks have somewhat midrange frequencies, and lung sounds and wheezes contain much higher frequencies.

    The filter charts show the extent to which a given range of frequencies are amplified or allowed to pass, and which are attenuated or blocked. The higher the graph, the more that frequency is passed through for you to listen.

    Notice that the mauve graphic extends to a lower frequency before it begins to drop off sharply. This means that lower frequencies will be audible using the mauve filter (ooo---) - better for low heart sounds. Conversely, selecting the cyan filter (---ooo) will allow higher frequencies to be audible (better for lungs).

    Note that there is a tradeoff between hearing higher frequencies and filtering out ambient sound. Ambient noise

tends to be higher frequency, so it's advantageous to filter out higher frequencies to eliminate background noise, but it can also attenuate higher pitched breath sounds.

    Play with different filters and this will become apparent.