Diaphragm Pressure & Stethoscope Frequency Response

The Thinklabs Electromagnetic Diaphragm maintains the tactile sense of an acoustic stethoscope, where diaphragm pressure was always used to adjust the sensitivity to lower or higher frequencies. But Thinklabs takes this to a new level.

    The stethoscope diaphragm sits in front of a conductive plate inside the stethoscope body. Vibration is sensed when the diaphragm vibrates and the gap between the diaphragm and the plate behind it changes due to diaphragm vibration.

    Body sounds cause very small gap changes. Pressure you apply against the patient has a far greater effect on the gap between diaphragm and the plate. The chart shows how frequency sensitivity changes as you push harder, reducing the gap - sensitivity changes from the blue to purple to pink graph. Notice how the low frequency (bass sounds) increase?

    When you listen, as you apply more pressure, low-pitched sounds get louder. HOWEVER, when you push hard enough for the diaphragm and plate to touch, vibration will decrease, and you will no longer hear low pitched sounds as intensely. This can be helpful to reduce heart sounds when listening to lungs. But generally, apply enough pressure to find a "sweet spot" where sounds are rich and loud.

NOTE - Changing diaphragm pressure and thereby changing the gap produces very large signals that can "clip" the sound. So make gentle changes in pressure and generally apply a steady, consistent pressure to avoid clipped sounds.