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Page 19 of 26
Listening with the ds32a
The ds32a Probe uses Electromagnetic Diaphragm (EmD) technology which
has some important characteristics that should be understood to achieve
optimal performance.
This background information is provided simply to enrich your
understanding of the ds32a, so that you can obtain maximum benefit from
its features. Read this section while experimenting with your ds32a,
and this background information will become obvious and self-evident.
If the explanation below seems complicated, rest assured using the ds32a stethoscope is very
simple.
Diaphragm Pressure and Frequency Response
The EmD Diaphragm is pressure-modulated i.e. pressure controls the
mechanical and electrical parameters of the EmD sensing system thereby
changing the frequency response and sensitivity. The user can
significantly alter the sound by adjusting diaphragm pressure. Learn
how to use this to advantage during patient examination - it is a
powerful, tactile way to control the sound you hear, and adjust the
sensitivity for each patient examination. With a little practice, you
will soon be able to control the way you listen, to elicit maximum
benefit.
Apply the Probe to the chest, make subtle changes in diaphragm
pressure, and listen to the effects. The following control is possible:
- Light Pressure - This is usually optimal for most listening. Apply
sufficient pressure to get good skin contact and a clear signal, but do
not push too hard.
- Increasing Pressure - Gently increasing pressure will increase the
sensitivity of the EmD sensor, making sounds louder. This is useful for
listening to obese patients, listening for faint bruits, etc. However,
the combination of loud body sounds (such as listening to the heart at
the apex on a thin patient) and increased pressure (high sensitivity)
can produce distortion due to excessive signal levels in the sensor. It
is therefore not necessary to increase sensitivity when sounds are
already loud and clear. Apply diaphragm pressure according to the
patient and the probe position. The purpose is to provide a tool so
powerful and flexible that its characteristics are suitable for a wide
range of patients and body sounds.
- Significant Pressure - With sufficiently high pressure, the diaphragm
makes contact with the sensing plate behind it, and diaphragm vibration
is restricted. At that point, low frequencies are attenuated, and you
will hear breath sounds over heart sounds. This can be a useful mode
for reducing heart sounds to listen to other sounds, however care
should be taken not to work in this mode when heart sounds are the
sounds of interest. If low frequencies suddenly become attenuated due
to excess pressure, simply back off diaphragm pressure slightly.
Within a short time, it will become intuitive to adjust the
Probe/diaphragm pressure for a particular examination and you will
enjoy the control that you have over sound characteristics.
 Holding the Probe - steady pressure
It is helpful to hold the Probe with a consistent pressure, so that
sound can be controlled as described above. One method is to hold the
Probe so that the fingers also touch the patient chest wall (such as
the left edge of the thumb and the fingertips in the figure.) The Probe
and chest wall then move in unison, with a consistent, light diaphragm
pressure. This is merely one grip - you will find your own personal
preferences for optimally using your ds32a.
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